Paul McGowan writes:
Here’s another thought on the continuing discussion of why a preamp matters in the chain. Perhaps it’s the DAC’s volume control itself.
One thing is obvious. A DAC without an integral volume control cannot be used without a preamplifier; either separate or integrated. Thus, when we think of why preamps matter with DACs, we’re only discussing those DACs with built in volume controls. And there’s a suspicion that it is the volume control itself that might be the culprit. So let’s take a look.
Using our DACs as examples, we start with the PerfectWave, Mark 1 or 2. The digital volume control on this instrument was lossless at any setting above 50. In other words, from 50 or higher, no change in resolution took place at any volume setting. A free ride. Our newest DAC, DirectStream, takes this a notch higher. Designer Ted Smith figured out a volume control that has zero loss at any level setting–a major achievement. So, how could a control with zero resolution be suspect? That’s a question I have been mulling on for some time now.
One piece of the puzzle seems obvious. We know that tiny changes in the way internal FPGA process are organized make significant differences in sound. Even changes to the display affect sound quality. It’s a delicate process when jitter, power supply and the tiniest of changes can be heard and must be attended to. What’s to stop us from believing that different level settings have different sound qualities–despite the fact there are no measurable resolution losses?
Were it to be found true much would be explained. For instance, we know not all preamps sound better than DACs directly into power amps. In fact, most don’t. This observation lends credibility to the explanation that it is not preamps that make DACs sound better, rather, it is preamps helping DACs not sound worse. This theory can only be true if the preamp is of sufficient quality to add less degradation than using the DAC’s volume control. That all kind of makes sense.
But, just because something makes sense, doesn’t mean it’s true.
How do we make this determination to see if this theory holds water? The first thought that comes to mind; use the preamp as a baseline and try the DAC at different volume settings. Only, there’s a fly in that ointment. A preamp’s performance differs at each level position on the volume control–turn the DAC’s volume down and the preamp’s up, to compensate, and we have changed too many variables.
But, for now, we’ll keep this idea at the forefront of our thoughts and research and revisit this subject when progress is made.