Re: [Flexradio] Audiocards, USB, etc.
All RFE cards have a built in impulse generator that we plan to use for real time phase and amplitude correction. We can generate a 5ns pulse that it 1.5V peak to peak. N4HY is planning to add the software soon to compute the impulse response of the receiver and correct any imbalances in the frequency domain. This should give us dramatic improvement in image rejection and will eliminate the current adjusement. It will also be used to "train" a new impulse noise blanker that will do linear subtraction of noise pulses. Bob has already captured the real impulse and has done Matlab simulations to prove the concept. Stay tuned. Gerald K5SDR > -Original Message- > From: Jim Lux [mailto:[EMAIL PROTECTED] > Sent: Monday, September 26, 2005 10:06 PM > To: Pedlow, Lee; Gerald Youngblood; Tayloe Dan-P26412; Ahti Aintila; > FlexRadio@flex-radio.biz > Subject: RE: [Flexradio] Audiocards, USB, etc. > > > At 07:08 PM 9/26/2005, Pedlow, Lee wrote: > >While the aggregate effect of "A" weighting vs. unweighted might appear > >to be "only" 3dB, the power spectral density (PSD) difference is > >enormous! The whole point of the "apparent" 100 plus dB SNR on a > >delta-sigma device is a technique where the conversion noise is shifted > >out of band. That's why we can have cheap ADCs and DACs. > > > >In my professional life, I've found a great variation in DACs and sound > >cards regarding both phase response and out of band performance. > >Because the conversion noise is shifted up in frequency, there can be > >quite a bit of garbage above 20KHz and honestly, not many folks > >typically look there and the cards aren't usually spec'd outside of > >20-20KHz. > > > >If you are doing downstream processing (like driving the QSD mixer), a > >poor purchase decision can cause real problems with IMD, spurs, PM and a > >whole host of other thrills. It is very difficult to treat the DAC > >output for spurs close in to the upper passband edge without messing up > >the pass band. Filters with steep slopes like elliptics and Chebys have > >crummy phase response. > > > Conceivably (but not necessarily practically), one can compensate for the > odd phase characteristics in the digital processing. The practical > problems are: the characteristics of such filters tend to be extremely > sensitive to small component variations; you're looking at places > where the > attenuation is changing rapidly, so small changes in frequency have big > effects. Can't make a silk purse of a sow's ear, even with digital post > processing (and deconvolution). > > I've been doing research in this kind of thing over the past > couple years, > using pilot tones to do on-the-fly calibration. It's not trivial, > and it's > not easy, particularly in real time. > > > > > Ones that have a compromise between > >phase/magnitude response (bessel) require an unreasonable (read > >unmanufactureable) order to get the garbage out and are unrepeatable due > >to component sensitivity. Many designs have the poor stop band rejection > >after just a few octaves above the corner, > > particularly in elliptic (Cauer) filters with zeros.. they often > have a big > bounce after the null. I guess they're counting on "other components" to > roll off the higher stuff. > > > a big issue in trying to get > >rid of the broadband D-S modulation noise that is characteristic with > >these types of DACs. Add that to the need for close channel matching in > >gain/phase vs. frequency for reasonable I-Q performance, section > >interaction I read a magazine about all this once :) > > > >**Start Rant > > > >We have damn near had fistfights in the lab over DAC selection for our > >digital cable and satellite box designs for the very reasons mentioned > >above. We never did have any acceptable results with belt and > >suspenders band aids (filters) for DACs having phenomenal datasheet SNRs > >and noise floors that in actuality had really Sh***y OOB noise > >performance, but nobody bothered to look before we invested a fortune in > >moving a design to manufacture and issues started to pop up. The > >wunderkind couldn't explain it with their expensive AP analyzers using a > >Brick Wall input filter to evaluate a DAC - Duh! They're no longer in > >my employ here. I'll bet they're now at a PC sound card company, since > >they typically could give a hoot about audio fidelity. > > > >**End Rant > > > >Caveat Emptor! > Just like CPU benchmarks.. the best test is in your application. > All data > sheets lie, the real question is whether the lie is important to you. > > > > > > James Lux, P.E. > Spacecraft Radio Frequency Subsystems Group > Flight Communications Systems Section > Jet Propulsion Laboratory, Mail Stop 161-213 > 4800 Oak Grove Drive > Pasadena CA 91109 > tel: (818)354-2075 > fax: (818)393-6875 > > >
Re: [Flexradio] Audiocards, USB, etc.
At 07:08 PM 9/26/2005, Pedlow, Lee wrote: While the aggregate effect of "A" weighting vs. unweighted might appear to be "only" 3dB, the power spectral density (PSD) difference is enormous! The whole point of the "apparent" 100 plus dB SNR on a delta-sigma device is a technique where the conversion noise is shifted out of band. That's why we can have cheap ADCs and DACs. In my professional life, I've found a great variation in DACs and sound cards regarding both phase response and out of band performance. Because the conversion noise is shifted up in frequency, there can be quite a bit of garbage above 20KHz and honestly, not many folks typically look there and the cards aren't usually spec'd outside of 20-20KHz. If you are doing downstream processing (like driving the QSD mixer), a poor purchase decision can cause real problems with IMD, spurs, PM and a whole host of other thrills. It is very difficult to treat the DAC output for spurs close in to the upper passband edge without messing up the pass band. Filters with steep slopes like elliptics and Chebys have crummy phase response. Conceivably (but not necessarily practically), one can compensate for the odd phase characteristics in the digital processing. The practical problems are: the characteristics of such filters tend to be extremely sensitive to small component variations; you're looking at places where the attenuation is changing rapidly, so small changes in frequency have big effects. Can't make a silk purse of a sow's ear, even with digital post processing (and deconvolution). I've been doing research in this kind of thing over the past couple years, using pilot tones to do on-the-fly calibration. It's not trivial, and it's not easy, particularly in real time. Ones that have a compromise between phase/magnitude response (bessel) require an unreasonable (read unmanufactureable) order to get the garbage out and are unrepeatable due to component sensitivity. Many designs have the poor stop band rejection after just a few octaves above the corner, particularly in elliptic (Cauer) filters with zeros.. they often have a big bounce after the null. I guess they're counting on "other components" to roll off the higher stuff. a big issue in trying to get rid of the broadband D-S modulation noise that is characteristic with these types of DACs. Add that to the need for close channel matching in gain/phase vs. frequency for reasonable I-Q performance, section interaction I read a magazine about all this once :) **Start Rant We have damn near had fistfights in the lab over DAC selection for our digital cable and satellite box designs for the very reasons mentioned above. We never did have any acceptable results with belt and suspenders band aids (filters) for DACs having phenomenal datasheet SNRs and noise floors that in actuality had really Sh***y OOB noise performance, but nobody bothered to look before we invested a fortune in moving a design to manufacture and issues started to pop up. The wunderkind couldn't explain it with their expensive AP analyzers using a Brick Wall input filter to evaluate a DAC - Duh! They're no longer in my employ here. I'll bet they're now at a PC sound card company, since they typically could give a hoot about audio fidelity. **End Rant Caveat Emptor! Just like CPU benchmarks.. the best test is in your application. All data sheets lie, the real question is whether the lie is important to you. James Lux, P.E. Spacecraft Radio Frequency Subsystems Group Flight Communications Systems Section Jet Propulsion Laboratory, Mail Stop 161-213 4800 Oak Grove Drive Pasadena CA 91109 tel: (818)354-2075 fax: (818)393-6875
Re: [Flexradio] Audiocards, USB, etc.
