Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
For a lot of people the FFT seems to be the one size fits all solution to any frequency and phase related problem in DSP. It is NOT! For frequency/phase detection comparisons from sets of sampled data the methods explained in http://ipnpr.jpl.nasa.gov/progress_report/42-121/121G.pdf are MUCH more appropiate. Best regards Ulrich Bangert -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Hal Murray Gesendet: Mittwoch, 3. Juni 2009 20:00 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references One of the main problems is that in working at milli-Hz binwidths the FTT word length needs to be very long to cover even a few tens of Hz range and we run into memory problems. I'm missing something. How much memory do you have on your laptop? I'm not a DSP wizard. If you have 10 Hz bandwidth and you want milli-Hz bins, that takes 2x10x1000 samples. Right? I'd expect that to fit easily. That's 20K samples, at 8 bytes each, round up to 10, call it 200K bytes. Jumping to micro-Hz might get interesting. That would be 200 megabytes. Lots of laptops have room for that. Maybe not an old one. Even with an old laptop without much memory, I'd expect you could do several factors of 2 better than milli-Hz bins. On the other hand, how much bandwidth do you really need? Junk crystals are 50-100 ppm. 100 ppm at 1 KHz is 1/10 Hz. So why do you need more than 1 Hz input bandwidth? You can probably get closer than that by calibrating the crystals in your particular gear. Connie's numbers were 250 micro-Hz drift with a 500 micro-Hz offset. (That was with reasonably stable temperature.) So a few milli-Hz bandwidth looks like enough. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Alberto di Bene skrev: Magnus Danielson wrote: Hmm, do you get a feeling that I am actually object very much to just toss it into the processor. I think you are right. :) I suppose you are familiar with the old American adage that says that to a man with a hammer every problem looks like a nail :-) Yes. :o) Each of us is more familiar with one or another technology (broadly speaking), and tend to see it as the best way to solve problems. I am not immune from this... This is why I try to find more tools and more approaches. Nothing wrong with software, but use it wisely. Build the test-benches as if you where doing a ASIC or full-custom design and thus also think about each compile costing you milions of dollars and a pipe-line depth of many months (6-9). Given the rate of compiles that sometimes I do especially when near to find the solution of a problem that bugged me for a long time, I would be bankrupted since long, should each compile cycle cost me thousands or millions of dollars, even if bogus dollars... :-) :-) I think you would learn important lessons in test-benching and overall design before the compile. I guess I am becomming more conservative by the day. From my own and others mistakes and succsesses. This is a privilege of becoming older and wiser :-) Whiee... I got so much to learn then! :) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Lux, James P skrev: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rex Moncur Sent: Tuesday, June 02, 2009 3:06 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Hi all Thank you all for you advice and suggestions re my request. At this stage it does not look like there is a simple solution of a readily available USB sound card that can be locked to a 10 MHz GPSDO reference. The constraints of portable operation with a Laptop rule out a number of solutions. I have tried the software solution using Spectrum Lab but ran into problems and perhaps this just needs more work. One of the main problems is that in working at milli-Hz binwidths the FTT word length needs to be very long to cover even a few tens of Hz range and we run into memory problems. So there is little room to have a reference frequency spaced well away from the frequency range being used. The reference frequency can be right on top of your signal, as long as it's within the dynamic range. You can subtract it out before doing the FFT, after having determined where it is and how big it is. Considering the length of these traces, the local oscillator vs. the reference will shift around. What I would do is to ensure that the reference signal and input signal is either on very different frequencies or different channels. Then, I would in the sampling phase frequency convert the receive signal and reference signal using digital fixed NCO/quadrature oscillators (cos, sin) and do integrate and dump (synchronous dump for both receive and reference signals) processing for low pass filtering and reducing sample rate. Since the signal was fairly narrow banded, this digital receiver approach would significantly reduce the amounts of data while requiring a very reasonable amount of real-time processing. The remaining sample stream still contains the crutial information if sufficient bandwidth is maintained after the integrate and dump processing. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
connie.marsh...@suddenlink.net said: www.k5cm.com/soundcard.htm Nice, thanks. From there: Sound card drift over this four hour period is about 250 micro Hertz. The temp in the shack was going up during the measurement period. Unfortunately I did not track the exact temp rise, but was about around 4 to 6 degrees F. 250 micro Hz relative to 1000 Hz is 1/4 ppm. My memory is that junk PC crystals are ballpark of 1 ppm/degree. (That's probably per degree C rather than F, but that's only a factor of 2.) So 1/4 ppm for 4 degrees is better than I would have guessed. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
One of the main problems is that in working at milli-Hz binwidths the FTT word length needs to be very long to cover even a few tens of Hz range and we run into memory problems. I'm missing something. How much memory do you have on your laptop? I'm not a DSP wizard. If you have 10 Hz bandwidth and you want milli-Hz bins, that takes 2x10x1000 samples. Right? I'd expect that to fit easily. That's 20K samples, at 8 bytes each, round up to 10, call it 200K bytes. Jumping to micro-Hz might get interesting. That would be 200 megabytes. Lots of laptops have room for that. Maybe not an old one. Even with an old laptop without much memory, I'd expect you could do several factors of 2 better than milli-Hz bins. On the other hand, how much bandwidth do you really need? Junk crystals are 50-100 ppm. 100 ppm at 1 KHz is 1/10 Hz. So why do you need more than 1 Hz input bandwidth? You can probably get closer than that by calibrating the crystals in your particular gear. Connie's numbers were 250 micro-Hz drift with a 500 micro-Hz offset. (That was with reasonably stable temperature.) So a few milli-Hz bandwidth looks like enough. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
There is an overbeleif in what software is suitable for IMHO. [Fun discussion. Thanks.] Many years ago, somebody on the FPGA newsgroup pointed out that, in general, if you can do the problem in software that's probably the better way. One of the considerations is that it's easier to hire programmers rather than hardware designers. FPGAs are halfway between real hardware and software. You can try a simple change without any harsh time or cost penalty to make new masks and new chips. If that change is a bug fix, you might think of it as typical sloppy programmer behavior. On the other hand, that change may be a new idea you want to try... For many people in this group, fun is probably the most important consideration. Different things will appeal to different people. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
