Definitely do the conversion outside of the computer. Get the USB DAC.
While the sophisticated engineers among us will argue that USB is also frought with problems, there is no doubt that SPDIF is second only to the transport itself in introducing 'stuff' into the signal path. More specifically I should say the implementation of the SPDIF interface - with special emphasis on the bad boy cable...
In a perfect world, the DAC would take in the USB signal and convert it to I2S instead of SPDIF. But even if it simply converts it to SPDIF before sending it to the DAC chip, it at least eliminates the output>cable>input problems.
All that said, while you hear it??? YMMV
BTW, for the record, I am definitely NOT a fan of the Benchmark DAC. Since your question was very specific to that DAC I answered specifically the question you asked. I should probably add that I found the Benchmark to be too harsh for my ears in two different systems I tried it in at length, as well as in a friend's system briefly. It is a very analytical and detailed DAC. I'd associate it more with its Pro-Audio origins. I had a Wavelength Brick that I liked very much, and would guess that Jeffrey Bowman's recommendation of their Cosecant would be more to my liking as well. To use the common vernacular, the Wavelengths are more musical, softer-edged, and warmer - that from my experience with The Brick, and from what I've read on his other DACs. Benchmark are more analytical, neutral, and hard-edged to my ears. Some folks like that kind of sound, apparently. I'm not one of them.
Well, you guys make some great points. My system so far is krell 250m monoblocks going to nht 2.9 speakers, so am a little concerned about the overly analytical sound. I'm pretty sure I want balanced outs of the dac, so should probably do some more legwork on figuring out the dac options. So far i have done a little reading on:
apogee mini dac
grace headphone amp
I know that benchmark has a 30 day audition, pretty sure i can get that with the apogee, if I can swing that with the wavelength i might give that a try a the same time.
Haven't heard the benchmark, but have had lots of experience with both the Brick and the Cosecant, (both being used with apple lossless files on a mac mini) and the Cosecant is one of the best sources I have ever heard- right up there with the infamous Meridian signature reference 808 CD player (the best CD player I have ever heard). Either way- USB is the way to go, being that it is bi-directional and essentially syncs itself, eliminating any clocking or jitter issues that you might find on an SPDIF device.
This forum seems like the place to ask this question: What is the best combination of outputs/cables/inputs to go from a MacBook Pro to a CD player with coax and optical digital inputs? I'm currently using a Van den Hul cable that is a miniplug at one end (plugging into the MacBook), and Toslink at the other (plugging into the digital inputs to my MF Tri-Vista SACD/CD player). Is there some better way (i.e., better sounding) of connecting the computer to the Tri-Vista? Is there a cable that is USB on one end and coax or Toslink on the other than would give better sound than mini to Toslink?
Bruce - your current arrangement is less than optimal, IMO. You should use an external USB/SPDIF convertor. This would add a standard USB cable to the equation, as well as a digital cable of your preference (Toslink or Coaxial) depending on the device. The latter would go to the digital input on your MF. Empirical Audio's Offramp would serve that purpose. I use a Waveterminal U24 for the same purpose, but those are no longer avaialable, or I would recommend them. I believe Hagtech offers an alternative, as do several other companies, both in pro-audio and specialty audiophile. They are available at various pricepoints, as most things in this hobby. You can get a convertor from PartsExpress for $20, or spend $1K+ on one from Empirical or spend several thousand on a new USB DAC from Wavelength. Since the conversion and clocking is critical I'd say it's an investment you shouldn't take lightly (skip the Parts Express route). The idea is take the conversion of your computer audio files output, into SPDIF, outside of the electro-magnetically noisy environment of your MacBook (where it currently is taking place given the arrangement you describe). USB seems to be the best interface for doing that. I'm no expert, consult someone like Steve from Empirical, or Gordon Rankin from Wavelength for various points of view on the subject, complete with technical details up the Wazoo. There are also plenty of threads in the archives here and over at PCAudioAsylum that may give you additional real-world opinions and advice. I think most would agree that getting the coversion/re-clocking out of the noisy computer environment will be a significant improvement.
Thank you very much for the very informative reply. I don't know if I was the only one helped by your response, but you certainly helped me. I will begin researching what is the most cost effective way of converting a USB signal to SPDIF. Given my level of involvement in this hobby, I'm afraid I know which end of the cost scale I'll end up at! Thanks again for your help.
I'm actually quite impressed with the sound quality of the current set-up (Mac->optical cable->MF Tri-Vista), and find it sounds as good (some listeners I've had over say "better than")as playing a CD using the Tri-vista as both transport and DAC. However, as a card carrying member of the audiophile community, I'm always interested incremental improvements in sound quality. In my case, I would add "Cost effective" to that search. That is why I was hoping for a relatively inexpensive cable solution to improving the sound quality. I'm not going to spend a thousand dollars on this unless it makes a discernable improvement over the current set-up. Howver, if I can do a lot better than I am now with a relatively small investment, I'll do it. I would like to try it out before making the investment though.
Bruce_1; you are welcome. Definitely get some input from the folks who make their living in that field, and listen and weigh the specific alternatives yourself. Report your findings here when you have...perhaps another thread. Have fun! Worst case scenario - it does sound like you have an enjoyable system already - Nothing wrong with that!
Hey Rene - How have you enjoyed the Wavelength Brick? Did I describe the sound in a way that was similar to your own impressions of it? Have you held onto it?
Marco (Jax2), I got the Brick and I am holding onto it. Your description was on the dot - relaxed and smooth, very natural sounding with solid midrange, solid images and deep soundstage, good separation between instruments, every instruments is well defined sonically and spatially. The bass can be a little on the soft side, but I did notice some reaction to tube rolling. I am able to get closer to a solid state type bass and top end extension, but at the sacrifice of some of the positive qualities. I just got some more tubes for tube rolling (Mazda triple mica etc.) to play around soem more. Overall a slightly different sound and presentation from my Audio Aero Prima, but with similar strengths. The Prima seems to ad some more resonance and texture, while the Brick shows more realism and a more natural sound.
Thanks again for all your help and comments :)
Own the Cosecant, owned the Brick-both incredible products...Have done exhaustive research on this matter...Choose whatever DAC you like, but I can tell you from experience of going through the Computer DAC "as a front end route", and listening to alot of different DAC's (from Benchmark to Levinson) the Brick from Wavelength betters the Benchmark in spades. For $700 bucks or so more than the BM, it's a no brainer IMO. The USB controller in the Wavelength stuff is also custom designed by Gordon, not a commodity-based DAC chip like just about everything else out there with a USB interface at the moment. To me thats makes Wavelength VERY special indeed.
To answer your question though:
USB is a bi-directional connection, so jitter is dealt with very effectively-on the way in, and therefore corrected on the way out. I believe on Gordon's site it says jitter is eliminated actually, could be mistaken though.
SPDIF is not bi-directional, therefore requires clocking to deal with jitter. It was never designed to do what we do with it in hifi. So to answer your question USB is a better choice of the two, sonically, and practically.
Whether the future brings a better connection than USB at some point remains to be seen. But one thing is for sure, my current USB/PC based is the BEST digital I have ever heard, and I have heard alot.