Re: [SlimDevices: Audiophiles] Transporter 3 word clock
Hello. THis is a really in-depth technical question. Proabably one of the original Slim designers would have to asnwer it. I've got my DAC going, and it uses the input Fs encoding in the input data stream to figure out what the output word clock F should be. If the Transporter is running off its internal clock, I see that the DAC is interpreting that correctly and tells me the input word rate. However, I designed my DAC with an output word clock so I could have the Transporter slave off the DAC's word clock. Here's the issue. When the Transporter is set to use its word clock, it appears that the Fs encoding is not coming from the source material like it should be. It looks like the Transporter is changing its mind about what the Fs value should be. giving first one encoding value, then another, then another, etc. I don't have a logic analyzer in there so I cant see what these encoding values are or how often they're changing. This behaviour is ONLY changing when there is a speed change associated with the two tracks. The upshot of the above is - when there is a speed change from one track to another, the DAC clock selection is oscillating, because the transporter keeps changing the darned Fs on it, the DAC reacts immediately to the change, giving a new clock speed, then it all goes round again. Again I can't really prove what is going on exactly because I haven't a LA at home :-(. Also - my DAC has the ability to manually generate the output word clock. When there is a conflict between the music file and the input word clock, the Transporter uses the word clock correctly. THat is, I can make it sound like the old tape decks that you could change the tape speed. I'm now going to see if the Fs is not correct when this happens. I think the Transporter MUST use the Fs encoding from source material, and ignore what the speed of the word clock is. Is there anyone at Logitech that can tell me what the Transporter is doing? That is, that Fs in the SPDIF output stream is a function of the word clock or not? I content it shouldn't be. If it is, that explains the oscillating behaviour when the Transporter is using its word clock input. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
I've seen now that whenever I change the word clock frequency, the Transporter is changing the Fs encoding to be all 0's (= 44.1 kHz code point) for a short period of time!! THis to me is an error and it's why there is a loop between the DAC and the Transporter. When the DAC is in auto frequency detect mode, it is using the Fs to generate the output word clock! THere is a loop now created becuase the Transporter isn't using the source file to determine what the Fs should be. Anybody at Logitech reading this? I wonder if maybe someone has worked thru this before and has a proposed fix. I've got a sizeable CPLD and I have a fair bit of latitude with what I do. It's a bit of a bummer if I have to forever change the word clock manually. I'd far prefer to have it in auto mode and do the switching on its own. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
My thinking is to have the Fs qualified by counting some number of same encodings and then changing word clock when that number is seen. Basically, I'm talking about an encoding debounce circuit. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;558021 Wrote: My thinking is to have the Fs qualified by counting some number of same encodings and then changing word clock when that number is seen. Basically, I'm talking about an encoding debounce circuit. Cool. It worked. What I did was stop changes to the oscillator output in the case of Fs = 44.1 kHz encoding until it's solid for 25 frames in a row. Now I can just leave the DAC in auto sense mode and the DAC is filtering out the spurious changes made by the Transporter. Programmable logic. Gotta love it. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;420007 Wrote: I'm not doing parallel DACs in my current design, although I am using the same DAC chips and fully balanced (2 chips per channel). I want to become successful with my first foray into this before I get really tricky and start laying down FPGAs and have to learn how to do digital filtering and cubic splines and such. Listened to the DAC today for the first time - running off my CD player. Now I better get going on the power supplies. And I guess I'd better buy a Tranporter now to test and listen to ! THe DAC is a home-grown one... I use a CPLD for input switching, clock switching, decoding the C-channel data and the like. Use a DIR9001 receiver, SRC4192, and dual PCM1704/K DAC chips per channel - I run full balanced. The analog portion is all discrete. Planes are split - 2 analog and 1 digital. And there are a dozen or maybe 15 regulators. I can't count them all !!! Here are my quick notes - it's my new DAC compared to a decade-old Classe CDP.3 CD player that