You know, I probably need to run the test again and do a better job of tracking room temp. My thermometer is high up on the wall in the shack. The computer sets under the bench in a corner. It does represent a typical afternoon in my shack however. 73, Connie K5CM -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Hal Murray Sent: Wednesday, June 03, 2009 12:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references connie.marsh...@suddenlink.net said: www.k5cm.com/soundcard.htm Nice, thanks. From there: Sound card drift over this four hour period is about 250 micro Hertz. The temp in the shack was going up during the measurement period. Unfortunately I did not track the exact temp rise, but was about around 4 to 6 degrees F. 250 micro Hz relative to 1000 Hz is 1/4 ppm. My memory is that junk PC crystals are ballpark of 1 ppm/degree. (That's probably per degree C rather than F, but that's only a factor of 2.) So 1/4 ppm for 4 degrees is better than I would have guessed. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Brian Kirby skrev: I use a Lynx One sound card, it has analog and digital I/O and MIDI I/O and clock I/O. Their manuals are available on line at www.lynxstudio.com. These are profession 24 bit cards, the analog I/O uses balanced interfaces. They handle AES/EBU and SP DIF digital audio formats. The sound card can take an internal clock, an external clock input on the MIDI port, there is a parallel clock header on the PC board, and a digital clock input on the digital audio lines. It can accept a 13.5 Mhz video dot clock, a 27 Mhz video dot clock, and a word clock and word clock/256. 13,5 MHz is ITU-R BT.601/BT.656 luminance sampling rate. 27 MHz is BT.601/BT.656 luminance/chroma-difference combined sampling rate (4:2:2). 27 MHz is the video reference rate of them all. Sad that they broke it when they did the North American HD stuff. Breaking numerology like that isn't very nice... it always cost extra now. I think you mean word-clock * 256 as this is Digidesign/ProTools clock distribution strategy, giving 12,288 MHz for 48 kHz sampling rate. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. -- LART. 250 MIPS under one Watt. Free hardware design files. http://www.lartmaker.nl/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Lux, James P skrev: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rex Moncur Sent: Monday, June 01, 2009 3:00 PM To: 'Discussion of precise time and frequency measurement' Subject: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Hi all Does anyone have any experience of locking a USB external soundcard to a GPSDO 10 MHz reference. I am interested in advice on any good quality soundcards that can be readily locked to either 10 MHz or if necessary to some other frequency that we can derive from a GPSDO source. I have done some tests with the SignalLink soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz lock frequency. This requires some cutting of tracks to remove the internal oscillator feedback and insert the locking frequency. 12 MHz is readily derived from 10 MHz but I have not been able to get it to lock. The Texas instruments data sheet suggests that it is possible to use an external refernce but also says this is not recommended. With this expereicne I would rather find a sound card that is designed for external locking that does not require the cutting of tracks. For info the purpose of this request is that we are looking at using very narrow bandwidth modes at less than 1 mHz for light wave communcation. To date using LEDs and cloud reflection we have worked over 200 km with WSJT but we should be able to do 20 dB better if we can get down to milli-Hz bandwidths (at the expense of spending all night to complete a QSO). Our expereince to date is that standard sound cards are just not stable to better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS locking let us get down to sub milli-Hz levels. Rex VK7MO Some of the pro sound interfaces have a word clock input. There are a variety of things that take a external input and generate a S/PDIF that's properly timed, as well. Lots of boxes will take a S/PDIF sync input (e.g. the Edirol FA-66 which was used by lots of Flex-Radio folk), so maybe that's something you could easily generate from your 10MHz. A chart at Cakewalk shows that MOTU has a USB interface (828MkII) which has a word clock sync. It's going to be a pricey beast though, with 8in/8out ($800?) Even if you have a word clock input, you're going to have to synthesize that from the 10 MHz. Maybe it's easier to just make a S/PDIF which is a MUCH more common sync signal. ( I think S/PDIF is something like 3 MHz) S/P-DIF [iec60958-3] has a baudrate which is 128 x sample rate and a bit rate which is 64 x sample rate, which is inherited properties from AES/EBU [aes3] [tech3250] [iec60958-4]. Locking up a S/P-DIF (128 x sample rate) is about the same job as locking up a superclock (256 x sample rate) or wordclock (1 x sample rate). As long as the signal is samples with low jitter and A/D converted in a good fashion, delivery over S/P-DIF should not be too hard. An ADC is slammed onto a AES/EBU/S/P-DIF chip which is fairly trivial extra work. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, June 02, 2009 10:08 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Some of the pro sound interfaces have a word clock input. There are a variety of things that take a external input and generate a S/PDIF that's properly timed, as well. Lots of boxes will take a S/PDIF sync input (e.g. the Edirol FA-66 which was used by lots of Flex-Radio folk), so maybe that's something you could easily generate from your 10MHz. A chart at Cakewalk shows that MOTU has a USB interface (828MkII) which has a word clock sync. It's going to be a pricey beast though, with 8in/8out ($800?) Even if you have a word clock input, you're going to have to synthesize that from the 10 MHz. Maybe it's easier to just make a S/PDIF which is a MUCH more common sync signal. ( I think S/PDIF is something like 3 MHz) S/P-DIF [iec60958-3] has a baudrate which is 128 x sample rate and a bit rate which is 64 x sample rate, which is inherited properties from AES/EBU [aes3] [tech3250] [iec60958-4]. Locking up a S/P-DIF (128 x sample rate) is about the same job as locking up a superclock (256 x sample rate) or wordclock (1 x sample rate). However, if you're buying an off the shelf audio interface, you're stuck with whatever the mfr is providing for a sync input, and a (very) casual inspection of what's available these days (particularly at low cost) shows that S/PDIF seems to be the most common. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
J.D. Bakker wrote: You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. I am in complete agreement with this kind of solution. Sampling on the second channel a reference signal of known value allows the software to make a simple adjustment. No need to switch on the soldering iron... Never do in hardware what can be done in software :-) 73 Alberto I2PHD ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Hello The Net: For portable operations with a laptop, usually only one input channel is available and it is at mike (not line) level. The alternative to sum the analog reference and the analog signal of interest may be possible if the reference noise can be kept out of the signal of interest bandwidth. Maybe a external USB soundcard with at least 2 input channels is more appropriate. Stan, W1LEFN41sr Cape Cod Alberto di Bene wrote: J.D. Bakker wrote: You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. I am in complete agreement with this kind of solution. Sampling on the second channel a reference signal of known value allows the software to make a simple adjustment. No need to switch on the soldering iron... Never do in hardware what can be done in software :-) 73 Alberto I2PHD ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Lux, James P skrev: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, June 02, 2009 10:08 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Some of the pro sound interfaces have a word clock input. There are a variety of things that take a external input and generate a S/PDIF that's properly timed, as well. Lots of boxes will take a S/PDIF sync input (e.g. the Edirol FA-66 which was used by lots of Flex-Radio folk), so maybe that's something you could easily generate from your 10MHz. A chart at Cakewalk shows that MOTU has a USB interface (828MkII) which has a word clock sync. It's going to be a pricey beast though, with 8in/8out ($800?) Even if you have a word clock input, you're going to have to synthesize that from the 10 MHz. Maybe it's easier to just make a S/PDIF which is a MUCH more common sync signal. ( I think S/PDIF is something like 3 MHz) S/P-DIF [iec60958-3] has a baudrate which is 128 x sample rate and a bit rate which is 64 x sample rate, which is inherited properties from AES/EBU [aes3] [tech3250] [iec60958-4]. Locking up a S/P-DIF (128 x sample rate) is about the same job as locking up a superclock (256 x sample rate) or wordclock (1 x sample rate). However, if you're buying an off the shelf audio interface, you're stuck with whatever the mfr is providing for a sync input, and a (very) casual inspection of what's available these days (particularly at low cost) shows that S/PDIF seems to be the most common. Do they really lock up to the S/P-DIF input? I doubt it for the cheap boards. Rather, they decode the S/P-DIF signal and ship the samples into the DSP. The DSP tends to make very rought sample-rate conversions like dropping samples etc. A lockable board isn't that expensive. You can get them off ebay for instance. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Alberto di Bene skrev: J.D. Bakker wrote: You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. I am in complete agreement with this kind of solution. Sampling on the second channel a reference signal of known value allows the software to make a simple adjustment. Such a double-frequency conversion cancels fairly well the transfer oscillators frequency and jitter, as long as it is sufficienly low. No need to switch on the soldering iron... Never do in hardware what can be done in software :-) Respectfully I disagree. There are tasks which is better managed by software and tasks which is better managed by hardware. In the world of FPGAs, it is also worth mentioning that some tasks is best done there. The big trick is to find a balance between various methods, available resources, partitioning of the problem, doing it on time and achieving the needed performance. There is an overbeleif in what software is suitable for IMHO. