Quote Originally Posted by REXTON View Post
Please could you do this test as I have a Time Step HE as well and I would really like to know how it measures up against Paul's work.
Now this is interesting and important to understand. What exactly are you going to measure? All the PSUs should generate +21V as near as dammit off-load. If they have half-decent regulation they will also generate +21V while the motor is spinning. You could knock up a four component circuit using a 1.5A LM317 to achieve that and have current to spare. You might just catch a glimpse of voltage regulation on motor start-up on a digital voltmeter, but you'll have to be fast.

The only parameters that might give away the sound quality differences between the PSUs are tightness of voltage regulation while under load and noise performance, for both of which you'll need an oscilloscope.

The only way you're going to be able to differentiate is by listening, I'm afraid.