PS Audio Announces Fully Balanced USB DAC

kfr01 · « **on:** 18 Jul 2006, 08:14 am »

Verrry interesting. The price seems right.

http://www.psaudio.com/products/digital_link_iii.asp

Bel Canto is also releasing a USB DAC. Twice the price, but includes digital volume control (eliminating the need for separate preamp).

http://www.belcantodesign.com/prod_DAC3.html

Exciting times for computer audio junkies.

Loftprojection · « **Reply #1 on:** 18 Jul 2006, 01:24 pm »

That PS Audio looks really interesting, specially at $999. One thing I don't like in their description is this "finest sounding on the market at any price" attitude. I wonder how much of their sweet marketing talk is real. They seem to say the same kind of thing about all their products...

brj · « **Reply #2 on:** 18 Jul 2006, 01:37 pm »

It doesn't say so explicitly, but I get the impression that neither one of those DACs takes the incoming USB signal straight to the DAC's I2S inputs. It seems they both leave the S/PDIF conversion in between. Does anyone know for sure?

Robert57 · « **Reply #3 on:** 18 Jul 2006, 02:39 pm »

I phoned Bel Canto's Customer Service line a couple of months ago to ask about i2S, and the very helpful guy said they are not using a direct i2S in the DAC 3. He explained they are concerned i2S is not yet a standardized connection and they have instead focused on cleaning up the S/PDIF and the analog stage with meticulous PLL's, re-clocking, and other techniques. So maybe the care in the execution will trump the digital connection technique.

brj · « **Reply #4 on:** 18 Jul 2006, 04:08 pm »

I'm not involved in the field enough to know how close to a standard I2S really is, but it certainly seems to be the interface most frequently discussed. More importantly, however, the Burr-Brown PCM1792 DACs that the DAC3 uses supports the I2S interface (along with "standard" and "left justified").

kfr01 · « **Reply #5 on:** 18 Jul 2006, 05:37 pm »

brj:

I keep wondering the same. Perhaps an e-mail to PS Audio is in order.

I think I'd preorder one if they could tell me that it takes the USB straight to I2S.

kfr01 · « **Reply #6 on:** 18 Jul 2006, 06:32 pm »

I e-mailed. No response yet, but I registered for their forum and here's a post I saw:

"The audio from your computer is sent via the usb audio standard to our dac. It does have buffering and error correction. We then convert it to S/PDIF to avoid the internal dac that is in the usb chip. At this point, the signal is treated just like any other input to the dac. It goes through the same receiver, upsampler/reclocking, dac and output stage as all other inputs.

The current generation of drivers/chips only support up to 48kHz sampling frequencies."

"We are converting to spdif. The entire audio driver is built into the usb spec so whatever comes standard with this interface comes with our product

."

Too bad. Maybe it is still a nice product. The above quote makes it sound like they think it is a FEATURE to convert to spdif. Disappointing, nevertheless.

Bob Reynolds · « **Reply #7 on:** 18 Jul 2006, 06:53 pm »

Can someone direct me to literature explaining the data format used by audio in a USB connection? Also, what is the main concern about converting to SPDIF?

Thanks,
Bob

woodsyi · « **Reply #8 on:** 18 Jul 2006, 07:24 pm »

I2S protocol: http://www.semiconductors.philips.com/acrobat_download/various/I2SBUS.pdf

SPDIF protocol: http://www.epanorama.net/documents/audio/spdif.html

USB protocol: http://en.wikipedia.org/wiki/USB

You can see why converting to SPDIF negates the serial transmission from USB.

kfr01 · « **Reply #9 on:** 18 Jul 2006, 08:01 pm »

The Bel Canto device also appears to convert to SPDIF.

Any reason why these "big boys" aren't adopting I2S internally?

I2S overhyped? Too "fringe" for mainstream products?

Thoughts?

Bob Reynolds · « **Reply #10 on:** 18 Jul 2006, 09:28 pm »

Here's a link, which I haven't had time to review yet, that should shed some light on the data formats used by audio in USB.

http://www.usb.org/developers/devclass_docs/frmts10.pdf#search='usb%20audio%20format'

All data in USB is encoded using NRZI, which doesn't tell you anything about the underlying data format being encoded.

So far, I don't see the issue about taking USB audio data and repackaging it in SPDIF format. Can someone provide more detail? What's the fundamental issue?