also was the S/PDIF source for the DAC: --- First listen 7/22/09 ! The first impression is quite good. Its smooth, sounds a bit rolled off in the highs although the highs are definitely there and sound clearer and crisp but quieter. Its difficult to do critical listening with the fans of the power supplies going. Also AC units and TV in the other room. Output voltage is down maybe 2 or 3 dB compared to the Classe CDP.3 Ive had for many years. Maybe I can adjust it a bit higher. Compared to the Classe, it sounds more rounded, smooth, mellow. Also very detailed hear sounds Ive never heard before, and some sounds Im very familiar with sound quite a bit more clear less . Muddy perhaps. The thing is dead quiet, at full volume there is absolutely no sound coming from it whatsoever and its not even in a case and has wires hanging all over the place. The Classe sounds more etched, strident, or grainy in comparison and is definitely more noisy like hissing sound and ghosts of the music ie noise that is correlated to the signal and the DAC has none of that. Im really surprised at how different this DAC sounds from the Classe CD player. Also must keep in mind this thing is nearly new. It ran in for 6 or 8 hours on the bench today and I didnt give it any warm-up time at all before I started listening just powered it up and started to listen. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
There's a white paper describing the circuit in a bit more detail as well: http://www.wadia.com/technology/technicalpapers/ As I guessed, part of the reason they're doing it this way, is to give the DAC's more settling time. They're also claiming to get the full SNR benefit of a correlated signal, which I'm not sure I agree with. I'll have to think about that some more... FWIW, for your DAC design, adding DAC chips in parallel, and feeding them the same data, does result in an improvement in SNR, without the fancy delayed data. I recall at least one DAC design that used 32 chips in parallel! -- DCtoDaylight Audiophile wish list: Zero Distortion, Infinite Signal to Noise Ratio, and a Bandwidth from DC to Daylight DCtoDaylight's Profile: http://forums.slimdevices.com/member.php?userid=7284 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
DCtoDaylight;419925 Wrote: There's a white paper describing the circuit in a bit more detail as well: http://www.wadia.com/technology/technicalpapers/ As I guessed, part of the reason they're doing it this way, is to give the DAC's more settling time. They're also claiming to get the full SNR benefit of a correlated signal, which I'm not sure I agree with. I'll have to think about that some more... FWIW, for your DAC design, adding DAC chips in parallel, and feeding them the same data, does result in an improvement in SNR, without the fancy delayed data. I recall at least one DAC design that used 32 chips in parallel! THanks for the link. I'll give it a look. Wadia are correct - the signals do not have to be correlated in order to achieve the noise reduction they claim. I'm not doing parallel DACs in my current design, although I am using the same DAC chips and fully balanced (2 chips per channel). I want to become successful with my first foray into this before I get really tricky and start laying down FPGAs and have to learn how to do digital filtering and cubic splines and such. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
seanadams;419570 Wrote: In the normal source-DAC clock via s/pdif scheme yes, but here we are talking exclusively about a word clock scenario. Generally it's to not make you have to flip switches, but yes mixed sample rates within a playlist would require this. In that case it's still not ideal though, because the DAC is going to have to change the clock after the track has already begun (because it needs to get some data first). Depending on how fast it can change clocks this might not be a huge problem. Sean - now I get it. But, if the DAC is going to send its clock back to the transport at the correct rate (and playback of mixed rate sources is required), it's going to have to either read the status bit from the stream or recover the clock from the stream and then change its clock rate pretty quickly in either case? I wonder why the status bits were not used from day one? -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB3 (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Outdoors: Boom Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