While the aggregate effect of "A" weighting vs. unweighted might appear to be "only" 3dB, the power spectral density (PSD) difference is enormous! The whole point of the "apparent" 100 plus dB SNR on a delta-sigma device is a technique where the conversion noise is shifted out of band. That's why we can have cheap ADCs and DACs. In my professional life, I've found a great variation in DACs and sound cards regarding both phase response and out of band performance. Because the conversion noise is shifted up in frequency, there can be quite a bit of garbage above 20KHz and honestly, not many folks typically look there and the cards aren't usually spec'd outside of 20-20KHz. If you are doing downstream processing (like driving the QSD mixer), a poor purchase decision can cause real problems with IMD, spurs, PM and a whole host of other thrills. It is very difficult to treat the DAC output for spurs close in to the upper passband edge without messing up the pass band. Filters with steep slopes like elliptics and Chebys have crummy phase response. Ones that have a compromise between phase/magnitude response (bessel) require an unreasonable (read unmanufactureable) order to get the garbage out and are unrepeatable due to component sensitivity. Many designs have the poor stop band rejection after just a few octaves above the corner, a big issue in trying to get rid of the broadband D-S modulation noise that is characteristic with these types of DACs. Add that to the need for close channel matching in gain/phase vs. frequency for reasonable I-Q performance, section interaction I read a magazine about all this once :) **Start Rant We have damn near had fistfights in the lab over DAC selection for our digital cable and satellite box designs for the very reasons mentioned above. We never did have any acceptable results with belt and suspenders band aids (filters) for DACs having phenomenal datasheet SNRs and noise floors that in actuality had really Sh***y OOB noise performance, but nobody bothered to look before we invested a fortune in moving a design to manufacture and issues started to pop up. The wunderkind couldn't explain it with their expensive AP analyzers using a Brick Wall input filter to evaluate a DAC - Duh! They're no longer in my employ here. I'll bet they're now at a PC sound card company, since they typically could give a hoot about audio fidelity. **End Rant Caveat Emptor! Lee Pedlow Systems Engineering Sony Electronics, Inc. San Diego, CA CONFIDENTIAL This email is covered by the Electronic Communications Privacy Act, 18 U.S.C. 2510-2521 and is legally privileged. This e-mail is intended only for the personal and confidential use of the individual(s) to which it is addressed and may contain confidential information. If you are not the intended recipient, you are hereby notified that you have received this document in error, and that any review, distribution, copying or disclosure is not authorized. If you have received this communication in error, please notify the sender immediately by telephone and destroy the message. -Original Message- From: Gerald Youngblood [mailto:[EMAIL PROTECTED] Sent: Monday, September 26, 2005 3:02 PM To: Pedlow, Lee; Jim Lux; Tayloe Dan-P26412; Ahti Aintila; FlexRadio@flex-radio.biz Subject: RE: [Flexradio] Audiocards, USB, etc. Unweighted dynamic range is approximately 3dB below A weighted. Some converters specify both. Gerald K5SDR
Re: [Flexradio] Audiocards, USB, etc.
Unweighted dynamic range is approximately 3dB below A weighted. Some converters specify both. Gerald K5SDR > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Pedlow, Lee > Sent: Monday, September 26, 2005 2:31 PM > To: Jim Lux; Tayloe Dan-P26412; Ahti Aintila; FlexRadio@flex-radio.biz > Subject: Re: [Flexradio] Audiocards, USB, etc. > > > > The use of "A" weighting in A/D & D/A measurements is a bit of snake-oil > marketeering. It hides the HF artifacts present in delta-sigma > conversion. There is a big difference in specs for a given DS device > measured unweighted and "A" weighted. The philosophical argument is > that "A" weighting better approximated the MTF of the ear and therefore > carries significance because it will better represent the listener's > perceived performance. We have found that it also hides noise at the > very high end of the audio spectrum (and beyond - check that out too). > This HF garbage can play havoc in other parts of a processing chain. > When one looks at AF converters, one really needs to look at SNR, > floors, etc. out past the nyquist frequency (40KHz+) of the card in > question. > > It is quite difficult to maintain passband performance with analog > filtering downstream from the card to fix "close-in" noise due to slope > factor, especially on DACs. While one can easily Pspice a model, they > are difficult to physically realize or manufacture with any > repeatability. As a result, it is best to find cards, converters or > whatever that don't exhibit these issues and avoid comparison of devices > based upon the snake-oil specs. > > Lee Pedlow > Systems Engineering > Sony Electronics, Inc. > San Diego, CA > > > > > CONFIDENTIAL > > This email is covered by the Electronic Communications Privacy Act, 18 > U.S.C. 2510-2521 and is legally privileged. This e-mail is intended only > for the personal and confidential use of the individual(s) to which it > is addressed and may contain confidential information. If you are not > the intended recipient, you are hereby notified that you have received > this document in error, and that any review, distribution, copying or > disclosure is not authorized. If you have received this communication > in error, please notify the sender immediately by telephone and destroy > the message. > > > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jim Lux > Sent: Saturday, September 24, 2005 2:48 PM > To: Tayloe Dan-P26412; Ahti Aintila; FlexRadio@flex-radio.biz > Subject: Re: [Flexradio] Audiocards, USB, etc. > > At 02:24 PM 9/24/2005, Tayloe Dan-P26412 wrote: > >This 29v pk-pk sound card range is the essence of my concern about > >sound cards. The gain must not be constant. > > > > > >The TI part, as specified on page 7, has an input range of +/-2.5v, > >centered around 2.5v or 5v peak to peak. This is the maximum input > > > >Lets look at the Wolfson part. On page 6, the input rage of this part > >is specified to be 2v RMS which can also be expressed as +/-2.8v or > >5.6v pk-pk. This seems a bit odd because the part has a supply voltage > > >of only 5v, and I would not expect the input to be larger than the > >supply range. > > If there were a onchip voltage divider? > More likely, that spec has more to do with where some diode forward > biases. > > The A weighted vs. non-weighted difference is probably significant since > >we probably use these in an unweighted manner. Thus the TI part is > >probably really a 109 db dynamic range part. > > Almost certainly. I am curious as to why they use A weighting, which is > really for evaluating SPLs. > > > >Ideally, you should be able to get 6 db of range for every bit in the > A/D > >converter. Thus, it would seem that 24 bit A/D converters would be > capable > >of 144 db of dynamic range (there might be a n-1 factor in here, 138 > db, I do > >not remember). This is obviously not the case with real converters. I > have > >seen real converters approach this only when they are running very > slow, such > >as a 10 Hz sampling rate. Since we want 48+ KHz sampling rates, we get > less > >conversion accuracy and a smaller dynamic range. > > high performance converters usually have a ENOB number, which rolls all > the > errors into one number. ENOB is always < converter bits. > > > >The good news is that to the extent A/D converters improve (more > dynamic > >range), > >simply buying a better sound card should be all that is needed to > upgrade th
Re: [Flexradio] Audiocards, USB, etc.
To amplify Lee's point; for a very dramatic spectrum display of the HF noise, take a look at the demonstration that Alan K2WS did with his Audigy-2zs card! http://www.n9vv.com/K2WS.html (scroll down) Ken Pedlow, Lee wrote: The use of "A" weighting in A/D & D/A measurements is a bit of snake-oil marketeering. It hides the HF artifacts present in delta-sigma conversion. There is a big difference in specs for a given DS device
Re: [Flexradio] Audiocards, USB, etc.