ZooDog · « **Reply #11 on:** 21 Jul 2006, 03:13 pm »

Quote from: kfr01 on 18 Jul 2006, 06:32 pm

I e-mailed. No response yet, but I registered for their forum and here's a post I saw:

"The audio from your computer is sent via the usb audio standard to our dac. It does have buffering and error correction. We then convert it to S/PDIF to avoid the internal dac that is in the usb chip. At this point, the signal is treated just like any other input to the dac. It goes through the same receiver, upsampler/reclocking, dac and output stage as all other inputs.

The current generation of drivers/chips only support up to 48kHz sampling frequencies."

"We are converting to spdif. The entire audio driver is built into the usb spec so whatever comes standard with this interface comes with our product ."

Too bad. Maybe it is still a nice product. The above quote makes it sound like they think it is a FEATURE to convert to spdif. Disappointing, nevertheless.

There is another post on that forum from a PS Audio employee following the one that you quoted that reads:

Quote

The receiver in the DAC is used to convert all incoming signals to I2S which is the format that is used in the Upsampling chip as well as the DAC itself. The nice thing about the USB connection is that you aren't relying on your noisy computer to do the spdif conversion. Our usb chip does not use the computer power supply to power the chip, it has it's own regulator. It also has a clean clock to keep jitter in check.

Now I'm very confused. Are they maybe saying that the USB stream is converted to spdif and then to I2S??

kfr01 · « **Reply #12 on:** 21 Jul 2006, 06:30 pm »

Zoo - thanks for seeing that. I wish I knew more about / had time to research more about whether this I2S/spdif business actually matters.

kfr01 · « **Reply #13 on:** 21 Jul 2006, 11:45 pm »

Here's the latest:

"Yeah, excellent but wrong. Sorry. I just went over with lead engineer Jon Magnussen. Here's what you can report.

So -> USB -> SPDIF -> IS2 -> DAC -> clock removed and upsampled

Or -> SPDIF -> IS2 -> DAC -> clock removed and upsampled

It wasn't quite as simple and the USB does have to go to SPDIF first. However! The only real reason any of this SHOULD make a difference is jitter. Fortunately, the jitter isn't changed in either method because the clock is thrown out when it goes to the upsampler.

Jitter is always related to the clock - but because ours throws out the clock, it really doesn't matter."

What think you? I think I may order one tonight. I've been looking for an under $1k way to get into a usb upgrade (from my stock m-audio sonica/transit) and into a DAC with 192k upsampling and balanced outs.

ZooDog · « **Reply #14 on:** 22 Jul 2006, 12:24 am »

I guess that's good news? Right? Maybe someone more digital savy can comment.

I might place an order, too. Don't really have much to lose with the 30 day return policy. I like the fact that it has balanced outputs, too. I'm also using a M-Audio Soncia to convert USB to spdif and I'd like to take it out of the mix.

I was reading some of the other threads in the PS audio forum and I guess Paul McGowan could have priced this DAC at $699 if he ordered more than 500 of them, but he wasn't sure he could sell that many. Assuming the unit is going to sound good, I would think he could easily sell that many with so many audiophiles switching over to PC-based digital front ends. Oh well, $999 is still pretty good considering all the features that this unit has.

boead · « **Reply #15 on:** 22 Jul 2006, 12:32 am »

http://scott-nixon.com/

kfr01 · « **Reply #16 on:** 22 Jul 2006, 01:22 am »

I'm aware of the Scott-Nixon product. No upsampling, balanced outs, or the same amount of drive...

kfr01 · « **Reply #17 on:** 24 Jul 2006, 02:13 am »

Well, I went ahead and ordered the PS Audio USB Dac.

One box. USB in, balanced analog out. No need to send it in for mods, etc. They have a 30 day return policy, so I'll give it a spin and report my findings sometime late August after I receive it.

They claim <50ps jitter levels in spite of the fact spdif is used. I haven't been able to find anything that suggests lower jitter values are audible / distinguishable.

ZooDog · « **Reply #18 on:** 26 Jul 2006, 05:22 pm »

I'm still thinking about ordering one, but I actually need to get a new preamp before I could really evaluate it properly.

kfr01 · « **Reply #19 on:** 2 Aug 2006, 04:22 pm »

Problem.

Apparently the PS Audio DAC uses a generic windows USB driver. It does not support ASIO.

Anyone else think this is a show-stopper? What's the latest thought as to how crappy kmixer is? Has MS resolved some of the resampling issues of the past?

Thanks!

Karl