Audiophile USB to PCM

I have an excellent upsampler and dac (dCS Purcell/Delius) and am looking for the very best USB to PCM conversion. So far, I've tried SlimDevices Squeezebox, and Xitel Pro Hi-Fi link.

Both are very good, but I was wondering if there are any other options I should be considering. Both the Sutherland USB Preamp and the Wavelength USB Dac convert to analog. I'd like something of similar quality that stops short of the digital to analog conversion so that I can let the dCS gear do that.

Any suggestions would be appreciated.

I read about the Sutherland and it was panned as basically an expensive piece of junk (looks pretty cool though). If you can run a digital out from any external soundcard into your DAC, you would already be way beyond the Sutherland.
A professional caliber soundcard w/ AES/EBU output should out perform consumer oriented USB devices. I use an RME, but there are others.
The ESI U24 that we sell as part of our Professional test kit is 24 bit 96kHz and has SPDIF out as well as analog out. Might work very well for what you are trying to do.
What about something as simple as the Edirol UA-1D? Its a simple USB device with a single S/PDIF coax output. I use mine off my Win XP Pro box, going into a Theta Pro Basic IIIa. Works reliably for my set up, which is playing mp3s through the home office stereo. Hard to go wrong for $80.

I'm curious about the RME and other AES/EBU cards, however. Onhwy61, have you compared any of those to any of the simple USB devices like the Edirol or M-Audio Sonica?
Edesilva, I have two computer based systems. One uses the RME with the AES/EBU balanced digital out and the other an M-Audio Sonica with an optical out. The RME sounds better. The RME also betters the built in optical output on the Apple G5. It's not an earth shaking, dramatic, blows away type of difference, but it's there and I find it worthwhile.
Any other recommendations for a laptop??

There are various firewire based interfaces (Metric Halo, M-Audio and others), but I don't have direct experience with them. They tend to be geared to professional multi channel use. I've also seen PMCIA based interfaces.

Doesn't the dCS have a firewire option?
I use an Apogee USB Mini-Dac with my Mac G4 laptop -- sounds really good for casual listening, using the laptop as a juke box. I rip my CD's to the hard drive uncompressed using AIFF. I had an M-Audio Audiophile USB Dac prior to the Apogee -- the Apogee blows it away. Of course the M-Audio cost $175 while the Apogee cost $976.

Do you use the Apogee to convert to analog?? I'm just looking to convert from USB to PCM so I can run it into my dCS gear.


Yes, dCS has a firewire version but I don't have it.

I'm using an M audio Firewire Audiophile. It sounds quite good, but it has some quirky volume problems. They are supposed to address this in a future firmware upgrade, but until they do that, I can not recommend it.
Yes, I'm using the Mini-Dac as a DAC. I'm running USB from the Mac G4 laptop to the Apogee, then balanced XLR interconnects to a pair of Mackie HR824's --- I'm pretty astounded at the quality. I don't know that you need to convert the digital signal from your laptop to PCM in order to run it with your dCS gear. I could be wrong, but I believe you just need to keep it in digital since your dCS gear probably doesn't have a USB input, you need something between your laptop and dCS, something to connect them while keeping the signal in digital. I tried that with an input of a Proceed AVP2 so I could use the DAC in the Proceed. For some reason, it didn't sound that good. Only thing I can figure is that something in the M-Audio piece was degrading the signal somehow. Everything sounded time smeared. I'm going to guess that you could use the Apogee similarly and it would sound way better. I know the Apogee has a better clock/buffer which helps eliminate jitter, so maybe the signal was getting smeared by going through the M-Audio piece even though I didn't use it for DA conversion. When I get some time, I will experiment with the Apogee, connecting to the laptop with USB and taking an SPDiF out of the Apogee to the digital input of the Proceed and see if there's a huge improvement, as I expect, over the M-Audio piece. There may be a less expensive piece that will handle the transer and keep the signal in digital while eliminating jitter and smear for less money -- if there is, I'd like to know about it. In the meantime, I can tell you that the Apogee sounds great in my application.
Here is something that will take a USB input from your computer and convert it to toslink or SPDiF without performing DA conversion for $79 ----
Oops -- forget that one -- didn't notice that it is the opposite of what I thought. It is for sending digital input INTO your computer using the USB port. Sorry 'bout that. That's what I get for posting before I've had coffee!
No problemo Rsbeck!!! Edirol DOES make one that converts usb to pcm. As does M-audio, Xitel, Waveterminal, and several others. I'm just trying to find which one is the best.