The use of "A" weighting in A/D & D/A measurements is a bit of snake-oil marketeering. It hides the HF artifacts present in delta-sigma conversion. There is a big difference in specs for a given DS device measured unweighted and "A" weighted. The philosophical argument is that "A" weighting better approximated the MTF of the ear and therefore carries significance because it will better represent the listener's perceived performance. We have found that it also hides noise at the very high end of the audio spectrum (and beyond - check that out too). This HF garbage can play havoc in other parts of a processing chain. When one looks at AF converters, one really needs to look at SNR, floors, etc. out past the nyquist frequency (40KHz+) of the card in question. It is quite difficult to maintain passband performance with analog filtering downstream from the card to fix "close-in" noise due to slope factor, especially on DACs. While one can easily Pspice a model, they are difficult to physically realize or manufacture with any repeatability. As a result, it is best to find cards, converters or whatever that don't exhibit these issues and avoid comparison of devices based upon the snake-oil specs. Lee Pedlow Systems Engineering Sony Electronics, Inc. San Diego, CA CONFIDENTIAL This email is covered by the Electronic Communications Privacy Act, 18 U.S.C. 2510-2521 and is legally privileged. This e-mail is intended only for the personal and confidential use of the individual(s) to which it is addressed and may contain confidential information. If you are not the intended recipient, you are hereby notified that you have received this document in error, and that any review, distribution, copying or disclosure is not authorized. If you have received this communication in error, please notify the sender immediately by telephone and destroy the message. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Lux Sent: Saturday, September 24, 2005 2:48 PM To: Tayloe Dan-P26412; Ahti Aintila; FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. At 02:24 PM 9/24/2005, Tayloe Dan-P26412 wrote: >This 29v pk-pk sound card range is the essence of my concern about >sound cards. The gain must not be constant. > > >The TI part, as specified on page 7, has an input range of +/-2.5v, >centered around 2.5v or 5v peak to peak. This is the maximum input > >Lets look at the Wolfson part. On page 6, the input rage of this part >is specified to be 2v RMS which can also be expressed as +/-2.8v or >5.6v pk-pk. This seems a bit odd because the part has a supply voltage >of only 5v, and I would not expect the input to be larger than the >supply range. If there were a onchip voltage divider? More likely, that spec has more to do with where some diode forward biases. The A weighted vs. non-weighted difference is probably significant since >we probably use these in an unweighted manner. Thus the TI part is >probably really a 109 db dynamic range part. Almost certainly. I am curious as to why they use A weighting, which is really for evaluating SPLs. >Ideally, you should be able to get 6 db of range for every bit in the A/D >converter. Thus, it would seem that 24 bit A/D converters would be capable >of 144 db of dynamic range (there might be a n-1 factor in here, 138 db, I do >not remember). This is obviously not the case with real converters. I have >seen real converters approach this only when they are running very slow, such >as a 10 Hz sampling rate. Since we want 48+ KHz sampling rates, we get less >conversion accuracy and a smaller dynamic range. high performance converters usually have a ENOB number, which rolls all the errors into one number. ENOB is always < converter bits. >The good news is that to the extent A/D converters improve (more dynamic >range), >simply buying a better sound card should be all that is needed to upgrade the >performance of the receiver. Assuming that the A/D is actually the limiting factor. I suspect that things like nonlinearity in buffer amplifiers or in the mux/QSD, as well as reciprocal mixing of the LO phase noise will actually limit the performance. There's also the "total power" problem.. A wide open receiver gets the noise power for the entire band (even if much of it is filtered out after the downconversion), so a strong out of band signal far away can raise havoc still (or, at least require very high IP3 numbers for the system). If you were to just ballpark it and assume something like a 10dB NF for a 50MHz band, you're looking at -174 + 10 + 77 = -87 dBm input power, just for the noise. Add in some strong 60 and 120 Hz sources, etc, and a bit of selectivity in the front end starts to look like a good idea. It's remarkably
Re: [Flexradio] Audiocards, USB, etc.
Dan, You are failing to account for the bandwidth difference in the measurements. Blocking dynamic range in receivers is measured typically in 500Hz. Sound cards are typically measured in 20KHz, which puts your assumptions off by 16dB. Lynx sound cards will deliver around 117dB unweighted, which would put them at 133dB IN BAND blocking dynamic range. As I recall from memory, the Lynx cards will overdrive at around +24dBu or so. Once again, most users will agree that third order dynamic range is significantly more important than blocking dynamic range. You will hit third order limits on virtually all modern receivers before you hit blocking limits. 73, Gerald K5SDR > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Tayloe Dan-P26412 > Sent: Saturday, September 24, 2005 4:25 PM > To: Ahti Aintila; FlexRadio@flex-radio.biz > Subject: Re: [Flexradio] Audiocards, USB, etc. > > > This 29v pk-pk sound card range is the essence of my concern > about sound cards. The gain must not be constant. > > Sound cards use A/D converter. The two best audio A/D converts > I know of (and there may be others) are the Texas Instruments > PCM1084 and the Wolfson WM8785 or WM876. The links for the data > sheets can be found at: > > http://focus.ti.com/lit/ds/symlink/pcm1804.pdf > > http://www.wolfson.co.uk/products/digital_audio/adcs/WM8785/ > > A sound card can be no better than it's A/D converter. Both of > The above converters are very similar. > > The TI part, as specified on page 7, has an input range of +/-2.5v, > centered around 2.5v or 5v peak to peak. This is the maximum input > voltage to this ADC. Distortion + noise is rated at -101 db with an > input at 0.5 db. Thus, the noise floor is about -100 db. Since the > +/-2.5v input maximum is a level higher than a 0 db level, the dynamic > range of the A/D converter is specified on page 7 as being 112 db > (A weighted). > > Lets look at the Wolfson part. On page 6, the input rage of this part > is specified to be 2v RMS which can also be expressed as +/-2.8v or > 5.6v pk-pk. This seems a bit odd because the part has a supply voltage > of only 5v, and I would not expect the input to be larger than the > supply range. The distortion is -102 db (I am assuming this is > distortion > + noise), similar to the TI part, and the dynamic range is 111 db > A weighted > and 108 db non-weighted. > > The A weighted vs. non-weighted difference is probably significant since > we probably use these in an unweighted manner. Thus the TI part > is probably > really a 109 db dynamic range part. > > Ideally, you should be able to get 6 db of range for every bit in the A/D > converter. Thus, it would seem that 24 bit A/D converters would > be capable > of 144 db of dynamic range (there might be a n-1 factor in here, > 138 db, I do > not remember). This is obviously not the case with real > converters. I have > seen real converters approach this only when they are running > very slow, such > as a 10 Hz sampling rate. Since we want 48+ KHz sampling rates, > we get less > conversion accuracy and a smaller dynamic range. > > Thus, the range on either of these parts from the weak to the strongest > signal than can be handled is 108 to 109 db. Thus, it is not > possible for > this A/D converter to have a blocking dynamic range greater than 112 db. > Since the current SDR1000 implementation is a wide band receiver, meaning > the A/D converter has no hardware filtering protection from large signals > far away, the burden of receiver performance falls squarely on the A/D > converter. If the A/D converter has a smallest signal to largest signal > range of 108 to 112 db, then the receiver can do no better than > this. Thus > my comment on why it would be nice to have a sound card with 145 > db of dynamic > range. They do not exist because the very best A/D converters > that the sound > card uses can do no better than 108 to 109 db. > > A sound card is capable of reducing > its gain when it sees a signal of 29v pk-pk, and increasing it > gain when the > signal is much smaller. However, the dynamic range, the ability > to hear a weak > signal in the presence of a large signal, does not change. It > can be no better > than 108 to 109 db in a wide band receiver such as the SDR1000. > > If the detector is good for 5v peak to peak, and the A/D > converter is good > for +/-2.5v signals, the best large signal performance would be > to run with no > gain at all. The problem would be an MDS of only -100 dbm, as > the spec sheet > indicates. A gain of at least 40 db would be required to lower > the MDS down to -140 dbm. However, not matter what you do, the > A/D conv
Re: [Flexradio] Audiocards, USB, etc.
