Any insight with the Berkeley Alpha DAC ..??

I'm not technically knowledgeable about computer audio, so I'd like some help understanding why Reference Recordings recommends the use of a sound card in the playback equipment (BTW, I own a number of RR CDs and am glad it is back in business).

From what I know, the original sound cards were an all-in-one device that first converted the digital data from the hard drive to SPDIF and then converted the SPDIF to analog. It may have even amplified the signal after the final conversion. The sound card also took the SPDIF feed from the CD-ROM and converted it to analog. The net result was that speakers were the only sound equipment external to the computer needed for playback.

Audiophiles rejected these sound cards in favor of external conversion devices because (1) the noisy electronic environment inside the computer created distortion, (2) sound cards were cheap devices made to a price point to sell as part of the computer package and (3) sound cards limited the type of sound produced and external DACs did not. As I understand it, quality computer audio systems bypass the sound card for conversion to SPDIF (and therefore for conversion to analog too) by taking the digital feed from the hard drive outside the computer. If this is so, why is it necessary to use a “high quality” sound card or any sound card at all? Does the sound card perform some other functions that require very high quality parts or sophisticated design? Or does the Berkeley Design Alpha DAC perform only the conversion to analog, leaving the conversion to SPDIF to the Lynx AES? If so, why not substitute a good quality USB DAC for the Berkeley?

I think you need the sound card in order to pass the 24/192 in all its glory.

Dougmc wrote:
"As I understand it, quality computer audio systems bypass the sound card for conversion to SPDIF (and therefore for conversion to analog too) by taking the digital feed from the hard drive outside the computer. If this is so, why is it necessary to use a “high quality” sound card or any sound card at all?"

There are two ways to get audio data out of a computer:
1) using the audio software stack
2) using network - ether net/WiFi

#1 can output data three ways:

1) USB to S/PDIF converter
2) PCI bus using sound card or on-board logic with S/PDIF output
3) Firewire to S/PDIF converter

There is no direct S/PDIF from a computer. It must implement one of these three in order to get S/PDIF digital output. If it appears that these are "bypassed", it is because #2 is implemented on the motherboard. It is still there, not bypassed.

"Does the sound card perform some other functions that require very high quality parts or sophisticated design?"

Each of #1-#3 require high quality parts and low-jitter clocks to achieve good results.

Steve N.
Empirical Audio

Steve, is there any inherent advantage to any of the three approaches? Specifically, on a Mac, one could go out via any of the three -- USB, Firewire, or S/PDIF via the optical out. Which is better? And for the future, when we can hopefully expect to start downloading 24/96 or even 24/192 music, which solution will support the high rez stuff and be most future proof?

Drubin - as for devices that use the audio stack in the computer, they are all the same in theory. However, the implementations and protocols used make some devices superior to others.

PCI cards are the worst because they rely on too much of the computer infrastructure, including the clocks and power system. Outboard converters, both USB and Firewire are generally better. However, there are good and poor chips available for both USB and Firewire, so it depends on the chip that was chosen for the converter, as well as the implementation.

By implementation I mean the Power System, PC board design, circuit design, cabling etc..

24/96 is supported on some USB converters/USB DAC's that use the TAS1020 chip from TI, as well as some Firewire converters. Only a couple of PCI cards support 24/192 at low quality, however they can be reclocked to provide high quality 24/192.

If you have to have 24/192, then a PCI card driving a reclocker is the best solution. If you are happy with 24/96, then USB is the best solution IMO.

Steve N.
Empirical Audio