Why do you want to convert to PCM before your DAC?
I want to use my audiophile grade DAC. It accepts a 16/44.1 signal....which I thought was PCM. Doesn't a CD player put out PCM. I thought I needed to convert the USB signal to PCM for it to be able to be accepted by the DAC. Is this incorrect?
Hbrandt, the music files stored on your hard drive are a PCM data stream which is can then be transmitted via the USB protocol to an external device. You simply want a device that connects to your computer with an USB cable and connects to your D/A with a Toslink, S/DIF or AES/EBU cable. It's a very minor point, but I believe it's incorrect to refer to the USB connection as converting the PCM data stream.
Harry, you are trying to do what I do, and the PCM conversion is necessary. I'm using an Edirol UA-1D right now, which has a USB dongle on one end and a connector for coax PCM out on the other. Nothing else, no DAC. Sounds good for background music running into my Theta (I'm using mp3s compressed with -alt preset extreme, not uncompressed AIFF/WAV/AAC). I believe the Edirol is limited to 16/44.1. Since USB is an asynch protocol, I believe there should be no USB induced jitter in such a setup. Not sure what RSBeck's set up was with the M-Audio, but I previously used a Sonica from M-Audio to do USB to PCM conversion (the version I had was not equipped with a DAC) and it sounded fine.
Technically, I believe you are correct. The files on the hard drive are PCM, but they must be converted to a stream that can be read by a dac. I believe that there is a header that is stripped from the stream...and then, is simply a pcm bitstream. It is not a conversion per se...and I shouldn't have referred to it as such.

Bottom line is that I want to get tunes from my laptop to my sound system. I'll leave the specific terminology to the computer gurus.

I decided to go with the Waveterminal U24. My understanding is that it is very well made and will provide a bit accurate stream with no conversion from 44.1 to 48k. I'll report here what I find.

Thanks to all for your kind help.

Here's the Edirol piece to which Ed is referring. This is the reverse of the piece I posted before, which means it is what I thought the other piece was. It will take a USB connection from your computer and convert it to SPDiF or Toslink, keeping the signal in digital. But, nowhere does it say it converts the signal to PCM. I'm not sure where this is coming from. My understanding is that the computer puts the signal out in digital at whatever resolution you imported it and I don't know that it needs to be "converted" to PCM nor do I see that the Edirol piece performs this function. I'm not sure what the problem with the M-Audio piece wasm either -- but -- I can tell you that when I was running MP3, the pieces in my system were not critical. I could take a feed from the headphone out, split the signal into L & R, feed it into analogue inputs in my pre-amp and you couldn't tell much difference. Now that I import my CD's uncompressed, you can tell large differences between, for example, the M-Audio piece and the Apogee.
The Waveterminal piece is interesting. It offers sample rate conversion. Maybe this is what is needed to take the signal from the computer to a home audio DAC and maybe that is what was missing from the M-Audio piece. Like Harry, I am no computer expert, I learn as much as I can in order to get the computer to do what I need, but my interest lies far more in music, which is the carrot that leads me to learn about computers. I am curious to find a product that will let me connect the computer to the digital input on my pre-amp so I can use the DAC in the Proceed, so I will be interested in hearing about Harry's experience with the Waveterminal piece. I the meantime, I am getting a real kick out of this G4, Apogee, Mackie system I've built. It is surprisingly accurate, musical, and enjoyable. But, this has opened up a little mystery and now I am curious to know whether uncompressed music files like AIFF need to be converted before they can be read by a home audio DAC and why my Apogee DAC doesn't need any conversion before it can perform its magic.

Thanks!! Do you think any or these converters are better or worse than each other?? There are lots of them; M-Audio, Edirol, Xitel, Apogee, Ego Systems, etc.

Also, I'm interested in the differences between streaming through a network as the SlimDevices Squeezebox does, and the hardwired devices listed above. I guess the real issue is what is going to provide the most bit accurate stream most effectively.

Going back to basics, there is a bitstream on the CD and the idea is to feed that to a DAC to convert it to analog. PCM just (I believe) means pulse code modulation, which basically means communicating bits between two devices by an agreed upon standard for interpreting voltage pulses on the wire between them. USB is a serial interface, which means among other things (I think) that its buffered, so its a bit more hardware to implement than something translating pulses into TTL signals for digital processing. So, because coax digital is PCM, and USB is specific serial protocol, there is a conversion from a serial protocol to a different electrical format. Hopefully doesn't mean that the actual datastream of 1's and 0's is changing, but when I've got a box that is USB on one side and coax digital on the other, I call that a "converter."

Of course, I could be dead wrong. Its happened before. ; )

AIFF/WAV/MP3 is just a means for storing the bitstream on media. There is all sorts of stuff added to store things--directory records, sector sequence data, etc--even if you aren't doing any compression. But, with compression, you also need software to recover the original bitstream (or something that looks pretty close, if it was lossy compression).

