[sbrtoy]

Hello all,

I have been doing a good deal of listening comparing vairous digital feeds, and wanted to post my results as well as ask others for theirs.

I have done comparisons of the USB output from my Mac Mini with both ALC and WAV files, and compared this to a redbook player as a transport. All this is done through a PS Audio DAC III run at 192khz upsampling through our soon to be released monitors which are extremely revealing of these type of changes.

My opinions are very much subjective, but what I can consistently identify is the USB has greater high frequency detail and extension with either ALC or WAV files, and also delivers larger soundstage width and height.  The USB input delivers more midrange and treble transient punch, but lacks some of the midrange body of the SPDIF.  Vocals sound leaner and you hear more of the breath and the reed on saxophones than you do the "body", almost like it is miked closer. I also found the USB connection allowed different speaker camber as the wider and more delineated soundstage allowed for less toe-in while still delivering  specific and forward vocal placement.

The normal redbook SPDIF connection has a warmer sound with better soundstage depth, however it lacks definition, particularly in the higher range from 7000hz and up.  Many would say it sounds more "analog" though I have heard vinyl setups with better definition than the SPDIF input.  The SPDIF also seems less dynamic and it homogenizes complex passages more than the USB.

My personal preference is the USB at this point, however there are many who would prefer the warmer sound of the SPDIF.  Anyone else care to comment on what you have heard in regards to this comparison?

The great news is, we are just seeing the tip of the iceberg for PC audio, whereas SPDIF seems to be approaching the zenith of its sound quality. Perhaps direct I2S or Firewire solutions will open up even better options for DAC connection soon.

[Crimson]

Hi, great post. Subjectively speaking, I really only prefer USB over SPDIF when going direct to I2S (Scott Nixon, Wavelength, Empirical). A very analog-like sound, but with great dynamics and detail. Prior to this I tried a few USB-SPDIF converters (Trends, Hagerman) connected to my favorite dac-du-jour, but found no perceived benefit over straight SPDIF. Different? Slightly. Better? Not really. I have no affiliation with Scott Nixon, but his USB TubeDac with the upgraded power supply was an eye-opener: Direct to I2S, filterless, non-up/over-sampling, no frills dac. The music just flowed. I've since upgraded along the same topology with a Wavelength dac and I don't think I'll ever ever go back to playing a cee-dee.

A question: Did you try the comparison without upsampling, and if so, were the differences the same?

[sbrtoy]

Crimson,

Thanks for the reply, as far as the upsampling the PS is only switchable between 96 or 192khz, and I prefer the 192 though some people think it is too dry.  The difference between USB and SPDIF is similar to switching to 96khz, you lose high frequency definition and soundstage but gain a somewhat warmer sound. 

I agree that the USB to SPDIF switchers are pretty much equal to normal CD playback, I found no improvement to them even though they do open up a way to play from a PC without a USB DAC.  My interest in the I2S and Firewire is more along the lines of bypassing USB altogether as it was not designed specifically for audio and thus some feel it has limitations in this capacity.  It is kind of like jitter, no one even knew about it or had ideas how to prevent it for a long time with SPDIF, so I am sure USB will get this treatment as well.

Anyone else compare SPDIF to USB on their DAC's?

[alexd]

Hello all, I am new to this forum, however, I am a chief designer and president at 3 Dimension Audio.
I have specifically looked at the differences between USB and SPDIF uses for audio.
Well, I must say, that USB has its merrits over SPDIF. The main difference is jitter. In well designed USB front end the jitter is lower by 60% over best SPDIF.
Most DAC's on the market do not do anything to reduce this jitter. At 3 Dimension Audio we have created the DAC, that completely ignores input jitter, in fact the DAC IC never see's input clock.
It uses our internal clock generator with rms jitter less than 3 pS.
In our listening tests, nobody could detect the difference between USB and SPDIF inputs at all!!!
if interested, take a look at our web site: www.3d-audio.com

[Jon L]

As someone who's been experimenting with "PC audio" for a long time, it seems important to me that as PC audio becoms more widespread, it is helpful to define what each term really means to even have a coherent discussion about the topic. 

For example, people who use Mac's cannot assume they're talking about same things as PC users because the basic foundation and audio stack, therefore sound, of each platform is different and software available for each platform also make a large difference in sound quality.  Linux also throws another large variable to the mix.  Case in point, I had the same PS audio DLIII DAC with my PC and had basically the total opposite sound signature from its USB input and spdif input from the OP. 

It's also important to precisely explain what one means by "redbook player as transport" because these vary hugely in their own sound quality and signatures, so much so that their own differences can be larger and overwhelm the difference between PC audio and "traditional" audio. 

Many people also seem to almost equate "PC audio" with USB audio with recent abundance of USB Dac's and USB converters, but I think it would be a mistake to start and finish one's PC audio journey with USB audio only without trying other avenues to hear for themselves, e.g. a quality pro soundcard outputting spdif with digital tansformer-coupling.  One may still end up preferring USB audio, but there are definitely other ways to enjoy the benefits of PC audio with superb sound quality. 

To me personally, I try not to get hung up on arguments that PC audio is *superior* to traditional audio or vice versa because IMO, both can be tweaked to sound extremely superb and satisfying.  The main reason for me to continue with hard drive audio is the instant and easy access to all my beloved music, much of which used to languish in multiple CD racks, hoping to see the light of day 

   

[pardales]

I have had the opportunity to own two DAC's (Audiosector and VALAB) which I was able to hear both USB and SPDIF inputs via a HagUSB converter. My transport was a Mac laptop in both cases. In the case of the Audiosector I heard two different units, one was USB input and one was SPDIF coaxial. The VALAB DAC had multiple inputs.

In the case of the Audiosector there were differences in the two versions of the DAC but they were not significant enough for me that I could give one obvious preference over the other. In the case of the VALAB DAC I definitely preferred the SPDIF input via the HagUSB over the straight USB input. Why? I don't know, but it did sound better to me.

One must have a very revealing system to make fine distinctions, me thinks. I think we are just entering the computer audio frontier and I look forward to future development. I set-up my computer transport almost 4 years ago and did so primarily because of how it allowed me unprecedented access to my entire music collection. It was a revolution for me that continues to pay dividends.