Anyone who is considering upgrading an AVA 350 to the 400R and is wondering if it is worth doing, it certainly is. I notice that bass is tighter, vocals are fuller and sound more life-like, and guitar sounds more "real". I compared "stairway to heaven" from LED ZEPPELIN IV (Definitive Collection) on both versions of the amp. Robert Plant sounded like he was in the room. The solo at the end by Page sounded brite and shrill on the old version. After the upgrade, the solo was smooth but not TOO smooth. It sounded more like you would expect a guitar to sound like.
Next I wanted to try a good but poorly recorded album BLACK SABBATH "Born Again" (2011 Sanctuary Records Remaster). The bass is muddy and the album is very "Noisy". Iommi's guitar solo at the end of "Trashed" can kill a chicken! After the upgrade the bass is tighter and more defined. Iommi's solo is still brite, but nowhere near as bad. Ian Gillan's vocals sound MUCH better and life-like. If this upgrade will make this album sound better than it ever has, then imagine how nice STEELY DAN's "AJA" will sound. If you are undecided about the upgrade, I highly recommend it.
PS:
My system consists of:
AVA Fet Valve 400R amp
AVA T8+ pre-amp
AVA Ultra 2 DAC
MAGNEPAN 1.7 speakers
Blue Jeans Cable and IC
-NIGHTFALL1970