Phil Leigh;419579 Wrote: Sean - now I get it. But, if the DAC is going to send its clock back to the transport at the correct rate (and playback of mixed rate sources is required), it's going to have to either read the status bit from the stream or recover the clock from the stream and then change its clock rate pretty quickly in either case? that's right. It's still a little hokey but much better than playing at the wrong rate. I wonder why the status bits were not used from day one? The status data can be used for a variety of things but I'm not sure specifically what the clock rate bits were intended for. Probably just for display purposes, since I don't think word-clocking was conceived until much later. Some s/pdif receiver chips will let you query both the channel status bits and the recovered clock rate as compared against a reference - they should always match. -- seanadams seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
seanadams;419572 Wrote: Huh? No you couldn't. The whole point of the DAC being in word clock mode is that the source is going to give you the bits at whatever rate the _DAC_ is running. Well, actually I'd consider it optimal to not deal with s/pdif and word clocking at all... this is what Transporter does by itself. I don't understand this at all. Driving the platter isn't the problem, and it doesn't work the way people might imagine from their experience with turntables or tapes. In a CD player, the clock drives the PCM output and this _pulls_ data from the platter via a buffer. The distinction being that the mechanical parts are NOT part of the timing path (as they are with analog media). So it's not nearly as bad as a lot of people think - jitter is nothing at all like wow/flutter - it happens on a time scale a billion times smaller. On the word clock not matching thing, I was thinking sample rate converter chip in-line. Then it doesn't matter too much if there's a mismatch - that was going to be the case anyhow if the word clock was not being used. So the thing about the 4 DACs is a patent owned by Wadia. It's in their 9xx series devices. What they teach is to have 4 DAC chips per differential half of a balanced signal - so that's 8 DAC chips per audio channel; a stereo pair has 16 DAC chips. The DAC chips are all connected at their current outputs, so the output current is 4x a single DAC chip and the I/V converter then has to take this into account - simple enough. Now the trick is that since there are 4 DAC chips in parallel, you don't fire off samples to all 4 of them at the same time, you fire off a sample to DAC0 at phase 0, then you fire off a sample to DAC1 at 90 degrees, etc. Of course you've already upsampled to at least a factor of 4 and dithered and.. to obtain 4 different output streams per channel. If you're really good I guess you even correlate the dither between + and - of a phase / channel so that the dithering is differentially rejected. Shoot, maybe that's a patent in its own right somewhere. Maybe Wadia has that one too. I'm just a hobbyist so I could make my own system like this and although strictly I'm not allowed to, the harm to the patent owner is nil - I'm not going to buy an audio system that expensive ever. Plus the barrier to entry is extremely high as one needs custom hardware (read: FPGAs) to duplicate something so complex. It would take hundreds of hours to duplicate the setup. (and guess who designs FPGAs for a living - :-) ) I don't know the patent number, if you search, you'll probably find it. Interesting stuff about the transport / clock source, I wondered if the output data was taken from a FIFO. So what the word clock to the Transporter is, is exactly the same thing except the DAC is external and the clock loop is a bit bigger. The key is, the jitter is held to nearly 0 and is not a function of S/PDIF or cables or the transport or (in this setup a $10 transport sounds the same as a $50,000 transport and anyone who tells you they can hear a difference is a liar - all the transport has to do is get the correct bits to the DAC; the DAC controls ALL of the jitter at the I output of the DAC chips). With a $2000 Transporter that delivers 96/24, I wouldn't want to be selling high end transports any more. I guess they'll always have a place, but I think in 20 years most of us will use our laptop with an external HDD to play our music from - well for the digital music anyhow. So Sean, please do tell if you can - what, if any, is the plan for a 192 kHz sample rate capable machine along the lines of the Transporter? Also - is there any plan for a real transport-only device that has no DACs inside? Probably very small market and it makes no sense for you to make such a beast but on the flip side, those with external DACS are paying a lot of cash for a lot of stuff they don't use. Cheers guys. I'm enjoying this. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