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Magnus Danielson wrote: No need to switch on the soldering iron... Never do in hardware what can be done in software :-) Respectfully I disagree. There are tasks which is better managed by software and tasks which is better managed by hardware. In the world of FPGAs, it is also worth mentioning that some tasks is best done there. The big trick is to find a balance between various methods, available resources, partitioning of the problem, doing it on time and achieving the needed performance. Of course you are right, the best solution must be decided case by case. But the biggest plus of the software is that it can be changed on the fly, without an expensive reworking station, and the manual ability to correctly use it. And a side effect is speed : you can test many variants of a solution in a time frame of a few minutes. Not so easily doable with hardware changes. 73 Alberto i2PHD ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Alberto di Bene skrev: Magnus Danielson wrote: No need to switch on the soldering iron... Never do in hardware what can be done in software :-) Respectfully I disagree. There are tasks which is better managed by software and tasks which is better managed by hardware. In the world of FPGAs, it is also worth mentioning that some tasks is best done there. The big trick is to find a balance between various methods, available resources, partitioning of the problem, doing it on time and achieving the needed performance. Of course you are right, the best solution must be decided case by case. But the biggest plus of the software is that it can be changed on the fly, without an expensive reworking station, and the manual ability to correctly use it. And a side effect is speed : you can test many variants of a solution in a time frame of a few minutes. Not so easily doable with hardware changes. This is why we do alot of things in FPGAs today, and in the FPGAs we often put dedicated DSPs of various complexity, often adapted to their task. Keeping quick turn-around is on our mind, but in general, the shorter turn-around, the poorer testing usually happends, and the sloopier design is often found, and the longer it takes to get the job done. In general, a CPU is suitable for doing non-common tasks. More dedicated designs like firmware and hardware is suitable to do things which is essentially the same but happends over and over and over and often at a high speed. Such monotonic tasks just waste energy, space and complexity when done in CPUs. The problem with a generic CPU is that it is generic, so it can do all kinds of tasks, which makes timing-critical bulk-processing tasks problematic to combine with sporadic and possibly high-dynamic processing. Splice the bulk off to some dedicated processing, which can be done in another CPU, and better performance is yielded. There are loads of designs where a few well thought 8-bit processors work together and shine over a more modern fancy design. One such example is found in the SR-620 which has a Zilog Z-8000 processor as main CPU and a Z-80 co-processor which only does the X-Y vector display. The Z-80 has so small program that it is loaded into SRAM from the Z-8000 as it boots. The HP 5334A has actually 3 different 3870 processor, one for overall control, one for measurements and one for GPIB. Hmm, do you get a feeling that I am actually object very much to just toss it into the processor. I think you are right. :) Nothing wrong with software, but use it wisely. Build the test-benches as if you where doing a ASIC or full-custom design and thus also think about each compile costing you milions of dollars and a pipe-line depth of many months (6-9). I guess I am becomming more conservative by the day. From my own and others mistakes and succsesses. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Magnus Danielson wrote: Hmm, do you get a feeling that I am actually object very much to just toss it into the processor. I think you are right. :) I suppose you are familiar with the old American adage that says that to a man with a hammer every problem looks like a nail :-) Each of us is more familiar with one or another technology (broadly speaking), and tend to see it as the best way to solve problems. I am not immune from this... Nothing wrong with software, but use it wisely. Build the test-benches as if you where doing a ASIC or full-custom design and thus also think about each compile costing you milions of dollars and a pipe-line depth of many months (6-9). Given the rate of compiles that sometimes I do especially when near to find the solution of a problem that bugged me for a long time, I would be bankrupted since long, should each compile cycle cost me thousands or millions of dollars, even if bogus dollars... :-) :-) I guess I am becomming more conservative by the day. From my own and others mistakes and succsesses. This is a privilege of becoming older and wiser :-) Cheers, Alberto I2PHD ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Hi all Thank you all for you advice and suggestions re my request. At this stage it does not look like there is a simple solution of a readily available USB sound card that can be locked to a 10 MHz GPSDO reference. The constraints of portable operation with a Laptop rule out a number of solutions. I have tried the software solution using Spectrum Lab but ran into problems and perhaps this just needs more work. One of the main problems is that in working at milli-Hz binwidths the FTT word length needs to be very long to cover even a few tens of Hz range and we run into memory problems. So there is little room to have a reference frequency spaced well away from the frequency range being used. The SP DIF solution seems promising if I can generate the required input. This could perhaps be done with a product that already provides the SP DIF word output and locking that. But that could be just as hard as locking the sound-card in the first place. So at this time I think I will put some more effort into locking the sound card and let you know how I go, hi. Injection locking as suggested by some of you may be the answer. Some people asked for more details of the cloud scatter experiments which area at http://reast.asn.au/optical.php There is also a series of articles on our work in the last 3 and next issue of DUBUS. On the question of Doppler shift from clouds - this is much less than a mHz and not an issue due to the fact that we are using base band and the Doppler only applies to the audio frequency. In addition the very narrow beamwidths (around 2 degrees) mean that the possible paths are all very similar in length. Thanks again to everyone for their input. 73 Rex VK7MO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rex Moncur Sent: Tuesday, June 02, 2009 3:06 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Hi all Thank you all for you advice and suggestions re my request. At this stage it does not look like there is a simple solution of a readily available USB sound card that can be locked to a 10 MHz GPSDO reference. The constraints of portable operation with a Laptop rule out a number of solutions. I have tried the software solution using Spectrum Lab but ran into problems and perhaps this just needs more work. One of the main problems is that in working at milli-Hz binwidths the FTT word length needs to be very long to cover even a few tens of Hz range and we run into memory problems. So there is little room to have a reference frequency spaced well away from the frequency range being used. The reference frequency can be right on top of your signal, as long as it's within the dynamic range. You can subtract it out before doing the FFT, after having determined where it is and how big it is. Some people asked for more details of the cloud scatter experiments which area at http://reast.asn.au/optical.php There is also a series of articles on our work in the last 3 and next issue of DUBUS. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Hi Rex, Here is a plot of my sound card. Maybe I'm just lucky with this particular sound card/computer, but the drift was only about 250 micro Hertz over a four hour period. Also for critical measurements I try to run at 200 Hz center frequency rather than 1000 Hz. Cuts the error by five. Maybe that's not practical for you modulation schema. I did not bother to calibrate the sound card before I started the test so there is about 550 micro Hertz of static error when the test starts. www.k5cm.com/soundcard.htm 73, Connie K5CM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Hi all Does anyone have any experience of locking a USB external soundcard to a GPSDO 10 MHz reference. I am interested in advice on any good quality soundcards that can be readily locked to either 10 MHz or if necessary to some other frequency that we can derive from a GPSDO source. I have done some tests with the SignalLink soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz lock frequency. This requires some cutting of tracks to remove the internal oscillator feedback and insert the locking frequency. 12 MHz is readily derived from 10 MHz but I have not been able to get it to lock. The Texas instruments data sheet suggests that it is possible to use an external refernce but also says this is not recommended. With this expereicne I would rather find a sound card that is designed for external locking that does not require the cutting of tracks. For info the purpose of this request is that we are looking at using very narrow bandwidth modes at less than 1 mHz for light wave communcation. To date using LEDs and cloud reflection we have worked over 200 km with WSJT but we should be able to do 20 dB better if we can get down to milli-Hz bandwidths (at the expense of spending all night to complete a QSO). Our expereince to date is that standard sound cards are just not stable to better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS locking let us get down to sub milli-Hz levels. Rex VK7MO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Soundcards for USB are poor at best. I have a set of PCI cards that were previously made by EMU and they accept external reference input. They no longer make the model I have but perhaps they have another PCI card with an external ref input. I am interested in your modulation technique which allows you to use WSJT. Please let me know exactly what you are doing. I also do not know how you are using 5 milliHertz with WSJT since the group of discrete tones occupy more bandwidth. 73, Jeffrey Pawlan WA6KBL ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
I have seen it talked about (around the LF fraternity, but generally they are stable enough there and just need calibation) a lot but not accomplished yet. How about injection locking the on board oscmaybe gating the feedback with the referencenote I havent tried this? Another technique I have used to shift logic-block oscillators is to vary their supply voltage, they will oscillate from around 3v to well over 5.5v that might enable you to phase lock it using a variable regulator to vcxo to crystal?? Alan G3NYK - Original Message - From: Rex Moncur rmon...@bigpond.net.au To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Monday, June 01, 2009 10:59 PM Subject: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Hi all Does anyone have any experience of locking a USB external soundcard to a GPSDO 10 MHz reference. I am interested in advice on any good quality soundcards that can be readily locked to either 10 MHz or if necessary to some other frequency that we can derive from a GPSDO source. I have done some tests with the SignalLink soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz lock frequency. This requires some cutting of tracks to remove the internal oscillator feedback and insert the locking frequency. 12 MHz is readily derived from 10 MHz but I have not been able to get it to lock. The Texas instruments data sheet suggests that it is possible to use an external refernce but also says this is not recommended. With this expereicne I would rather find a sound card that is designed for external locking that does not require the cutting of tracks. For info the purpose of this request is that we are looking at using very narrow bandwidth modes at less than 1 mHz for light wave communcation. To date using LEDs and cloud reflection we have worked over 200 km with WSJT but we should be able to do 20 dB better if we can get down to milli-Hz bandwidths (at the expense of spending all night to complete a QSO). Our expereince to date is that standard sound cards are just not stable to better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS locking let us get down to sub milli-Hz levels. Rex VK7MO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Hi Jeff Thanks for your advice which I will follow up - the reason for going for a USB sound card is that the system must be operated portable with a Laptop - but perhaps there is a way to use a PCI sound card on a Laptop. While we use WSJT at present we have a new Mode under development for the mill-Hz bandwidth. In testing this new mode is acheiveing around 15 dB better than WSJT with 5 mHz binwidths and should get to 20 dB better with 1 mHz binwidths. It uses M-ary FSK like WSJT but does not need a reference tone for time or frequency locking on the basis that both soundcards are GPS locked. Timing errors are not an issue as the tone durations are 16 mins at 1 mHz binwidth. We use around 20,000 separate M-ary tones (cf 64 for WSJT), which is sufficient to send the first three characters of a call sign in Clark-Karn source encoded format - thus it requires only two tones to be sent to receve a full callsign. However at one mHz bandwidth this takes 16 minutes to send a single tone and thus an hour to send two callsigns. However, we have some shorter techniques for exchanging reports and RRR so a QSO can be comppleted in around 3 hours, hi. We can fit 20,000 tones spaced 1 mHz apart into just 20 Hz so there is not problem there. We have not yet added FEC which should allow a further improvement but we would like to resolve the sound card stablity issues first. 73 Rex VK7MO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
rmon...@bigpond.net.au said: For info the purpose of this request is that we are looking at using very narrow bandwidth modes at less than 1 mHz for light wave communcation. To date using LEDs and cloud reflection we have worked over 200 km with WSJT but we should be able to do 20 dB better if we can get down to milli-Hz bandwidths (at the expense of spending all night to complete a QSO). Our expereince to date is that standard sound cards are just not stable to better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS locking let us get down to sub milli-Hz levels. Sounds like a fun project. Do the clouds shift around enough to cause Doppler problems? You might find something in the way of a DSP or FPGA demo board. (I don't have any suggestions.) Or maybe a demo board for an audio chip. How stable is the osc on your current board? Do you need accuracy or stability? Can you feed a calibration signal in the other stereo channel and sort it out in software? Or tap off some signal in the board and feed that to a counter for calibration. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
The concern I'd have with modifying a USB sound card, or any of them for that matter, is that the glue logic between the ADC and the USB chip may be designed for a certain relationship between the ADC and USB clocks. Running the ADC asynchronously may or may not be robust depending on the assumptions baked into the gate array. It might be OK if your app can tolerate occasional misclocking or dropouts but I'd be reluctant to use a hacked sound card for anything timing-critical. I just (last week) got an AD7760 ADC eval board working with the Digilent Nexys2 FPGA platform, with the EVAL-AD7760 board running from its own 40 MHz clock. It will accept an external 40 MHz clock source that, in turn, wouldn't be hard to derive from 10 MHz. Way overkill for ultra low-bandwidth work, but if anyone is looking for a clean digitizer for audio rates in general, you could do a lot worse than this approach. Cost isn't too bad either, at $130 for the Nexys2 and $150 for the ADC7760 eval board. Of course the big drawback is the lack of any sort of standardized audio driver on the host side. If/when I spin a PCB for this project I'll definitely include a 10 MHz input. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Jeffrey Pawlan Sent: Monday, June 01, 2009 3:08 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Soundcards for USB are poor at best. I have a set of PCI cards that were previously made by EMU and they accept external reference input. They no longer make the model I have but perhaps they have another PCI card with an external ref input. I am interested in your modulation technique which allows you to use WSJT. Please let me know exactly what you are doing. I also do not know how you are using 5 milliHertz with WSJT since the group of discrete tones occupy more bandwidth. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rex Moncur Sent: Monday, June 01, 2009 3:00 PM To: 'Discussion of precise time and frequency measurement' Subject: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Hi all Does anyone have any experience of locking a USB external soundcard to a GPSDO 10 MHz reference. I am interested in advice on any good quality soundcards that can be readily locked to either 10 MHz or if necessary to some other frequency that we can derive from a GPSDO source. I have done some tests with the SignalLink soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz lock frequency. This requires some cutting of tracks to remove the internal oscillator feedback and insert the locking frequency. 12 MHz is readily derived from 10 MHz but I have not been able to get it to lock. The Texas instruments data sheet suggests that it is possible to use an external refernce but also says this is not recommended. With this expereicne I would rather find a sound card that is designed for external locking that does not require the cutting of tracks. For info the purpose of this request is that we are looking at using very narrow bandwidth modes at less than 1 mHz for light wave communcation. To date using LEDs and cloud reflection we have worked over 200 km with WSJT but we should be able to do 20 dB better if we can get down to milli-Hz bandwidths (at the expense of spending all night to complete a QSO). Our expereince to date is that standard sound cards are just not stable to better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS locking let us get down to sub milli-Hz levels. Rex VK7MO Some of the pro sound interfaces have a word clock input. There are a variety of things that take a external input and generate a S/PDIF that's properly timed, as well. Lots of boxes will take a S/PDIF sync input (e.g. the Edirol FA-66 which was used by lots of Flex-Radio folk), so maybe that's something you could easily generate from your 10MHz. A chart at Cakewalk shows that MOTU has a USB interface (828MkII) which has a word clock sync. It's going to be a pricey beast though, with 8in/8out ($800?) Even if you have a word clock input, you're going to have to synthesize that from the 10 MHz. Maybe it's easier to just make a S/PDIF which is a MUCH more common sync signal. ( I think S/PDIF is something like 3 MHz) The HPSDR folks also might have something... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
I use a Lynx One sound card, it has analog and digital I/O and MIDI I/O and clock I/O. Their manuals are available on line at www.lynxstudio.com. These are profession 24 bit cards, the analog I/O uses balanced interfaces. They handle AES/EBU and SP DIF digital audio formats. The sound card can take an internal clock, an external clock input on the MIDI port, there is a parallel clock header on the PC board, and a digital clock input on the digital audio lines. It can accept a 13.5 Mhz video dot clock, a 27 Mhz video dot clock, and a word clock and word clock/256. It can also take a single source frequency as a referenve clock. Its basicaly set up to sync and slave SMPTE timing systems Hope that helped.. Rex Moncur wrote: Hi all Does anyone have any experience of locking a USB external soundcard to a GPSDO 10 MHz reference. I am interested in advice on any good quality soundcards that can be readily locked to either 10 MHz or if necessary to some other frequency that we can derive from a GPSDO source. I have done some tests with the SignalLink soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz lock frequency. This requires some cutting of tracks to remove the internal oscillator feedback and insert the locking frequency. 12 MHz is readily derived from 10 MHz but I have not been able to get it to lock. The Texas instruments data sheet suggests that it is possible to use an external refernce but also says this is not recommended. With this expereicne I would rather find a sound card that is designed for external locking that does not require the cutting of tracks. For info the purpose of this request is that we are looking at using very narrow bandwidth modes at less than 1 mHz for light wave communcation. To date using LEDs and cloud reflection we have worked over 200 km with WSJT but we should be able to do 20 dB better if we can get down to milli-Hz bandwidths (at the expense of spending all night to complete a QSO). Our expereince to date is that standard sound cards are just not stable to better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS locking let us get down to sub milli-Hz levels. Rex VK7MO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards
Demian Martin skrev: Magnus Danielson wrote: The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Cheers, Magnus Without getting too audiophile there are several considerations. Toslink is bandwidth limited- the LED's are not really fast enough for 96K and really not for 192K sampling. The effect is high jitter on the link or a lost connection. The high jitter may not matter if the sampling is done with the external capture system (most of which are much more expensive). SPDIF or AES/EBU don't have the bandwidth limitation but can have other issues. I think you meant to say the electrical S/P-DIF and AES/EBU. The cheap ones don't have transformer isolation, however the transformers can increase the jitter on the link. Depends on the transformer. The AES-3 electical form of AES/EBU (balanced on XLR) has a drawback in that it may be hooked up over lines, patchfields and cross-connects not intended for AES/EBU signals. This can cause some grief. Installation standards has changed as a result as a consequence. For smaller systems may the transformer not be as much of an issue as in larger installations. The unbalanced form of AES/EBU, AES-3-id, is becomming popular. It should not be confused with S/P-DIF since it is distinct in several forms, except for the obvious difference in subcode content. You can use external USB capture, I'm playing with an EMU Tracker pre gadget that seems to do 192K at 24 bits pretty well and for $125. But I get better results from the ESI Juli@ pci card for around the same price, very low distortion and noise, and good Alsa support in Linux. It may be all that's needed. It is. Wordclock input? Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Maybe I lost track and missed something, but I don't think I ever saw more on the subject of specific high-end sound cards that might be useful for nutty measurements. From an earlier list message: [F]or best noise/jitter-performance an external ADC should be used, connected through a digital link to a PC sound card. One could do a lot worse than the TI PCM4222 eval board (http://focus.ti.com/docs/prod/folders/print/pcm4222.html), which accepts an external clock if so desired. At $149 (plus a tenner or two for the sound card) this will likely be much cheaper than an equivalent FireWire-device. The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. JDB. [using a custom board with a similar setup in a narrowband VNA] -- LART. 250 MIPS under one Watt. Free hardware design files. http://www.lartmaker.nl/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
J.D. Bakker skrev: Maybe I lost track and missed something, but I don't think I ever saw more on the subject of specific high-end sound cards that might be useful for nutty measurements. From an earlier list message: [F]or best noise/jitter-performance an external ADC should be used, connected through a digital link to a PC sound card. One could do a lot worse than the TI PCM4222 eval board (http://focus.ti.com/docs/prod/folders/print/pcm4222.html), which accepts an external clock if so desired. At $149 (plus a tenner or two for the sound card) this will likely be much cheaper than an equivalent FireWire-device. The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Magnus Danielson wrote: J.D. Bakker skrev: Maybe I lost track and missed something, but I don't think I ever saw more on the subject of specific high-end sound cards that might be useful for nutty measurements. From an earlier list message: [F]or best noise/jitter-performance an external ADC should be used, connected through a digital link to a PC sound card. One could do a lot worse than the TI PCM4222 eval board (http://focus.ti.com/docs/prod/folders/print/pcm4222.html), which accepts an external clock if so desired. At $149 (plus a tenner or two for the sound card) this will likely be much cheaper than an equivalent FireWire-device. The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Cheers, Magnus Hej Magnus Relatively high jitter being one problem. Limited sampling rate being another. If one has a cheap 16 bit sound card what will it do with 24 bit data from an external ADC? Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Consumer audio optical links (TOSlink) are 1000 micron (yes, it sounds better than 1mm) plastic fiber, which is fairly high loss (1000 dB/km), which is fine for 1-2 m cables. TOSlink is actually a trademark of Toshiba http://www.toshiba.com/taec/components/ProdLineGuide/toslink.pdf describes all. TOSlink has worked fine for me, except in one case, where the cable was flexed a lot, and it eventually developed cracks and the loss shot up. It should be relatively trouble free. The connector is a positive mate and keyed, and as long as you don't get debris in the hole in the chassis side, it should work fine. It's not a bad interface, although, I think not well suited to many mate/demate cycles (I don't know for sure, but the trusty 1/4 phone plug is a pretty rugged design). One data sheet I have says 500 mate/demate cycles. I was amused when the guy at the stereo store tried to sell me on RF shielded TOSlink cables, claiming it would provide more clarity and definition in the sound. Uh-huh.. Sort of like the green marking pen for the edges of your CDs to reduce internal reflections, etc. (I, of course, would only use the finest brush made from selected hairs of Tibetan mountain goats to apply a dye made from chlorophyll molecules selected using an electron microscope by trained technicians, etc.. A marking pen? My $14000 speaker cables supported on carefully oriented pure fused silica supports would wither in shame.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Lux, James P wrote: I was amused when the guy at the stereo store tried to sell me on RF shielded TOSlink cables, claiming it would provide more clarity and definition in the sound. Uh-huh.. Sort of like the green marking pen for the edges of your CDs to reduce internal reflections, etc. (I, of course, would only use the finest brush made from selected hairs of Tibetan mountain goats to apply a dye made from chlorophyll molecules selected using an electron microscope by trained technicians, etc.. A marking pen? My $14000 speaker cables supported on carefully oriented pure fused silica supports would wither in shame.) We have a rule here -- no discussion of audiophile insanity! You'll thank me in the end if we avoid a few hundred anecdotes about speaker cable and $500 knobs. :-) John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Cheers, Magnus Hej Magnus Relatively high jitter being one problem. Limited sampling rate being another. If one has a cheap 16 bit sound card what will it do with 24 bit data from an external ADC? I would imagine that the sound card is just being used as a digital bus interface, and the A/D won't feature into it. Kind of depends on whether the device driver for the sound card accepts anything on the S/PDIF or whether it assumes 16 bits. I think S/PDIF is 20bits/sample, but there's probably a 24 bit flavor. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
At 10:30 +1300 14-01-2009, Bruce Griffiths wrote: Magnus Danielson wrote: J.D. Bakker skrev: [F]or best noise/jitter-performance an external ADC should be used, connected through a digital link to a PC sound card.[...] The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup.[...] The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems.[...] Relatively high jitter being one problem. Limited sampling rate being another. Both true; IME practical limits are ~7m for 24bit/96ksps/stereo and ~3m for 24bit/192ksps/stereo, depending on TX and RX. My best experiences are with Toshiba TX/RX and pre-made cable listed as 'ADAT Lightpipe' rather than 'TOSLINK'. Both are the same on a mechanical level; the former is a pro audio de facto standard used to transfer multichannel audio around in studios, and its customers tend to be a bit more picky wrt out-of-spec cables. Jitter is not a problem as long as (a) the converter is the timing master and (b) the PC end doesn't try to do resampling or other 'clever' tricks (I know of no current mainstream chipsets that do). If one has a cheap 16 bit sound card what will it do with 24 bit data from an external ADC? It truncates it to its 16 MSBs. Note that you'll have a very hard time buying a new internal 16 bit sound card these days, never mind one with S/PDIF. The only 16 bit S/PDIF interfaces you could get are USB ones designed around TI's PCM29xx USB codecs (and not much else). As these top out at 48ksps, they are of limited use anyway. Many of the cheapest Home Theater PCI Sound Cards are built around the CMI8738 chip or one of its derivatives. This chip offers no-frills S/PDIF I/O up to 96ksps for a very low price, and as pretty much all boards that I have seen are a clone of the manufacturer's evaluation board, the S/PDIF signal is almost always easily available on a .1in pitch pin header (which may or may not be populated). I use it for quite a few test setups, but I do have a more expensive card (RME 9652) if I need more channels or a higher sampling rate. JDB. [disclaimer: the drivers are also an issue, naturally. I do most of my signal processing under Linux, which has good drivers for the CMI8738. On Windows and/or OSX YMMV, but I would be surprised if it did not work at all] -- LART. 250 MIPS under one Watt. Free hardware design files. http://www.lartmaker.nl/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
John Ackermann N8UR wrote: Lux, James P wrote: I was amused when the guy at the stereo store tried to sell me on RF shielded TOSlink cables, claiming it would provide more clarity and definition in the sound. Uh-huh.. Sort of like the green marking pen for the edges of your CDs to reduce internal reflections, etc. (I, of course, would only use the finest brush made from selected hairs of Tibetan mountain goats to apply a dye made from chlorophyll molecules selected using an electron microscope by trained technicians, etc.. A marking pen? My $14000 speaker cables supported on carefully oriented pure fused silica supports would wither in shame.) We have a rule here -- no discussion of audiophile insanity! You'll thank me in the end if we avoid a few hundred anecdotes about speaker cable and $500 knobs. :-) John Good, John. I was just about to suggest the same voluntary prohibition. -Rex ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Lux, James P skrev: optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Consumer audio optical links (TOSlink) are 1000 micron (yes, it sounds better than 1mm) plastic fiber, which is fairly high loss (1000 dB/km), which is fine for 1-2 m cables. TOSlink is actually a trademark of Toshiba http://www.toshiba.com/taec/components/ProdLineGuide/toslink.pdf describes all. TOSlink has worked fine for me, except in one case, where the cable was flexed a lot, and it eventually developed cracks and the loss shot up. Trouble is, many want some 10 m runs. The unbalanced one into a good cable should be able to do much longer runs. The Phono (aka RCA) connector isn't really suited to the task, but there is pretty good limits on the slopes, so it should be fine. Propper BNC with good cable handles 90m of HD-SDI signal so I don't think I am stretching my knowledge beyond unreasnoble limits here... :) Using 4,5 GHz BW cable for AES/EBU testing is kind of interesting... :) It should be relatively trouble free. The connector is a positive mate and keyed, and as long as you don't get debris in the hole in the chassis side, it should work fine. It's not a bad interface, although, I think not well suited to many mate/demate cycles (I don't know for sure, but the trusty 1/4 phone plug is a pretty rugged design). One data sheet I have says 500 mate/demate cycles. I was amused when the guy at the stereo store tried to sell me on RF shielded TOSlink cables, claiming it would provide more clarity and definition in the sound. Uh-huh.. Sort of like the green marking pen for the edges of your CDs to reduce internal reflections, etc. (I, of course, would only use the finest brush made from selected hairs of Tibetan mountain goats to apply a dye made from chlorophyll molecules selected using an electron microscope by trained technicians, etc.. A marking pen? My $14000 speaker cables supported on carefully oriented pure fused silica supports would wither in shame.) You must have gold-plated connectros for your TOSlink, you KNOW that. :) (Yes, those cables exists!) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, January 13, 2009 3:01 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound cards L Consumer audio optical links (TOSlink) are 1000 micron (yes, it sounds better than 1mm) plastic fiber, which is fairly high loss (1000 dB/km), which is fine for 1-2 m cables. TOSlink is actually a trademark of Toshiba http://www.toshiba.com/taec/components/ProdLineGuide/toslink.p df describes all. TOSlink has worked fine for me, except in one case, where the cable was flexed a lot, and it eventually developed cracks and the loss shot up. Trouble is, many want some 10 m runs. Exactly.. I was just down in the lab, and looked at the cables we have strung all over the place, and for us, a 2m cable is positively short. An awful lot of 5m and 10m cables just patching one thing to another (consider going from a connector on a piece of equipment in one 2m high rack to a connector in another 2m rack. There's 3-4 m just in going up and down, not to mention the meter or so across, if the racks happen to be side by side. There ARE fancier cables and connectors in the same family that have more range, but are still pretty cheap components. The galvanic isolation and EMI immunity IS attractive. But, a piece of RG-58 sized coax and BNC connectors is awfully common and convenient. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. It's been a while since I did any serious work with fibers. There are 2 limitations. One is signal to noise. You have to get enough light in the transmit end so that after attenuation there will be enough coming out for the receiver to be able to find the bits. Attenuatiion is linear with length with a constant for getting in and out of the fiber. Add some more for splices/connectors. The other is dispersion. If you have a multi-mode fiber, some of the photons bounce around more than others which results in a longer path and increased transit time. Simple geometry is a good approximation. The net result is that the photons get smeared in time. If your pulses are too narrow (bitrate too high), the smearing will cause adjacent bits to overlap and you can't easily sort things out at the receiver. Single mode fibers don't have modal dispersion. But they do have chromatic dispersion. Long distance telco links use very narrow bandwidth lasers. One characteristic of dispersion is that there is a trade-off between distance and bandwidth. Fibers have ratings in megabit-miles. Typical multi-mode fibers were 300-500 megabit-miles. Single mode fibers are roughly 7-9 microns dia for the active region. Multi-mode fibers were 50 or 62.5 microns. Roughly 10 years ago, there was a sweet spot at 155 megabits (OC-3) and 2 km using LEDs for the transmitter and multi-mode fibers. Since then, they are using low cost lasers (from CDs) so things have changed. If you wanted faster or farther, you used a laser and single mode fibers. The engineering/specsmanship on the overall link was super conservative. It was essentially impossible to measure the error rate. The trick is to insert enough attenuation so you get enough errors to measure, then compute what you would get without the attenuation. I haven't worked with plastic fibers. I'd expect the engineering to be conservative so it should just work. If it doesn't the obvious problems are dirt/mud at the connectors or cracked/broken fibers. (I'm assuming a sane length.) One disadvantage of conservative engineering is that a system that's broken might actually work well enough to act like a flaky system. I'm thinking of something like a broken fiber that is sometimes held in place close-enough by the jacket. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Spoil sport! Daun -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of John Ackermann N8UR Sent: Tuesday, January 13, 2009 4:51 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound cards Lux, James P wrote: I was amused when the guy at the stereo store tried to sell me on RF shielded TOSlink cables, claiming it would provide more clarity and definition in the sound. Uh-huh.. Sort of like the green marking pen for the edges of your CDs to reduce internal reflections, etc. (I, of course, would only use the finest brush made from selected hairs of Tibetan mountain goats to apply a dye made from chlorophyll molecules selected using an electron microscope by trained technicians, etc.. A marking pen? My $14000 speaker cables supported on carefully oriented pure fused silica supports would wither in shame.) We have a rule here -- no discussion of audiophile insanity! You'll thank me in the end if we avoid a few hundred anecdotes about speaker cable and $500 knobs. :-) John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards
Magnus Danielson wrote: The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Cheers, Magnus Without getting too audiophile there are several considerations. Toslink is bandwidth limited- the LED's are not really fast enough for 96K and really not for 192K sampling. The effect is high jitter on the link or a lost connection. The high jitter may not matter if the sampling is done with the external capture system (most of which are much more expensive). SPDIF or AES/EBU don't have the bandwidth limitation but can have other issues. The cheap ones don't have transformer isolation, however the transformers can increase the jitter on the link. You can use external USB capture, I'm playing with an EMU Tracker pre gadget that seems to do 192K at 24 bits pretty well and for $125. But I get better results from the ESI Juli@ pci card for around the same price, very low distortion and noise, and good Alsa support in Linux. It may be all that's needed. -Demian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Tuesday, January 13, 2009 3:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound cards I haven't worked with plastic fibers. I'd expect the engineering to be conservative so it should just work. If it doesn't the obvious problems are dirt/mud at the connectors or cracked/broken fibers. (I'm assuming a sane length.) One disadvantage of conservative engineering is that a system that's broken might actually work well enough to act like a flaky system. I'm thinking of something like a broken fiber that is sometimes held in place close-enough by the jacket. And, in a situation where the plastic fiber is just getting the databits from A/D into computer, as long as the BER is reasonably low, it works. You're not worried about actually using the fiber for accurate timing, just as a data transport. BTW, the scenario of broken fiber held by the jacket is very close to the one failure I've had with plastic fiber. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards
Firecomm.com has some nice parts to look at --- On Tue, 1/13/09, Demian Martin demi...@attglobal.net wrote: From: Demian Martin demi...@attglobal.net Subject: Re: [time-nuts] Sound Cards To: time-nuts@febo.com Date: Tuesday, January 13, 2009, 4:05 PM Magnus Danielson wrote: The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Cheers, Magnus Without getting too audiophile there are several considerations. Toslink is bandwidth limited- the LED's are not really fast enough for 96K and really not for 192K sampling. The effect is high jitter on the link or a lost connection. The high jitter may not matter if the sampling is done with the external capture system (most of which are much more expensive). SPDIF or AES/EBU don't have the bandwidth limitation but can have other issues. The cheap ones don't have transformer isolation, however the transformers can increase the jitter on the link. You can use external USB capture, I'm playing with an EMU Tracker pre gadget that seems to do 192K at 24 bits pretty well and for $125. But I get better results from the ESI Juli@ pci card for around the same price, very low distortion and noise, and good Alsa support in Linux. It may be all that's needed. -Demian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound Cards
Steve Do you mean?: http://www.firecom.com/ Bruce steve heidmann wrote: Firecomm.com has some nice parts to look at --- On Tue, 1/13/09, Demian Martin demi...@attglobal.net wrote: From: Demian Martin demi...@attglobal.net Subject: Re: [time-nuts] Sound Cards To: time-nuts@febo.com Date: Tuesday, January 13, 2009, 4:05 PM Magnus Danielson wrote: The digital link in question is S/PDIF; with the current popularity of Home Theater systems cheap cards with digital I/O have become quite prevalent. As an added bonus, S/PDIF can be run over both coaxial and optical media, the latter being attractive in further isolating PC noise from any measurement setup. And of course, a manufacturer's evaluation board is much better documented and more suited to measurement-specific mods than a random sound card. The optical link commonly being used for S/P-DIF is TosLink and it seems like it can be the cause of many problems. It seems like some care in doing the optical link setup is needed. I have never digged into why the optical links have that problem. I can only guess, but bad optical coupling seems reasonable. The multimode fiber seems to be leaving one or two things to ask for. Cheers, Magnus Without getting too audiophile there are several considerations. Toslink is bandwidth limited- the LED's are not really fast enough for 96K and really not for 192K sampling. The effect is high jitter on the link or a lost connection. The high jitter may not matter if the sampling is done with the external capture system (most of which are much more expensive). SPDIF or AES/EBU don't have the bandwidth limitation but can have other issues. The cheap ones don't have transformer isolation, however the transformers can increase the jitter on the link. You can use external USB capture, I'm playing with an EMU Tracker pre gadget that seems to do 192K at 24 bits pretty well and for $125. But I get better results from the ESI Juli@ pci card for around the same price, very low distortion and noise, and good Alsa support in Linux. It may be all that's needed. -Demian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
