When I talk about digital sources, most people think of the DAC first. It gets the glory. But before any digital-to-analog conversion happens, something has to retrieve the data and get it to the DAC cleanly. That's the transport's job—whether it's spinning a CD, reading an SACD, or pulling files from a server.
You'd think this would be straightforward. After all, digital is digital, right? Ones and zeros either make it or they don't. But anyone who's compared transports knows it's not that simple. Two CD transports playing the same disc through the same DAC can sound noticeably different. The differences aren't huge, but they're real—and once you hear them, you can't unhear them.
The reason comes down to timing, noise, and power. A transport doesn't just read data, it also generates a clock signal that tells the DAC when to convert each sample. Even tiny amounts of jitter—timing errors measured in picoseconds—can smear the soundstage or flatten the sense of space. And if the transport's power supply is noisy or its mechanics vibrate, that noise can leak into the signal path and muddy what should be pristine.
We learned this early on when building our first CD transports. We'd measure everything perfectly, yet two units with identical specs would sound different depending on the quality of the clock circuit and how well we isolated the digital sections from each other. It's one reason we took transport design so seriously when developing the PMG Signature SACD transport—not just as a data reader but as a precision instrument.
Today, many people stream instead of spinning discs, and in some ways that's easier—no laser, no motor, no spinning platter. But the core challenge remains the same. Whether your source is a high-end SACD transport or a Roon server, its job is to deliver the data intact, on time, and without adding noise. When that happens, the DAC has a fighting chance to do its job right.
And that's when digital stops sounding digital and starts sounding like music.
