In yesterday’s post, I made the point that regardless of the delivery method—transport or streaming—identical digital audio bits received at the DAC should sound the same.
They do not.
Why?
Let me first start with a little story. When we had the opportunity to listen to the PerfectWave SACD Transport (PST) for the first time, we had high expectations. Inside was a new way to handle bits: an extension of the work we had been pursuing for years, the Digital Lens.
A DL is a big buffer with a low jitter fixed output clock. Bits go in one end of the DL, gather together in a holding pen, and then when the jitter-free output clock has the “time” (pun intended), it pulls from the holding pen the next set of digital audio bits to send to the DAC.
The lowered jitter produced by the Digital Lens provided a revolution in sound quality.
What was different inside the PST—the new innovation we had been sitting on pins and needles to hear—was more than just a DL (we already knew what that sounded like). The PST’s internal DL had been galvanically isolated as if it were an entirely separate entity from the PST. We had built this new structure in the hopes of removing the last vestiges of sonic degradation: noise and jitter introduced by the power supplies and shared grounds inside the transport.
It worked. The sonic differences between the new PST and the older DMP it replaced were more than just better. They were extraordinarily better—a first-note-obvious better.
And therein lies what I believe to be the answer to yesterday’s question. Identical bits cannot sound different unless something else has changed. That something else is noise and induced jitter on shared grounds.
Which is why, in large measure, digital audio received from a computer via USB sounds remarkably different than the exact same bits as received from a transport.
It is not the veracity of the bits but all the baggage associated with the gathering and delivery of those bits.
As is almost always the case, it’s more than what’s obvious.
Paul McGowan / PS AUDIO
