I am curious if anyone has tried the USB connection from an HTPC listening to audio. I would be interested in comparisions using analog out of the HTPC and/or spdif connections (also need to know what soundcard you are using and format, .ape, flac, etc..). It seems to me that going straight to the DACs in the 990 should offer some improvement.

Thanks guys!
Ed

I have a USB AUdigy card.
Basically the USB slave device steals the regular audio from the card, so I took it out and I am just using the SPDIF since that will carry both Dolby Diugital, DTS, and PCM rather than just PCM.

Howevr, I didn't hear any difference between the USB and the PCM on the SPDIF. Of course, as both signals are digital and being processed in exactly the same way (in the 990) I wouldn't expect there to be a difference.

Thanks for the feedback Cerebus. It is my understanding that you are bypassing the soundcard when using USB and that the data being sent USB does not have jitter and timing (USB is asynchronus) errors that you get with SPDIF. I am no expert on this and am really just starting to read up on it in the Audio Asylum PC Audio section. I am considering using an external USB DAC between my PC and 950, but I wanted to know if the 990 scenario was comparable.

Thanks again!
Ed

USB audio drivers resample all input to 48khz in line with AC97 specification. (AT least all USB audio solutions that I've ever seen do this.) So if you are interested in transporting pure 44.1khz digital CD-audio to your processor from your PC, using USB, then you are not getting a bit perfect signal. You would be sonically much better off using the digital out from a non-resampling sound card, which by the way rules out the Audigy line immediately. You would also want to find a sound card that has an ASIO driver, so that the windows kmixer (which is sometimes called the kmangler because it mangles the audio bits) would also be taken out of the mix.

A really good soundcard for all of this is the Terratec DMX 6fire card. Excellent all around, and in fact even its onboard DAC probably sounds as good or better than your standalone CD player.

Thanks Newbuyer. I believe your statement "USB audio drivers resample all input to 48khz in line with AC97 specification" is true for USB soundcards, what I am referring to is a USB connection to a DAC that is taking the digital info directly from the source (HDD or CD Drive) and sending it unchanged to the external DAC. At least that is the way I understand it works at this point, I am still researching this issue. I have been using an M-Audio AP2496 for about 4 years, the conveinence of the HTPC as a music server is great, I am simply trying to find a way to improve the quality of 2 channel music reproduction. I believe the way to do that may be to move the DAC outside of the PC. I can use the analog out and use the bypass mode, and the spdif out moves the DAC to my 950, I just want to make it even better. Thanks for responding.

Ed

A personal story: I have used the optical SPDIF out from a Terratec DMX 6fire LT card to an external M-Audio SuperDAC to a preamp. Perfect CD images were stored on HDD using ExactAudioCopy and played bit-perfect using WinAmp with ASIO plugin. I thought it worked very nicely, and when the HDD electronics are used as transport I don't believe you need to worry about jitter or errors like with CD transports.

I *believe* that any USB solutions like you are describing can read music datastreams directly from CD/HDD but will resample/reencode to 48khz before outputing through USB, due to constraints and implementation of the internal Microsoft USB audio driver. For instance, I believe the external M-Audio USB solution you are using can record to 44.1, but will only read/output at 48/96khz, yes? Or at least it cannot output unresampled 44.1?

Sorry that I can't say with greater certainty about any of this, but I share your interest...