Dan, Professional audio cards do not use variable gain structures. The standard measurement for dynamic range on sound cards is to inject a signal that is 1dB below full scale to measure the signal to noise ratio within a standard bandwidth of 20KHz. The specifications are usually "A Weighted" for to compensate for normal hearing. To remove A Weighting, subtract 3dB. There are formulas for converting S/N to NF if you know the un weighted S/N and bandwidth. This can also be converted to an equivalent number of bits. The best sigma delta converters have ENOB in the 19-20 bit range in a 20KHz bandwidth. You have to remember that dynamic range of sound cards is rated in a 20KHz bandwidth. This means that the 500Hz dynamic range will be 16dB higher than that of the 20KHz specification. The best ADCs will achieve 117dB (120dB A Weighted). This puts you at 133dB IN BAND! That means that a signal could be only 500Hz away and still maintain the blocking range. On the other hand, most people agree that blocking dynamic range is not really that important as a figure of merit. IMD dynamic range will come into play at signal levels well below the blocking level. 73, Gerald K5SDR > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Tayloe Dan-P26412 > Sent: Friday, September 23, 2005 7:05 PM > To: Ahti Aintila; FlexRadio@flex-radio.biz > Subject: Re: [Flexradio] Audiocards, USB, etc. > > > You might not be getting a true measure simply > by checking sensitivity (noise floor) and clipping > (largest signal). I think this measurement would be > good only if the card is known not to change its > internal gain between these two measurements types. > > Do audio cards do this? Do they have built in > variable gain structures that automatically handle > input signal overload? > > If so, what is then needed is an audio blocking test where > a weakest detectable audio signal is injected, and a > large signal neighbor is injected to the point the weak > signal goes away (blocked). This test will truly show the > usable dynamic range of an audio card. We would like > to have this dynamic range very large, ideally 130 to 145 > db to match the blocking performance of other rigs (I think > not very practical), but we do want this as large as possible. > > - Dan, N7VE > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila > Sent: Friday, September 23, 2005 4:09 PM > To: FlexRadio@flex-radio.biz > Subject: Re: [Flexradio] Audiocards, USB, etc. > > Hi Riho and Bob, > > If I am not mistaken, the dynamic range of the loopback > measurement in this case may be limited by the DAC that happens > to have noise about -106 dBA. > Another limiting factor is the maximum signal before clipping. > > The important parameters for our SDR-1000 receivers are the noise > and clipping levels of the ADC. Almost all ADC's in higher class > audio cards with balanced input have reasonably low noise but the > clipping level may be too low. According to my measurements with > Waveterminal 192X the clipping level is +22 dBu and the noise at > 24 kHz bandwidth is less than -103 dBu. > The measurements have been made with carefully balanced input and > isolating audio transformers at the input and output connections. > Sorry, I don't have the A-weighing filter. > > Due to the home made signal generator and low noise > instrumentation amplifier I cannot guarantee the correctness of > my measurement values, but clearly the limitations seem to be on > the SDR-1000 hardware side. > > 73, Ahti OH2RZ > > - Original Message - > From: "rihob., es7aaz" <[EMAIL PROTECTED]> > To: > Sent: Friday, September 23, 2005 7:15 PM > Subject: Re: [Flexradio] Audiocards, USB, etc. > > > > Hi, > > > > Bob: > > Esi Juli unbalanced loopback @ 24-bit, 48 kHz mode: > > http://www.hot.ee/es7aaz/Juli.htm > > > > P.S. It was RMAA 5.4 when I did this measurement. > > > > Rgds, > > Riho, ES7AAZ. > > > > > ___ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > > ___ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > >
Re: [Flexradio] Audiocards, USB, etc.
Hello Lyle, Yes, my card is Waveterminal 192X from ESI (EGO Systems Inc.) http://www.esi-pro.com/contact.php It has the "native" ASIO 2.0 driver, too. Of course, the compatibility with SDR-1000 is not the best, but somehow I can manage with it. 73, Ahti OH2RZ - Original Message - From: "Lyle Johnson" <[EMAIL PROTECTED]> To: "Ahti Aintila" <[EMAIL PROTECTED]> Cc: "Tayloe Dan-P26412" <[EMAIL PROTECTED]>; Sent: Sunday, September 25, 2005 11:54 PM Subject: Re: [Flexradio] Audiocards, USB, etc. Hello Ahti! In my previous message the input signal specification should read: AKM (Asahi Kasei) recommends before the ADC (AK5394A) a balanced input buffer (NJM5534) that reduces the input signal from max ±12.7Vpp to ±2.4Vpp. Sorry for ignoring the + and - signs. Are you using a commercial soundcard that includes the AK5394A? If so, please tell me which one it is. 73, Lyle KK7P
Re: [Flexradio] Audiocards, USB, etc.
Hello Ahti! In my previous message the input signal specification should read: AKM (Asahi Kasei) recommends before the ADC (AK5394A) a balanced input buffer (NJM5534) that reduces the input signal from max ±12.7Vpp to ±2.4Vpp. Sorry for ignoring the + and - signs. Are you using a commercial soundcard that includes the AK5394A? If so, please tell me which one it is. 73, Lyle KK7P
Re: [Flexradio] Audiocards, USB, etc.
In my previous message the input signal specification should read: AKM (Asahi Kasei) recommends before the ADC (AK5394A) a balanced input buffer (NJM5534) that reduces the input signal from max ±12.7Vpp to ±2.4Vpp. Sorry for ignoring the + and - signs. Ahti OH2RZ - Original Message - From: "Ahti Aintila" <[EMAIL PROTECTED]> To: "Lyle Johnson" <[EMAIL PROTECTED]>; "Tayloe Dan-P26412" <[EMAIL PROTECTED]> Cc: Sent: Sunday, September 25, 2005 10:20 AM Subject: Re: [Flexradio] Audiocards, USB, etc.
Re: [Flexradio] Audiocards, USB, etc.
Lyle, Jim, Dan et al., You all make so good comments! This is a fun learning process! Dan said: "This 29v pk-pk sound card range is the essence of my concern about sound cards. The gain must not be constant." And here is AKM's explanation: "ALC (Automatic Level Control) Automatic Level Control (ALC) is found on many AKM CODECs and ADCs. The ALC is located between the analog mic preamp and the ADC and maintains the incoming signal at a constant level. AKM's ALC provides control of Level, Time, Step and Attenuation. Level is a threshold value above which the ALC is initiated. Time is the amount of time that a signal must spend above the threshold before ALC starts. Step allows you to instantaneously "step" the clipped value down by the Attenuation value or to wait until a zero-crossing point is reached prior to making ALC adjustments. Attenuation allows you to attenuate on a per-sample basis until the signal level is reduced below the Threshold." Interesting! I don't know how exactly ESI has implemented their Waveterminal 192X, but AKM (Asahi Kasei) recommends before the ADC (AK5394A) a balanced input buffer (NJM5534) that reduces the input signal from max 12.7Vpp to 2.4Vpp. With this circuit they promise DR= 120 dB, S/(N+D)= 105 dB. There really seems to be some potential for dynamic range improvement. Any GOOD sugestions? 73, Ahti OH2RZ - Original Message - From: "Lyle Johnson" <[EMAIL PROTECTED]> To: "Tayloe Dan-P26412" <[EMAIL PROTECTED]> Cc: "Ahti Aintila" <[EMAIL PROTECTED]>; ; "Lyle Johnson" <[EMAIL PROTECTED]> Sent: Sunday, September 25, 2005 6:40 AM Subject: Re: [Flexradio] Audiocards, USB, etc. Hello Dan! I forgot to say that your measurements show that your sound card shows a 114 db dynamic range which is 5 to 6 db better than the specs guarantee them to be. Looks like there is some margin in the A/D converter specs. Sounds like someone need to push TI and Wolfson for better ADCs! Look at TI's PCM4202, which beats the specs of the PCM1804 by 6 dB at a cost of another $3.00 and 75 mW. And AKM's AK5394A (www.akm.com) is spec'ed 5 dB better than TI's 4202 :-) But uses another 365 mW over the '4202 and pricing is hard to find... -Lyle KK7P
Re: [Flexradio] Audiocards, USB, etc.