So the thing about the 4 DACs is a patent owned by Wadia. It's in their 9xx series devices. What they teach is to have 4 DAC chips per differential half of a balanced signal - so that's 8 DAC chips per audio channel; a stereo pair has 16 DAC chips. The DAC chips are all connected at their current outputs, so the output current is 4x a single DAC chip and the I/V converter then has to take this into account - simple enough. Now the trick is that since there are 4 DAC chips in parallel, you don't fire off samples to all 4 of them at the same time, you fire off a sample to DAC0 at phase 0, then you fire off a sample to DAC1 at 90 degrees, etc. Of course you've already upsampled to at least a factor of 4 and dithered and.. to obtain 4 different output streams per channel. If you're really good I guess you even correlate the dither between + and - of a phase / channel so that the dithering is differentially rejected. Shoot, maybe that's a patent in its own right somewhere. Maybe Wadia has that one too. impressively complicated! -- seanadams seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
DCtoDaylight;419811 Wrote: Ok, I understand now What they're doing is building a 4x oversampling unit, with a linear transfer function, in hardware, rather than in software. Seems like a slightly expensive way to implement it, although it would allow you to use slower DAC chips than doing the oversampling in the digital domain. You also get an improvement in the SNR, due to the DAC parallelization. Exactly - it is hardware oversampling and noise reduction also. Plus the added noise reduction of balanced in the analog portion. Also it's not linear. Its some sort of a non-linear curve fitter. I assume a cubic spline -ish math function. I imagine it sounds quite spectacular. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;419815 Wrote: Also it's not linear. Its some sort of a non-linear curve fitter. I assume a cubic spline -ish math function. Unless they feed each DAC with a totally different bit stream, then no, it will be linear. If they do feed each DAC with a different data, then you no longer get the SNR improvement gains of parallelization. The SNR improvement of parallelization comes as a result of the signal (ie data), from each DAC, being the same, while the noise is not. Thus the signals add, while the noise doesn't. If the signals are different, then the correlation goes down, and you don't gain the same benefits -- DCtoDaylight Audiophile wish list: Zero Distortion, Infinite Signal to Noise Ratio, and a Bandwidth from DC to Daylight DCtoDaylight's Profile: http://forums.slimdevices.com/member.php?userid=7284 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
seanadams;419281 Wrote: The other ones are 1000 = 88.2 1010 = 96 1110 = 192 (not supported by us) BTW this is a good tool to have if you're doing anything with s/pdif: http://www.nti-audio.com/Home/Products/Minstruments/DigilyzerDL1/tabid/82/Default.aspx Excellent, thanks. I'll see what I can do to add this function to my DAC. As you said, it's really the way to go that the DAC will use the correct word clock out based on the input S/PDIF signal. Wow - I'll have one up on the rest of the world (shouldn't last too long though). Cheers. W. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;419437 Wrote: Excellent, thanks. I'll see what I can do to add this function to my DAC. As you said, it's really the way to go that the DAC will use the correct word clock out based on the input S/PDIF signal. Wow - I'll have one up on the rest of the world (shouldn't last too long though). Cheers. W. ??? - you want to use the clock out from the DAC to drive the transport - you don't want to use the SPDIF clock -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB3 (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Outdoors: Boom Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
Phil Leigh;419438 Wrote: ??? - you want to use the clock out from the DAC to drive the transport - you don't want to use the SPDIF clock No, we're talking about using channel status bits (extra data embedded in the s/pdif stream) so that Transporter can communicate to the DAC what the correct clock frequency should be. These bits are already defined in the s/pdif spec, although I don't think anyone has used them for this purpose before. It would solve the problem of having to manually set front panel switches on the DAC to set the clock rate. -- seanadams seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
seanadams;419451 Wrote: No, we're talking about using channel status bits (extra data embedded in the s/pdif stream) so that Transporter can communicate to the DAC what the correct clock frequency should be. These bits are already defined in the s/pdif spec, although I don't think anyone has used them for this purpose before. It would solve the problem of having to manually set front panel switches on the DAC to set the clock rate. ah. hmmm... But don't dacs auto-detect the clock frequency from the recovered spdif clock? Is this about supporting a mixture of sample rate files? -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB3 (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Outdoors: Boom Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