I wonder, based on what you said, whether your M-Audio somehow ran the bitstream through a low end DAC and, if you used the digital out, ran it through an analog to digital converter. Doesn't seem to make much sense to me, but might explain the problems.

Sample rate conversion sounds sketchy to me in terms of rewards... Can't get more samples per second out than there are samples per second in. But, that is what oversampling is and that seems well beyond my technical competence. How does the thing *sound*? I guess the benefits of creating a 24/96 stream out of a 16/44 stream is going to depend heavily on the quality of what is doing the conversion...
Its actually "Eric," not "Ed." I should probably stick a response in that "where does your userID come from" thread. Every time I buy or sell something on A'gon, I get an email addressed to "Ed." *sigh*
Eric -- thanks for the info. Maybe it is even worse -- maybe the M-Audio converted the signal from digital to analogue and back to digital. Whatever it was, the Apogee sounds way better, but I know the Proceed has good DAC's, so I am pretty certain something went wrong inside the M-Audio piece. At some point, I am going to take an SPDiF out of the Apogee into the Proceed to compare them in that capacity.
As I understand, the major advantage of USB connection is ability to take your SPDIF interface as far as possible from the computer that generates plenty of RFI and other noises. USB, being buffered solution isn't likely to introduce jitter, but you'll need a box (where jitter will inevitably appear) that accepts USB data flow, and converts it to SPDIF, i.e. performs quality reclocking, etc. Here, if this box is treated just as part of the audio system, and connected with short good SPDIF cable to the DAC, there should be less jitter then from a normal CD player. However, for low jitter this box must have audiophile-grade power supply, oscillator, and other parts, so its price level must be expected somewhere near any other audiophile DAC. Cheap solutions must introduce lots of jitter, making the whole idea nonsense.
This thread has been very useful. My thanks to Eric, Dmitrydr, Rsbeck, and Ultraviolet, and onhwy61!! I actually understand quite a bit (no pun intended!!) more now than I did before. The signal coming through the USB port is 1's and 0's just like PCM. As I understand it, however, the signal needs to be modified, NOT converted to the same format as the signal coming out of a source like a CD player. The USB protocol is different and the conversion devices we are discussing remove some sort of header on the signal. Most are felt to be bit accurate.

My problem with the Xitel is that its cheap chipset converts 44.1 to 48k and based in what I've heard and read I have some concern that this adding artifact above the noise floor.

While the Waveterminal can do sample rate conversion between 32k, 44.1k, and 48k, this feature is unnessary and will not be utilized. Sample rate conversion is not what I want here.

My Waveterminal U24 is arriving today. I'll be able to report on the sonics of it later. Hopefully, I will have found the holy grail of connecting my Powerbook G4 to my audiophile system!!!

Looking forward to your report.
Wow....the Waveterminal U24 is spectacular. Just plugged it in and my Genesis Lens immediately read 44.1 khz. The sonics are outstanding. Hopefully tomorrow I'll be able to do some a/b comparisons with the Xitel. initial impression is that there is more detail, but there may a placebo effect since I just set it up!!!
The U24 is really great. It is a professional piece of equipment and I have not used it for music reporduction--only for state of the art measurements. I was looking forward to your report as well and I'm glad it turned out to be favorable. Now I might have to set up a music server system based on one of these for our house!!

You rock the house!!! What a great recommendation that really worked for me. Please excuse me for not buying it from you!!! i just might pick myself up a Parc and Parc Plus and unload my 3 TacT RCS 2.0s units that I use for total room correction of all channels in my home theater. I think your company and product is VERY impressive and heard great sound with the Parc at CES and HE 2004.

I've been doing a/b comparisons this evening between my Wadia 270se and my computer through the Waveterminal U24. The Wadia is definitely better but not by much. I never expected computer sound would be this outstanding!!!

Did you ever get your computer connected to your dCS DAC?

The dCS gear is doing upsampling and d/a conversion. My current path is:

Powerbook G4 (iTunes) via USB to Waveterminal U24 --> Genesis Digital Lens --> Apogee Big Ben --> TacT RCS 2.0s DD --> Apogee Big Ben --> dCS Purcell upsampler -> dCS Delius DAC.

Sounds great,
That's an interesting path to say the least. I count three jitter/clock solutions, a pre-amp, a USB to SPDiF converter, and an upsampler, before another upsampler and DAC. You sure you need all of that?

