Hi David. My ZROCK3 arrived and though it only has about three hours on it now it does sound distinctly different from the ZROCK2 (which is about four years seasoned) and it should as it has different caps, a different transformer and even different wire and a changed circuit.

I like what I hear. Worth waiting for.

I found that the up position was the "B" EQ Curve as well on mine, which differs from my ZROCK2 components. And with the down or "A" position there is definitely treble reduction. I would recommend experimenting adding the gain from the back--adding the gain as well as the EQ yields more discernible effects in my experience so far.

Ad for music. . . I would just listen to albums that you really like and see what the effect would be while manipulating the knobs, and also listen a recording that you may have found thin or wanting before and see if the ZROCK3 can flesh that out. In my case I listened to a very familiar recording, Duke Elllington "Indigos," and that is fleshed out a bit in bass and the "room sound" and I also spun a King Jazz cd of Billie Holiday--these early digital discs are really nice transfers but seem on my system to be a bit thin and edgy--twisting the knobs helped me find a more relaxed sound.

I've had my ZROCK3 for nearly 2 weeks now and I stand by my original recommendation: listen to favorite and very well-known material and you will hear the effects, and hear the effects evolve as it seasons.