Phil Leigh;419513 Wrote: ah. hmmm... But don't dacs auto-detect the clock frequency from the recovered spdif clock? Is this about supporting a mixture of sample rate files? I expose the DAC could detect the clock F, but why not do it as intended with the encoding in the bitstream - it's a LOT easier. Think what the way you suggest is - a reference with a counter and error bounds and two oscillators talking to each other and and and. What I will do is read the speed encoding from the S/PDIF, and use that to power up one oscillator that will generate 96 or 48 kHz, or power up another oscillator that will generate 88.2 or 44.1 kHz. The oscillator will drive the word clock out and the read side of the digital filter and the DAC chips. This is the IDEAL method to clock a DAC, and in fact the entire audio chain now has only a few ps of jitter in the one place it matters- the DAC chip inputs. If one was going to build the best audio music system they possibly could, what Sean has advised, and what I am building, is the way one would go about doing it. About the only thing I'm missing is paralleling, say, 4 DAC chips and offsetting time samples to the DACs by 90 degrees. THat's for another day and involves more work. Having the source clock driving the CD platter is in fact the worst possible way to make a digital music system and it is the most common method. Why? Simple - its the cheapest. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;419527 Wrote: About the only thing I'm missing is paralleling, say, 4 DAC chips and offsetting time samples to the DACs by 90 degrees. Care to elaborate on this idea? I'm trying to understand the advantage of doing this, and I'm drawing a complete blank on why you would want to offset anything by 90 degrees... -- DCtoDaylight Audiophile wish list: Zero Distortion, Infinite Signal to Noise Ratio, and a Bandwidth from DC to Daylight DCtoDaylight's Profile: http://forums.slimdevices.com/member.php?userid=7284 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
Phil Leigh;419513 Wrote: ah. hmmm... But don't dacs auto-detect the clock frequency from the recovered spdif clock? In the normal source-DAC clock via s/pdif scheme yes, but here we are talking exclusively about a word clock scenario. Is this about supporting a mixture of sample rate files? Generally it's to not make you have to flip switches, but yes mixed sample rates within a playlist would require this. In that case it's still not ideal though, because the DAC is going to have to change the clock after the track has already begun (because it needs to get some data first). Depending on how fast it can change clocks this might not be a huge problem. -- seanadams seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;419527 Wrote: I expose the DAC could detect the clock F, but why not do it as intended with the encoding in the bitstream - it's a LOT easier. Huh? No you couldn't. The whole point of the DAC being in word clock mode is that the source is going to give you the bits at whatever rate the _DAC_ is running. If one was going to build the best audio music system they possibly could, what Sean has advised, and what I am building, is the way one would go about doing it. Well, actually I'd consider it optimal to not deal with s/pdif and word clocking at all... this is what Transporter does by itself. About the only thing I'm missing is paralleling, say, 4 DAC chips and offsetting time samples to the DACs by 90 degrees. THat's for another day and involves more work. I don't understand this at all. Having the source clock driving the CD platter is in fact the worst possible way to make a digital music system and it is the most common method. Why? Simple - its the cheapest. Driving the platter isn't the problem, and it doesn't work the way people might imagine from their experience with turntables or tapes. In a CD player, the clock drives the PCM output and this _pulls_ data from the platter via a buffer. The distinction being that the mechanical parts are NOT part of the timing path (as they are with analog media). So it's not nearly as bad as a lot of people think - jitter is nothing at all like wow/flutter - it happens on a time scale a billion times smaller. -- seanadams seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
seanadams;418536 Wrote: If your DAC is smart enough to decipher the incoming S/PDIF channel status, you could set the outgoing clock accordingly as TP will indicate the correct playback frequency in those bits. I'm not aware of any DACs that actually do this - AFAIK they all require you to set manual toggle switches which I think is pretty hokey. Hi Sean, I'm having difficulty figuring out exactly what the code is I have to look for in order to automagically have my DAC switch the clock frequency. All I can find for S/PDIF is sample rate encodings in channel status byte 3, bits: 3210 = 44.1 kHz 0010 = 48 kHz 0011 = 32 kHz THere doesn't seem to be encodings for 88.2 kHz or 96 kHz. Does the Transporter write encodings other than the ones listed above and if so, what are they? I hope I've found the correct place to be looking for these encodings. Thanks much, W. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