Yeah...well that's the question. Let me explain so that you don't think I'm a goofball!!! The Digital Lens has been there for a long time and has a nifty remote and allows me to use lots of digital inputs. I've done extensive a/b analysis and it is not causing any deterioration, although I don't think it's really helping a whole lot. The Apogee Big Ben is, in my view, the most progressive reclocking device to come along in years. it basically reclocks the incoming signal using an ultrastable clocking mechanism. It added tremendous improvement to my system. The signal then hits the TacT RCS 2.0s which I am using solely for room correction. Can't live without that either. But the output from the RCS needs to be reclocked again for optimal dejittering. But the Apogee doesn't do it's off to the dCS Purcell for upsampling to 24/176 (which I prefer to 24/192. Now the signal heads to the dCS Delius for conversion to Analog. I set the TacT and dCS gear to unity gain, because I don't like to use digital equipment for volume control....because volume attenuation leads to reduction of bits and resolution. To the analog signal heads to a Placette dual mono with its superb analog vishay resistor volume control. I know you think this all sounds a bit extreme and weird......but trust works!!!!

>>trust works!!!!<<

I trust you. Most of what we do in an effort to get better sound could be considered extreme and weird. Who am I to judge?

Thanks for the nonjudgmental attitude, man!!! I guess I'm a little defensive 'cause i've added all that gear and interconnects.

Just heard that the company making Waveterminal U24 is bought by Emagic. They also seem to have similar device, called Emagic Multichannel Interface A62m., with description as follows: "Versatile and practical - with 6 audio inputs and 2 audio outputs, MIDI I/O and USB hub, the A62 m offers mobility and quality in one compact interface. This makes it the ideal multi-purpose interface for use on the road or in your personal studio setup."

Any info/opinion on that?

Glad to hear it worked well. I guess I better try doing some audiophile stuff with it as well. I've been thinking about doing a WAV, non compressed music server with this as the D/A. Sounds like it would be really good. As to buying it elsewhere--no big deal. As I said it's a piece of test gear primarily bought by our dealers in their test kits. It's not a significant part of our business. Now as to getting rid of those TacTs and upgrading to the PARC--well now that's truly music to my ears:)


I have my all my channels balanced out with the TacT gear. Is the Parc plus avaliable yet?

The PARC + is available. The PARC + is slightly--but only slightly backlogged at this point. We are shipping, and catching up on demand. We should be in good shape within only a few weeks (I hope--if people would quit ordering them it would be a lot easier to catch up).
Even though I was an early adopter of TacT.......I'd have to commend you on the Parc. i think it is one of the all around best components to come out in a while. I basically don't let my TacT do anything above 300 Hz. I use it simply to knock out bass modes in my difficult room. And I also don't let it boost anything.....only cut. If the Parc had been around when I got into TacT...i may well have ended up with Parc. And it wouldn't surprise me if there is a Parc and Parc + in my future. I've followed the Parc at CES and HE 2004 and am VERY IMPRESSED.
Is there a way to bypass the waveterminal piece? Does the Edirol UA-1D work just as well as the waveterminal for digital to digital conversion?
Is there a way to bypass the waveterminal piece? Does the Edirol UA-1D work just as well as the waveterminal for digital to digital conversion?

How does the Apogee mini-dac differ from the waveterminal for the digital to digtal conversion (since the Apogee has a USB in)? Which is better: waveterminal to mini-dac or USB directly to mini-dac?
If you are wanting to go USB to coax S/PDIF, why not just do only that? The M-Audio Transit or the Edirol boards can be modded to give you virtually jitter-free digital out. Either one can also be installed inside a DAC, eliminating the S/PDIF cable.

I use one of these modified converters with my laptop and Foobar for playback. Foobar and the driver work together to upsample to 24/96. If your DAC can handle this, it is significantly better than the best transport on the market, not "just as good". It is even better than using a DAC to do the upsampling. I have compared 16/44.1 .wav playback to iTunes playback (also can do this) and the 24/96 upsampled by the computer. iTunes is definitely better than 44.1 .wav, but the 24/96 is even better. Forget about "bit-perfect" 44.1. Go with the 24/96 or iTunes and make sure that the converter and DAC supports these.

Steve N.
Empirical Audio

How is transit stock? Pretty good quality?
Why is the mod necessary and how do we do it?

Also, can you explain how to upsample in foobar or itune?

Do they do it automatically, or do we have to do something?

Thanks for the info

Steven N, (Audioengr) I am very interested in your modifications to the M-Audio board and the foobar solution. Please tell us more! :-)
I've used the M-Audio Sonica and switched to the Edirol b/c it sounded better to me... I've now switched to the Waveterminal U24 because it sounds better than the Edirol, and found out the reason may be b/c the Edirol outputs at 48 kHz, not native 44.1 kHz? Dunno if that is the reason or not. I have not compared the Waveterminal to Audioengr's modded Transits (the Sonica and Transit are pretty similar internally)--I gather the Transits do pass 44.1 kHz and respond well to mods. I and not really competent with a soldering iron, however, so I'll leave that to others...
With an Apogee Mini-dac, you just take a USB feed from your computer. No need for any gear in between.