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Music servers and other computer based digital audio technologies.

USB: too complex. SPDIF: too simple.

There are no specs on measuring jitter in audio applications. The effect of jitter is to add phase modulation on the audio signal, and the audibility of this distortion depends on the music being played as well as the spectrum of the jitter. It's not something that is covered by a single number unless that number is just about zero, which is measured in single digit picoseconds. The fabulous AES spent years developing a standard for measuring jitter and failed.

I do not consider an outboard converter powered from a PC to be any different than a device located in the PC box. It all comes down to the quality of engineering and how a particular system is set up. I am running the analog section of the juli@ so I have no digital cables to worry about. I am definitely listening to the clock on the card and through it to the power supply in the PC and whatever noise it happens to have. I have had this card for several years, well before async USB came into use. This is not the greatest converter in the world, but the sound is enjoyable and I would hardly say that I was "essentially screwed" for $150. This card sounds good when run at 176.4 or 192 kHz, which is how I use it. (It does not sound so good running directly at 44.1 kHz.)

I have never been a fan of USB, going way back when USB was still under development. It's absurdly over complicated in the Intel tradition of hyper baroque engineering. On the other hand, SPDIF is too simple, not designed with a proper clock architecture. IMO the best method of sending digital data between two boxes is something like I2S but with the clocking coming back from the DAC to the transport. No unnecessary multiplexing of clock and data on the same wire, which avoids signal dependent jitter created by inter symbol interference, and the destination clocking eliminates the need for phase lock loops or other expensive and/or ineffective mechanisms at the DAC. Unfortunately in the long tradition of consumer audio the best technical solutions never are standardized in the marketplace.



"Make things as simple as possible, but not too simple."







Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar


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