X-PSU V3 and double X10 V3 tube output buffer

While everything in the signal chain adds one distortion or another, this is hardly all that a buffer does. The primary function is to present the driving component with a very high impedance, which makes it easy to drive, particularly for the IC based outputs of many CD and DVD players. It also has a low output impedance, which makes it very tolerant of driving long interconnects or components that have low input impedances; just the types that give the previously mentioned CD players problems. In such systems, the trade off of a small bit of distortion will be an acceptable price to pay for the enhanced dynamics and better frequency extension that can be provided. This is precisely why passive preamps should only be used with the proper combinations of components and active preamps are much more common.

Amen! Viridian (if you'll allow the expression).

NO one can hear less that 2% distortion differances anyway, and most speakers have anywhere from 15%(Great Speakers) to 40%(Avg speakers) distortion figures anyway. So adding a % or 2 or .005 or whatever is NOT what you are hearing-whether you like it or NOT!!!