External USB sound card, digital out - Page 2

OK, so I tried Wodgy's trick with the DD files encoded as PCM being sent to my HT receiver, and it didn't work. Playback a normal MP3 or WAV file, no problem, playback of that thing, nothing.

I also tried using the computer to capture the USB audio out when the DP-U50 was being fed SPIF by my CD player and comparing the captured signal to the original ripped from the CD, and inverting one and pasting them on top of each other, and I did not get a perfectly flat (i.e., zero signal) result.

This strongly suggests to me that the digital output of the DP-U50 is not bit-perfect. Bummer.

Thanks for doing the experiment and sharing your results. If you're not already using a player that supports Kernel Streaming (e.g. Foobar), you might want to give that a shot. On some setups it makes things bit-perfect (it's not a magic bullet, but I have seen it work). If you're not familiar with Foobar, remove all the DSPs, even the volume control, set output format to 16 bit fixed point, turn off replaygain, turn on kernel streaming.

My guess is that this card might be bit-perfect under Linux, assuming it has proper drivers for that operating system, since we know it can output a 44.1kHz signal.

It's on a tab called "Output" which is a subitem of "Playback". (You also need either Foobar Standard or Foobar Special to use it... it's not included with Foobar Lite. They're all the same; Foobar Lite is just a smaller download.)

If you don't want to redownload FB2k the Kernel Streaming component is available on the Foobar2000 website in the Components section.

Sounds like the new install didn't quite work. With Special you should see five things in Output:
* waveOut
* DirectSound
* DirectSound v2.0
* Kernel Streaming
* Null output
Not sure why you're not seeing this. Maybe reboot?

Edit: Kernel Streaming is not available on Windows 95/98/ME.

No problem, though I still wonder if there's something else I can do on this...

I'm using a Mac, actually, OS X 10.3.

To do the file comparison, I hooked up my CDP optical out (which we know is not resampling) to the DP-U50, and the U50's optical out to my G5's on-board optical in, and just did a straight capture. The signals look very very similar to the naked eye, but the invert-and-mix never gave me a flat result (which it does if I take the original, duplicate it, invert, and mix with the original). I tinkered with a bunch of different offsets to try to get it right but nothing gave me a flat result. Thus, I don't think they're identical.

For the HT test, I hooked up my PowerBook (wasn't lugging the G5 into the living room) to the U50 and the U50's optical out to my HT receiver (NAD T751). Playing regular sound files through iTunes or whatever worked fine, but the DD-encoded WAV just produced silence. In that case I do wonder if there's something the OS is doing to munge the signal out the USB port, but I'm not sure.

EDIT: That said, I'm still happy with the DP-U50 as a USB DAC/ADC and input switcher. I think it sounds better as a DAC than my Sonica (probably the external power supply), it does downmix DD and DTS 5.1 to 2-channel pretty decently (I have a TV with digital cable in my study/listening room, and the 2-channel analog out sucks, but it produces digital out), and for under $150 shipped, that's still a pretty good package deal.

My old computer uses Win2K, i had to install Kernal Streaming seperately

Actually, it was the quality of the digital out that I was trying to assess. I thing the analog out is pretty good for what this cost--it's easily comparable to a middle-of-the-road CDP. (Though certainly not to a Benchmark DAC1, as you can attest.)