The other ones are 1000 = 88.2 1010 = 96 1110 = 192 (not supported by us) BTW this is a good tool to have if you're doing anything with s/pdif: http://www.nti-audio.com/Home/Products/Minstruments/DigilyzerDL1/tabid/82/Default.aspx -- seanadams seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
Sean, THanks for the reply. Wow I was not expecting the Founder of the company to answer a question. We have had similar experiences as I was one of a handful of people who began a startup together in 2002 and that company was later purchased (alas, for a song). I am satisfied to see people who take a risk, build a Comapny that makes a REAL PRODUCT and employs people in meaningful work, see the fruits of their labor. My DAC will have a PIC on the board so perhaps I'll try to do as you suggest and have the clock switch using the channel status information. It's more than I was intending to take on but what the heck. I don't have to do it all at once. I'm adding some strategically placed resistors so the DAC can work statically while I work on SW - after getting the base HW to work. The DAC will have dual 1704K chips per channel (I have an all balanced system) and I've got separate L/R analog supplies, multiple regulated, and isolated from the digital so I hope it will turn out well. I think I'm doing most things that are in a high-end DAC. I was planning to test the Transporter lock to DAC by triggering off the source word clock, then as you say on scope channel B view the S/PDIF in and should see that they are locked. No worries. Dave, my apologies and thanks for the info. For some reason I didn't think of using Google to search, I searched the message board and read a frightful number of posts by people who appear to have no earthly clue what jitter is, spread their knowledge around. As always, on the net, you have to filter things. Cheers guys and wish me luck. -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;418425 Wrote: Fourth, for those who have a T3 alrady and are playing 96/24 files, is there a significant difference between those and CD ripped files? (I would think so). Along hese lines I downloaded the sampler 96/24 files from HDtracks and played thru my Duet. I thought it was quite dynamic compared to CD. Note that the Duet cannot play 96 kHz, I read that the PC SW downconverts the 96 kHz sample rate to 48 kHz, and sends that to the Duet. Cheers, and thanks Hmmm. I did a lousy job of writing this. What I meant was - if one compares: 1) CD ripped to file and play over transporter to good external DAC 2) that same source material that was mastered at 96/24 and played back over Transporter on the same DAC (obviously DAC is 44.1 / 96 capable) (eg (1) CD of Rebecca Pidgeon's The Raven ripped vs (2) the same album as 96/24 flac downloaded from HDtunes and both played thru Transporter - external DAC) Are people finding the 96/24 version significantly better sonically? Doesn't #2 sound a bunch better? -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
[SlimDevices: Audiophiles] Transporter 3 word clock
Hi all, I'm building my own DAC and I want to perhaps use a Transporter 3 as one of the inputs for purchased music and I want also to rip my CD collection so I can get rid of that large cabinet beside my stereo So... a few questions. I guess these are directed at Logitech technical types or hobbyists who have already been where I am and have done what I'm doing. If you don't KNOW the answer to the question, please keep your OPINION to yourself. I'm spending significant time designing and building a project and I don't want to have errors designed in. Yes I have searched but did not find answers to these questions. Firstly, what is the layer 0 protocol of the word clock input? That is, what is the voltage / impedance / duty cycle spec for this input? I see it's a BNC connector but I don't know if it's 50 ohms or 75 ohms and I've never been able to find a post on this board that says what the voltage or duty cycle are. Secondly, it appears that the input rates accepted are 44.1, 48, and 96 kHz. What does the Transporter do if faced with 96 kHz word clock input and a flacsource file that is from a ripped CD Does it convert the input data source (interpolating) to get the data rate to 96 kHz? Thirdly, does the Transporter 3 automatically detect the presence of the word clock and then use that as a source to lock its PLL to? Or would I have to go into some setting menu in SW to tell the Transporter to use the word clock or not ? Fourth, for those who have a T3 alrady and are playing 96/24 files, is there a significant difference between those and CD ripped files? (I would think so). Along hese lines I downloaded the sampler 96/24 files from HDtracks and played thru my Duet. I thought it was quite dynamic compared to CD. Note that the Duet cannot play 96 kHz, I read that the PC SW downconverts the 96 kHz sample rate to 48 kHz, and sends that to the Duet. Cheers, and thanks -- wayne325 wayne325's Profile: http://forums.slimdevices.com/member.php?userid=29916 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