Hello Dan! I forgot to say that your measurements show that your sound card shows a 114 db dynamic range which is 5 to 6 db better than the specs guarantee them to be. Looks like there is some margin in the A/D converter specs. Sounds like someone need to push TI and Wolfson for better ADCs! Look at TI's PCM4202, which beats the specs of the PCM1804 by 6 dB at a cost of another $3.00 and 75 mW. And AKM's AK5394A (www.akm.com) is spec'ed 5 dB better than TI's 4202 :-) But uses another 365 mW over the '4202 and pricing is hard to find... -Lyle KK7P
Re: [Flexradio] Audiocards, USB, etc.
At 02:45 PM 9/24/2005, Tayloe Dan-P26412 wrote: I forgot to say that your measurements show that your sound card shows a 114 db dynamic range which is 5 to 6 db better than the specs guarantee them to be. Looks like there is some margin in the A/D converter specs. Sounds like someone need to push TI and Wolfson for better ADCs! - Dan, N7VE I'm sure if you tell them you've got guaranteed sales of 100 million units a year, they'll get right on it. I think we're in that "niche market" category. There have been some interesting analyses of speed vs bits performance for A/Ds over the years, and it seems that there are a few "sweet spots" that accomodate pretty much all architectures. In order to make an alternate architecture attractive, you'd have to go many orders of magnitude better. Here's an example. You've been able to get fast A/Ds (>20 MSPS) in 12 bit accuracy for decades. (the AD9042 is a venerable example) This is low enough dynamic range that you need some selectivity in front of it. That is, you can use it at the IF, but you're not going to be able to hook an antenna up to the A/D input and build an all digital receiver. In order to do the latter, you need to have a lot more bits (like 20-24+), while keeping the same high sample rates. Going to 13 bits or 14 bits or 16 bits just isn't worth it, because you STILL won't have enough dynamic range to get rid of the first conversion or preselector, but you've got a MUCH more expensive A/D now. However, that same 12 bit accuracy has been getting faster (although not by a factor of 10...the 9042 is 41 MSPS, and I don't know that there are any 400 MSPS 12 bit A/Ds out there) The big change has been in improving the performance of those 12 bits:the 9042 is 10.5 ENOB, newer parts are better than 11, and the 9042 only achieves good performance at a limited range of sample rates, newer parts work at any sample rate. Most important to system designers is the reduction in the power consumption; that bipolar 9042 draws half a watt(!), and new CMOS versions draw a lot less. There's also a wider variety of packages and IC processes to choose from. Maybe you need some amount of radiation tolerance.. the bipolar 9042 is a rock, the CMOS parts are kind of soft. New SiGe or SoI parts might get you low power AND rad tolerance. In any case, we're sort of going to have to live with what ever the consumer market finds useful. Jim, W6RMK
Re: [Flexradio] Audiocards, USB, etc.
At 02:24 PM 9/24/2005, Tayloe Dan-P26412 wrote: This 29v pk-pk sound card range is the essence of my concern about sound cards. The gain must not be constant. The TI part, as specified on page 7, has an input range of +/-2.5v, centered around 2.5v or 5v peak to peak. This is the maximum input Lets look at the Wolfson part. On page 6, the input rage of this part is specified to be 2v RMS which can also be expressed as +/-2.8v or 5.6v pk-pk. This seems a bit odd because the part has a supply voltage of only 5v, and I would not expect the input to be larger than the supply range. If there were a onchip voltage divider? More likely, that spec has more to do with where some diode forward biases. The A weighted vs. non-weighted difference is probably significant since we probably use these in an unweighted manner. Thus the TI part is probably really a 109 db dynamic range part. Almost certainly. I am curious as to why they use A weighting, which is really for evaluating SPLs. Ideally, you should be able to get 6 db of range for every bit in the A/D converter. Thus, it would seem that 24 bit A/D converters would be capable of 144 db of dynamic range (there might be a n-1 factor in here, 138 db, I do not remember). This is obviously not the case with real converters. I have seen real converters approach this only when they are running very slow, such as a 10 Hz sampling rate. Since we want 48+ KHz sampling rates, we get less conversion accuracy and a smaller dynamic range. high performance converters usually have a ENOB number, which rolls all the errors into one number. ENOB is always < converter bits. The good news is that to the extent A/D converters improve (more dynamic range), simply buying a better sound card should be all that is needed to upgrade the performance of the receiver. Assuming that the A/D is actually the limiting factor. I suspect that things like nonlinearity in buffer amplifiers or in the mux/QSD, as well as reciprocal mixing of the LO phase noise will actually limit the performance. There's also the "total power" problem.. A wide open receiver gets the noise power for the entire band (even if much of it is filtered out after the downconversion), so a strong out of band signal far away can raise havoc still (or, at least require very high IP3 numbers for the system). If you were to just ballpark it and assume something like a 10dB NF for a 50MHz band, you're looking at -174 + 10 + 77 = -87 dBm input power, just for the noise. Add in some strong 60 and 120 Hz sources, etc, and a bit of selectivity in the front end starts to look like a good idea. It's remarkably easy to get microvolts or even millivolts of 60 Hz into a system. Digital clocks will also be a problem. 0.1 V of switching hash on the power line isn't a real big deal for digital logic, but you'd better have pretty darn good power supply noise rejection in the analog part of the system. - Dan, N7VE James Lux, P.E. Spacecraft Radio Frequency Subsystems Group Flight Communications Systems Section Jet Propulsion Laboratory, Mail Stop 161-213 4800 Oak Grove Drive Pasadena CA 91109 tel: (818)354-2075 fax: (818)393-6875
Re: [Flexradio] Audiocards, USB, etc.