John Ackermann wrote: One very interesting possibility is the HPSDR (High Performance Software Defined Radio) boards called Ozy and Janus. I'm not aware of anyone using this system for TF work, but it has some interesting possibilities. I bought mine for tf work, but sadly I have not gotten to it: I just can't seem to get my 2.5 yo boy interested enough in the subject yet, although he is very adept at removing all the dust caps from my gear. :-) -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Sound cards
In the uber-thread Sub Pico Second Phase logger, this exchange took place on 12/16: Bruce Griffiths wrote: Joseph M Gwinn wrote: time-nuts-boun...@febo.com wrote on 12/15/2008 06:42:59 PM: I've also looked at the specs for several other high end sound cards. Quite a few only have single ended inputs. Maybe, I should document the various cards and highlight their shortcomings etc for this application. That would be very useful. I'll start on this shortly. Maybe I lost track and missed something, but I don't think I ever saw more on the subject of specific high-end sound cards that might be useful for nutty measurements. I'd be interested to hear what any of the group has to share about relative merits of current sound cards that can be interfaced for measurements like what was being discussed in that earlier thread. (And some before and since.) From my own point of view, I'd most like to hear about any that are external -- connected by USB or 1394, rather than an internal card. This makes it more portable and easier to move between different PC's. Bruce or anyone, got more to share? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Rex said the following on 01/09/2009 06:37 AM: Maybe I lost track and missed something, but I don't think I ever saw more on the subject of specific high-end sound cards that might be useful for nutty measurements. I'd be interested to hear what any of the group has to share about relative merits of current sound cards that can be interfaced for measurements like what was being discussed in that earlier thread. (And some before and since.) From my own point of view, I'd most like to hear about any that are external -- connected by USB or 1394, rather than an internal card. This makes it more portable and easier to move between different PC's. [Shameless Plug] One very interesting possibility is the HPSDR (High Performance Software Defined Radio) boards called Ozy and Janus. Together with a passive backplane called Atlas, they provide an extremely high performance ADC/DAC that supports sampling to 192k and output via USB. The system was designed for use as the interface between a PC and an SDR and special attention was paid to low noise and flat frequency response. I am not certain, but I *think* that the inputs are DC coupled. The two boards, assembled and tested, run about $320, with a discount for TAPR members. The backplane is a fairly simple kit (lots of connector pins to solder, but not much complexity) that sells for $28, also with a discount for TAPR members. Bare boards, but not kits, for Ozy and Janus are also available for the adventurous. I'm not aware of anyone using this system for TF work, but it has some interesting possibilities. [/Shameless Plug] John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
I've been using a Edirol FA-66, a firewire box with two balanced inputs plus four more unbalanced. I think it can handle 192ks/24bit on 4 channels. A lot of hams use it for software defined radios, but I just know it has better sound, especially the lows, for playing MP3s compared to most sound cards and iPods. Rex wrote: I'd be interested to hear what any of the group has to share about relative merits of current sound cards that can be interfaced for measurements like what was being discussed in that earlier thread. (And some before and since.) From my own point of view, I'd most like to hear about any that are external -- connected by USB or 1394, rather than an internal card. This makes it more portable and easier to move between different PC's. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Eric Williams wrote: I've been using a Edirol FA-66, a firewire box with two balanced inputs plus four more unbalanced. I think it can handle 192ks/24bit on 4 channels. A lot of hams use it for software defined radios, but I just know it has better sound, especially the lows, for playing MP3s compared to most sound cards and iPods. Rex wrote: I'd be interested to hear what any of the group has to share about relative merits of current sound cards that can be interfaced for measurements like what was being discussed in that earlier thread. (And some before and since.) From my own point of view, I'd most like to hear about any that are external -- connected by USB or 1394, rather than an internal card. This makes it more portable and easier to move between different PC's. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. Like many external Firewire sound boxes it has +48V phantom power available, which can be something of a hazard for this application unless all external preamps etc are designed to survive accidental application of +48V to their outputs. It also has a relatively low maximum input (+4dBu ~1.2Vrms) making it perhaps a little less robust than one with a Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
Rex wrote: In the uber-thread Sub Pico Second Phase logger, this exchange took place on 12/16: Bruce Griffiths wrote: Joseph M Gwinn wrote: time-nuts-boun...@febo.com wrote on 12/15/2008 06:42:59 PM: I've also looked at the specs for several other high end sound cards. Quite a few only have single ended inputs. Maybe, I should document the various cards and highlight their shortcomings etc for this application. That would be very useful. I'll start on this shortly. Maybe I lost track and missed something, but I don't think I ever saw more on the subject of specific high-end sound cards that might be useful for nutty measurements. I'd be interested to hear what any of the group has to share about relative merits of current sound cards that can be interfaced for measurements like what was being discussed in that earlier thread. (And some before and since.) From my own point of view, I'd most like to hear about any that are external -- connected by USB or 1394, rather than an internal card. This makes it more portable and easier to move between different PC's. Bruce or anyone, got more to share? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. I did start compiling info on sound cards and boxes that are suitable. However I have yet to find a suitable simple way of presenting it. A spreadsheet doesnt work that well. I'll look at this again. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sound cards
John John Ackermann N8UR wrote: Rex said the following on 01/09/2009 06:37 AM: Maybe I lost track and missed something, but I don't think I ever saw more on the subject of specific high-end sound cards that might be useful for nutty measurements. I'd be interested to hear what any of the group has to share about relative merits of current sound cards that can be interfaced for measurements like what was being discussed in that earlier thread. (And some before and since.) From my own point of view, I'd most like to hear about any that are external -- connected by USB or 1394, rather than an internal card. This makes it more portable and easier to move between different PC's. [Shameless Plug] One very interesting possibility is the HPSDR (High Performance Software Defined Radio) boards called Ozy and Janus. Together with a passive backplane called Atlas, they provide an extremely high performance ADC/DAC that supports sampling to 192k and output via USB. The system was designed for use as the interface between a PC and an SDR and special attention was paid to low noise and flat frequency response. I am not certain, but I *think* that the inputs are DC coupled. Not according to the circuit schematic. The input coupling is 10uF + 10K with a corresponding low frequency 3dB cutoff of 1.6Hz. Default inputs are single ended, balanced inputs are accessible via a pair of headers. Input full scale is that of the AKM5394 ADC chip (1.7Vrms nominal). There is a small dc offset between the differential inputs to the AKM5394 to eliminate an idle tone related spurious output. The two boards, assembled and tested, run about $320, with a discount for TAPR members. The backplane is a fairly simple kit (lots of connector pins to solder, but not much complexity) that sells for $28, also with a discount for TAPR members. Bare boards, but not kits, for Ozy and Janus are also available for the adventurous. I'm not aware of anyone using this system for TF work, but it has some interesting possibilities. [/Shameless Plug] John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