wayne325;418425 Wrote: Hi all, I'm building my own DAC and I want to perhaps use a Transporter 3 as one of the inputs for purchased music and I want also to rip my CD collection so I can get rid of that large cabinet beside my stereo So... a few questions. I guess these are directed at Logitech technical types or hobbyists who have already been where I am and have done what I'm doing. If you don't KNOW the answer to the question, please keep your OPINION to yourself. I'm spending significant time designing and building a project and I don't want to have errors designed in. Yes I have searched but did not find answers to these questions. Firstly, what is the layer 0 protocol of the word clock input? That is, what is the voltage / impedance / duty cycle spec for this input? I see it's a BNC connector but I don't know if it's 50 ohms or 75 ohms and I've never been able to find a post on this board that says what the voltage or duty cycle are. Secondly, it appears that the input rates accepted are 44.1, 48, and 96 kHz. What does the Transporter do if faced with 96 kHz word clock input and a flacsource file that is from a ripped CD Does it convert the input data source (interpolating) to get the data rate to 96 kHz? Thirdly, does the Transporter 3 automatically detect the presence of the word clock and then use that as a source to lock its PLL to? Or would I have to go into some setting menu in SW to tell the Transporter to use the word clock or not ? Fourth, for those who have a T3 alrady and are playing 96/24 files, is there a significant difference between those and CD ripped files? (I would think so). Along hese lines I downloaded the sampler 96/24 files from HDtracks and played thru my Duet. I thought it was quite dynamic compared to CD. Note that the Duet cannot play 96 kHz, I read that the PC SW downconverts the 96 kHz sample rate to 48 kHz, and sends that to the Duet. Cheers, and thanks 1) The word clock is a standard word clock input. IF that doesn't answer your question you are already in trouble :-) 2) Don't know, but the whole idea is that the DAC clock drives the TP. Therefore, a 44.1 kHz rip will NOT be upsampled to anything else. 3) You need to set the TP to use the external clock input 4) No -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB3 (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Outdoors: Boom Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
Funny, I googled, and found Sean's earlier forum reply as the second match The word clock input will accept a signal up to 100Khz of at least 1V amplitude. It will accept practically any input but a 3V, 44.1KHz square wave is typical. The word clock is just that, a clock. The system relies on you setting it to the correct frequency. If you try an play back a 44.1k CD with the word clock running at 96k, your song will play back at 2.18x speed. Good luck! Dave -- DCtoDaylight Audiophile wish list: Zero Distortion, Infinite Signal to Noise Ratio, and a Bandwidth from DC to Daylight DCtoDaylight's Profile: http://forums.slimdevices.com/member.php?userid=7284 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Transporter 3 word clock
An ideal word clock source would be simply a 3.3 or 5V logic signal with a 100 ohm resistor in series. The impedance doesn't matter, that's just to protect you from a short. You could also put a ferrite in series to slow the edge, since a sharp transition is not needed or desirable here. You should test it with a function generator to get an idea how it works - and you can make fun sounds using the sweep knobs! What Transporter does with this signal is multiply it up to the required internal MCLK. Then all other clocks (LRCK, BICK) are derived from that MCLK, the same as they would be from an internally generated MCLK. It is really a dumb slave to whatever clock you give it. If your DAC is smart enough to decipher the incoming S/PDIF channel status, you could set the outgoing clock accordingly as TP will indicate the correct playback frequency in those bits. I'm not aware of any DACs that actually do this - AFAIK they all require you to set manual toggle switches which I think is pretty hokey. Once you have something hooked up, try putting a scope on 1) Transporter's MCLK and 2) your internal oscillator. They should be synchronized, with some arbitrary but constant phase offset. PS there is no TP3. There's TP and SB3. See: http://wiki.slimdevices.com/index.php/HardwareComparison -- seanadams seanadams's Profile: http://forums.slimdevices.com/member.php?userid=3 View this thread: http://forums.slimdevices.com/showthread.php?t=62747 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