I forgot to say that your measurements show that your sound card shows a 114 db dynamic range which is 5 to 6 db better than the specs guarantee them to be. Looks like there is some margin in the A/D converter specs. Sounds like someone need to push TI and Wolfson for better ADCs! - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila Sent: Saturday, September 24, 2005 7:47 AM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. Thank you Dan and Jim for the good comments. Sure I noticed how difficult it is to measure the sound cards without proper instruments. The clipping (or compression) levels are easy, but the noise in the present computer environment and with signals approaching the thermal noise levels are challenging. Instead of measuring the audio card only I decided to continue with the whole SDR-1000 system. I recorded 1) the noise floor (dBm/500 Hz) with audio card input cable input connected to the radio and the antenna connector terminated to 50 ohm and then 2) with a signal to radio until clipping or compression was indicated at the line-in connector of the radio or at the SDR-1000 own measurement systems. The results were: Preamp Setting HIGH, -140 dBm/500 Hz, -26 dBm, INA163 out 25 Vpp Preamp Setting MED, -130 dBm/500 Hz, -16 dBm, INA163 out 25 Vpp Preamp Setting LOW, -130 dBm/500 Hz, -13 dBm, INA168 out 4.8 Vpp (1.4 dB compressed) My conclusion is that the QSD can take about 4 Vpp until it starts to saturate and my sound card can take 29 Vpp, so the amplifier after the QSD could have 17 dB voltage gain for optimal results. The front end gain need to be adjusted accordingly. Dan mentioned:"... ideally 130 to 145 db to match the blocking performance of other rigs...". This should be our target and to achieve that we need audio cards handle signal from tens of nanovolts to tens of volts. I estimate, the accuracy of the above measurements is about 1 dB. The measurements were made with PowerSDR 1.4.5 console with unmodified RFE. These figures serve as the reference when comparing the results of the ECO-25 modifications. 73, Ahti OH2RZ - Original Message - From: "Jim Lux" <[EMAIL PROTECTED]> To: "Tayloe Dan-P26412" <[EMAIL PROTECTED]>; "Tayloe Dan-P26412" <[EMAIL PROTECTED]>; "Ahti Aintila" <[EMAIL PROTECTED]>; Sent: Saturday, September 24, 2005 6:20 AM Subject: Re: [Flexradio] Audiocards, USB, etc. > At 05:40 PM 9/23/2005, Tayloe Dan-P26412 wrote: >>I would think that on top of the audio blocking test we also want to >>run audio IP3 tests and audio IP2 dynamic range tests as well to make >>sure that the distortion characteristics are at least as good as the >>SDR1000 front end. >> >>- Dan, N7VE > > > Such tests would be useful, but are quite challenging to make for high > performance systems. You can take two general approaches: > 1) Obssessively account for all the error sources, use very clean sources, > etc. so you can truly know that what you've measured is just the unit > under test, and not quirks of the experimental setup. > > 2) Measure it in a "typical setup", in which case the performance will > certainly measure out worse, but at least it's representative of what > you'll really get. > > > Consider that if you're looking for 140 dB relative levels, you're looking > for signals of a 0.1 microvolt on a 1 volt signal. I've done DC > measurements to 6 digits, and it's, frankly, an ordeal. > > You'd also need sources that are that good, which is no easy matter, > especially if you want to cover the full frequency span of the device > (several decades). For instance, the SRS DS360 claims <-100dBc distortion > from 10mHz to 20 kHz. It's not too pricey at about $3000. > > > > ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Audiocards, USB, etc.
This 29v pk-pk sound card range is the essence of my concern about sound cards. The gain must not be constant. Sound cards use A/D converter. The two best audio A/D converts I know of (and there may be others) are the Texas Instruments PCM1084 and the Wolfson WM8785 or WM876. The links for the data sheets can be found at: http://focus.ti.com/lit/ds/symlink/pcm1804.pdf http://www.wolfson.co.uk/products/digital_audio/adcs/WM8785/ A sound card can be no better than it's A/D converter. Both of The above converters are very similar. The TI part, as specified on page 7, has an input range of +/-2.5v, centered around 2.5v or 5v peak to peak. This is the maximum input voltage to this ADC. Distortion + noise is rated at -101 db with an input at 0.5 db. Thus, the noise floor is about -100 db. Since the +/-2.5v input maximum is a level higher than a 0 db level, the dynamic range of the A/D converter is specified on page 7 as being 112 db (A weighted). Lets look at the Wolfson part. On page 6, the input rage of this part is specified to be 2v RMS which can also be expressed as +/-2.8v or 5.6v pk-pk. This seems a bit odd because the part has a supply voltage of only 5v, and I would not expect the input to be larger than the supply range. The distortion is -102 db (I am assuming this is distortion + noise), similar to the TI part, and the dynamic range is 111 db A weighted and 108 db non-weighted. The A weighted vs. non-weighted difference is probably significant since we probably use these in an unweighted manner. Thus the TI part is probably really a 109 db dynamic range part. Ideally, you should be able to get 6 db of range for every bit in the A/D converter. Thus, it would seem that 24 bit A/D converters would be capable of 144 db of dynamic range (there might be a n-1 factor in here, 138 db, I do not remember). This is obviously not the case with real converters. I have seen real converters approach this only when they are running very slow, such as a 10 Hz sampling rate. Since we want 48+ KHz sampling rates, we get less conversion accuracy and a smaller dynamic range. Thus, the range on either of these parts from the weak to the strongest signal than can be handled is 108 to 109 db. Thus, it is not possible for this A/D converter to have a blocking dynamic range greater than 112 db. Since the current SDR1000 implementation is a wide band receiver, meaning the A/D converter has no hardware filtering protection from large signals far away, the burden of receiver performance falls squarely on the A/D converter. If the A/D converter has a smallest signal to largest signal range of 108 to 112 db, then the receiver can do no better than this. Thus my comment on why it would be nice to have a sound card with 145 db of dynamic range. They do not exist because the very best A/D converters that the sound card uses can do no better than 108 to 109 db. A sound card is capable of reducing its gain when it sees a signal of 29v pk-pk, and increasing it gain when the signal is much smaller. However, the dynamic range, the ability to hear a weak signal in the presence of a large signal, does not change. It can be no better than 108 to 109 db in a wide band receiver such as the SDR1000. If the detector is good for 5v peak to peak, and the A/D converter is good for +/-2.5v signals, the best large signal performance would be to run with no gain at all. The problem would be an MDS of only -100 dbm, as the spec sheet indicates. A gain of at least 40 db would be required to lower the MDS down to -140 dbm. However, not matter what you do, the A/D converter still has only ~110 db of dynamic range. Thus, with an MDS of -140, I would expect blocking to occur with a signal any where with in +/- 100 KHz with a level of -30 dbm or more (110 db of dynamic range). Although I have found -140 dbm sensitivity to be useful on 20m on at least one occasion (I was comparing one of my homebrew DC rigs to a K2 capable of -136 dbm), I understand that the lower Bands get progressively more noisy. For example, I understand that 40m rarely has a noise floor of less than -116 dbm (500 Hz BW). Thus the SDR approach of applying variable gain is indeed useful, given the 110 db dynamic signal range the best A/D converters are capable of producing. The good news is that to the extent A/D converters improve (more dynamic range), simply buying a better sound card should be all that is needed to upgrade the performance of the receiver. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila Sent: Saturday, September 24, 2005 7:47 AM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. Thank you Dan and Jim for the good comments. Sure I noticed how difficult it is to measure the sound cards without proper instruments. The clipping (or compression) levels are easy, but the noise i
Re: [Flexradio] Audiocards, USB, etc.
Thank you Dan and Jim for the good comments. Sure I noticed how difficult it is to measure the sound cards without proper instruments. The clipping (or compression) levels are easy, but the noise in the present computer environment and with signals approaching the thermal noise levels are challenging. Instead of measuring the audio card only I decided to continue with the whole SDR-1000 system. I recorded 1) the noise floor (dBm/500 Hz) with audio card input cable input connected to the radio and the antenna connector terminated to 50 ohm and then 2) with a signal to radio until clipping or compression was indicated at the line-in connector of the radio or at the SDR-1000 own measurement systems. The results were: Preamp Setting HIGH, -140 dBm/500 Hz, -26 dBm, INA163 out 25 Vpp Preamp Setting MED, -130 dBm/500 Hz, -16 dBm, INA163 out 25 Vpp Preamp Setting LOW, -130 dBm/500 Hz, -13 dBm, INA168 out 4.8 Vpp (1.4 dB compressed) My conclusion is that the QSD can take about 4 Vpp until it starts to saturate and my sound card can take 29 Vpp, so the amplifier after the QSD could have 17 dB voltage gain for optimal results. The front end gain need to be adjusted accordingly. Dan mentioned:"... ideally 130 to 145 db to match the blocking performance of other rigs...". This should be our target and to achieve that we need audio cards handle signal from tens of nanovolts to tens of volts. I estimate, the accuracy of the above measurements is about 1 dB. The measurements were made with PowerSDR 1.4.5 console with unmodified RFE. These figures serve as the reference when comparing the results of the ECO-25 modifications. 73, Ahti OH2RZ - Original Message - From: "Jim Lux" <[EMAIL PROTECTED]> To: "Tayloe Dan-P26412" <[EMAIL PROTECTED]>; "Tayloe Dan-P26412" <[EMAIL PROTECTED]>; "Ahti Aintila" <[EMAIL PROTECTED]>; Sent: Saturday, September 24, 2005 6:20 AM Subject: Re: [Flexradio] Audiocards, USB, etc. At 05:40 PM 9/23/2005, Tayloe Dan-P26412 wrote: I would think that on top of the audio blocking test we also want to run audio IP3 tests and audio IP2 dynamic range tests as well to make sure that the distortion characteristics are at least as good as the SDR1000 front end. - Dan, N7VE Such tests would be useful, but are quite challenging to make for high performance systems. You can take two general approaches: 1) Obssessively account for all the error sources, use very clean sources, etc. so you can truly know that what you've measured is just the unit under test, and not quirks of the experimental setup. 2) Measure it in a "typical setup", in which case the performance will certainly measure out worse, but at least it's representative of what you'll really get. Consider that if you're looking for 140 dB relative levels, you're looking for signals of a 0.1 microvolt on a 1 volt signal. I've done DC measurements to 6 digits, and it's, frankly, an ordeal. You'd also need sources that are that good, which is no easy matter, especially if you want to cover the full frequency span of the device (several decades). For instance, the SRS DS360 claims <-100dBc distortion from 10mHz to 20 kHz. It's not too pricey at about $3000.
Re: [Flexradio] Audiocards, USB, etc.
At 05:40 PM 9/23/2005, Tayloe Dan-P26412 wrote: I would think that on top of the audio blocking test we also want to run audio IP3 tests and audio IP2 dynamic range tests as well to make sure that the distortion characteristics are at least as good as the SDR1000 front end. - Dan, N7VE Such tests would be useful, but are quite challenging to make for high performance systems. You can take two general approaches: 1) Obssessively account for all the error sources, use very clean sources, etc. so you can truly know that what you've measured is just the unit under test, and not quirks of the experimental setup. 2) Measure it in a "typical setup", in which case the performance will certainly measure out worse, but at least it's representative of what you'll really get. Consider that if you're looking for 140 dB relative levels, you're looking for signals of a 0.1 microvolt on a 1 volt signal. I've done DC measurements to 6 digits, and it's, frankly, an ordeal. You'd also need sources that are that good, which is no easy matter, especially if you want to cover the full frequency span of the device (several decades). For instance, the SRS DS360 claims <-100dBc distortion from 10mHz to 20 kHz. It's not too pricey at about $3000.
Re: [Flexradio] Audiocards, USB, etc.
At 05:05 PM 9/23/2005, Tayloe Dan-P26412 wrote: You might not be getting a true measure simply by checking sensitivity (noise floor) and clipping (largest signal). I think this measurement would be good only if the card is known not to change its internal gain between these two measurements types. Do audio cards do this? Do they have built in variable gain structures that automatically handle input signal overload? If so, what is then needed is an audio blocking test where a weakest detectable audio signal is injected, and a large signal neighbor is injected to the point the weak signal goes away (blocked). This test will truly show the usable dynamic range of an audio card. We would like to have this dynamic range very large, ideally 130 to 145 db to match the blocking performance of other rigs (I think not very practical), but we do want this as large as possible. In fact, this is the kind of testing done on high performance A/Ds. You really also need to quantify things like differential non-linearity, timing jitter, etc, as well. There's also tests that resemble two tone testing for amplifiers, except they use broader band signals with precision notches. James Lux, P.E. Spacecraft Radio Frequency Subsystems Group Flight Communications Systems Section Jet Propulsion Laboratory, Mail Stop 161-213 4800 Oak Grove Drive Pasadena CA 91109 tel: (818)354-2075 fax: (818)393-6875
Re: [Flexradio] Audiocards, USB, etc.
I would think that on top of the audio blocking test we also want to run audio IP3 tests and audio IP2 dynamic range tests as well to make sure that the distortion characteristics are at least as good as the SDR1000 front end. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tayloe Dan-P26412 Sent: Friday, September 23, 2005 5:05 PM To: Ahti Aintila; FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. You might not be getting a true measure simply by checking sensitivity (noise floor) and clipping (largest signal). I think this measurement would be good only if the card is known not to change its internal gain between these two measurements types. Do audio cards do this? Do they have built in variable gain structures that automatically handle input signal overload? If so, what is then needed is an audio blocking test where a weakest detectable audio signal is injected, and a large signal neighbor is injected to the point the weak signal goes away (blocked). This test will truly show the usable dynamic range of an audio card. We would like to have this dynamic range very large, ideally 130 to 145 db to match the blocking performance of other rigs (I think not very practical), but we do want this as large as possible. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila Sent: Friday, September 23, 2005 4:09 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. Hi Riho and Bob, If I am not mistaken, the dynamic range of the loopback measurement in this case may be limited by the DAC that happens to have noise about -106 dBA. Another limiting factor is the maximum signal before clipping. The important parameters for our SDR-1000 receivers are the noise and clipping levels of the ADC. Almost all ADC's in higher class audio cards with balanced input have reasonably low noise but the clipping level may be too low. According to my measurements with Waveterminal 192X the clipping level is +22 dBu and the noise at 24 kHz bandwidth is less than -103 dBu. The measurements have been made with carefully balanced input and isolating audio transformers at the input and output connections. Sorry, I don't have the A-weighing filter. Due to the home made signal generator and low noise instrumentation amplifier I cannot guarantee the correctness of my measurement values, but clearly the limitations seem to be on the SDR-1000 hardware side. 73, Ahti OH2RZ - Original Message - From: "rihob., es7aaz" <[EMAIL PROTECTED]> To: Sent: Friday, September 23, 2005 7:15 PM Subject: Re: [Flexradio] Audiocards, USB, etc. > Hi, > > Bob: > Esi Juli unbalanced loopback @ 24-bit, 48 kHz mode: > http://www.hot.ee/es7aaz/Juli.htm > > P.S. It was RMAA 5.4 when I did this measurement. > > Rgds, > Riho, ES7AAZ. > ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Audiocards, USB, etc.
You might not be getting a true measure simply by checking sensitivity (noise floor) and clipping (largest signal). I think this measurement would be good only if the card is known not to change its internal gain between these two measurements types. Do audio cards do this? Do they have built in variable gain structures that automatically handle input signal overload? If so, what is then needed is an audio blocking test where a weakest detectable audio signal is injected, and a large signal neighbor is injected to the point the weak signal goes away (blocked). This test will truly show the usable dynamic range of an audio card. We would like to have this dynamic range very large, ideally 130 to 145 db to match the blocking performance of other rigs (I think not very practical), but we do want this as large as possible. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila Sent: Friday, September 23, 2005 4:09 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. Hi Riho and Bob, If I am not mistaken, the dynamic range of the loopback measurement in this case may be limited by the DAC that happens to have noise about -106 dBA. Another limiting factor is the maximum signal before clipping. The important parameters for our SDR-1000 receivers are the noise and clipping levels of the ADC. Almost all ADC's in higher class audio cards with balanced input have reasonably low noise but the clipping level may be too low. According to my measurements with Waveterminal 192X the clipping level is +22 dBu and the noise at 24 kHz bandwidth is less than -103 dBu. The measurements have been made with carefully balanced input and isolating audio transformers at the input and output connections. Sorry, I don't have the A-weighing filter. Due to the home made signal generator and low noise instrumentation amplifier I cannot guarantee the correctness of my measurement values, but clearly the limitations seem to be on the SDR-1000 hardware side. 73, Ahti OH2RZ - Original Message - From: "rihob., es7aaz" <[EMAIL PROTECTED]> To: Sent: Friday, September 23, 2005 7:15 PM Subject: Re: [Flexradio] Audiocards, USB, etc. > Hi, > > Bob: > Esi Juli unbalanced loopback @ 24-bit, 48 kHz mode: > http://www.hot.ee/es7aaz/Juli.htm > > P.S. It was RMAA 5.4 when I did this measurement. > > Rgds, > Riho, ES7AAZ. > ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Audiocards, USB, etc.
Hi Riho and Bob, If I am not mistaken, the dynamic range of the loopback measurement in this case may be limited by the DAC that happens to have noise about -106 dBA. Another limiting factor is the maximum signal before clipping. The important parameters for our SDR-1000 receivers are the noise and clipping levels of the ADC. Almost all ADC's in higher class audio cards with balanced input have reasonably low noise but the clipping level may be too low. According to my measurements with Waveterminal 192X the clipping level is +22 dBu and the noise at 24 kHz bandwidth is less than -103 dBu. The measurements have been made with carefully balanced input and isolating audio transformers at the input and output connections. Sorry, I don't have the A-weighing filter. Due to the home made signal generator and low noise instrumentation amplifier I cannot guarantee the correctness of my measurement values, but clearly the limitations seem to be on the SDR-1000 hardware side. 73, Ahti OH2RZ - Original Message - From: "rihob., es7aaz" <[EMAIL PROTECTED]> To: Sent: Friday, September 23, 2005 7:15 PM Subject: Re: [Flexradio] Audiocards, USB, etc. Hi, Bob: Esi Juli unbalanced loopback @ 24-bit, 48 kHz mode: http://www.hot.ee/es7aaz/Juli.htm P.S. It was RMAA 5.4 when I did this measurement. Rgds, Riho, ES7AAZ.
Re: [Flexradio] Audiocards, USB, etc.
Riho: Muchas gracias! Spectacular. Only my Lynx L22 has measured better. 73 Bob rihob., es7aaz wrote: Hi, Bob: Esi Juli unbalanced loopback @ 24-bit, 48 kHz mode: http://www.hot.ee/es7aaz/Juli.htm P.S. It was RMAA 5.4 when I did this measurement. Rgds, Riho, ES7AAZ.
Re: [Flexradio] Audiocards, USB, etc.
Hi, Bob: Esi Juli unbalanced loopback @ 24-bit, 48 kHz mode: http://www.hot.ee/es7aaz/Juli.htm P.S. It was RMAA 5.4 when I did this measurement. Rgds, Riho, ES7AAZ. Robert W McGwier wrote: I sure do wish ESI/Audiotrak DirectWire 3.0 worked with other products. Please read the manufacturers specifications on these MAYA, ESI, Audiotrak cards, and in particular, please pay close attention to the noise floor specs. This is usually given in the "A/D SNR" or "A/D dynamic range" and is measured in dBA usually. The Delta 44, as specified on the M-Audio web site, measures 99 dBA. The Maya products, even their latest ones are 90 dBA. The Lynx L22 and the Audiophile 192 are well over 100 dBA but neither has sufficient inputs and outputs for our current working model. The ESI "Juli" that Riho likes has seriously good dynamic range if it meets their claims of 112 dB. It would be good if Riho could measure the loopback performance with RightMark Audio Analyzer (5.5 is now out) and let us know the results with this card. http://audio.rightmark.org/index_new.shtml For those who are just before giving up on a USB solution for your laptop, and will consider using 16 bit cards, the MAYA44 USB has better specs than the Extigy or the MP3+. Here is a block diagram of its workings: http://www.audiotrak.net/images/maya44usb_bd1.gif Its A/D SNR is 86 dBA and this is because of 18 bit parts. I have no experience with Maya, Audiotrak, etc. but the products look interesting and if they continue to improve the noise floor, we should get something reasonable from them. The Juli's specs look really good if they are hold up under measurement. It will be good for all soundcard program modes using the DirectWire 3.0 software. Bob N4HY ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Audiocards, USB, etc.
Regarding the higher end sound cards without enough inputs for use the SDR-1000 i.e. Audiophile 192. I've been following all the troubles, tribulations and comments regard dual sound card support in PowerSDR. However all those problems aside it would still seems to me that some kind of dual sound card support is a necessity for the future of the SDR-1000. So I'm wondering if the dual sound card problem could be effectively circumvented once the virtual sound card interface is implemented. I'm thinking in terms of handling the mic input in a completely separate stand alone app that would then interface to PowerSDR via the virtual sound card interface. Perhaps a new application written specifically for this purpose by someone from the Flex Radio software crew. Comments? Duane N9DG --- Robert W McGwier <[EMAIL PROTECTED]> wrote: > I sure do wish ESI/Audiotrak DirectWire 3.0 worked with > other products. > > Please read the manufacturers specifications on these MAYA, > ESI, > Audiotrak cards, and in particular, please pay close > attention to the > noise floor specs. This is usually given in the "A/D SNR" > or "A/D > dynamic range" and is measured in dBA usually. > > The Delta 44, as specified on the M-Audio web site, > measures 99 dBA. > The Maya products, even their latest ones are 90 dBA. The > Lynx L22 and > the Audiophile 192 are well over 100 dBA but neither has > sufficient > inputs and outputs for our current working model. The ESI > "Juli" that > Riho likes has seriously good dynamic range if it meets > their claims of > 112 dB. It would be good if Riho could measure the > loopback performance > with RightMark Audio Analyzer (5.5 is now out) and let us > know the > results with this card. > > http://audio.rightmark.org/index_new.shtml > > > For those who are just before giving up on a USB solution > for your > laptop, and will consider using 16 bit cards, the MAYA44 > USB has better > specs than the Extigy or the MP3+. > > Here is a block diagram of its workings: > > http://www.audiotrak.net/images/maya44usb_bd1.gif > > Its A/D SNR is 86 dBA and this is because of 18 bit parts. > > I have no experience with Maya, Audiotrak, etc. but the > products look > interesting and if they continue to improve the noise > floor, we should > get something reasonable from them. The Juli's specs look > really good > if they are hold up under measurement. It will be good > for all > soundcard program modes using the DirectWire 3.0 software. > > Bob > N4HY __ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com
[Flexradio] Audiocards, USB, etc.
I sure do wish ESI/Audiotrak DirectWire 3.0 worked with other products. Please read the manufacturers specifications on these MAYA, ESI, Audiotrak cards, and in particular, please pay close attention to the noise floor specs. This is usually given in the "A/D SNR" or "A/D dynamic range" and is measured in dBA usually. The Delta 44, as specified on the M-Audio web site, measures 99 dBA. The Maya products, even their latest ones are 90 dBA. The Lynx L22 and the Audiophile 192 are well over 100 dBA but neither has sufficient inputs and outputs for our current working model. The ESI "Juli" that Riho likes has seriously good dynamic range if it meets their claims of 112 dB. It would be good if Riho could measure the loopback performance with RightMark Audio Analyzer (5.5 is now out) and let us know the results with this card. http://audio.rightmark.org/index_new.shtml For those who are just before giving up on a USB solution for your laptop, and will consider using 16 bit cards, the MAYA44 USB has better specs than the Extigy or the MP3+. Here is a block diagram of its workings: http://www.audiotrak.net/images/maya44usb_bd1.gif Its A/D SNR is 86 dBA and this is because of 18 bit parts. I have no experience with Maya, Audiotrak, etc. but the products look interesting and if they continue to improve the noise floor, we should get something reasonable from them. The Juli's specs look really good if they are hold up under measurement. It will be good for all soundcard program modes using the DirectWire 3.0 software. Bob N4HY
