Here are some of my impressions of the amp so far.
I met David (909) at Craig's house on Saturday to pick up my Equilibrato and all I can say is that I am extremely pleased with this amp. David was kind enough to bring over his L3000s, a really great sounding cartridge and phono preamp. We did quite a bit of listening to both CD and vinyl on Craigs Sony PSX70 turntable.
The Equilibrato with the PX4 sounds great, it is very musical. Listening to some vintage vinyl really made me want to setup my turntable and get my analog system setup again. I've been listening to music digitally through my Lavry DA11 quite a bit lately and although it is convenient and does sound great with the Equilibrato, I do miss the analog sound.
In regards to balanced versus unbalanced, I did listen to the AD2000 and RS1 balanced vs unbalanced, and there is a noticeable difference in soundstage and definition. The balanced setup definitely sounded better to my ears. Now to I need to get my headphones balanced.
The input switch on the front lights up when you turn on the amp, it glows a nice amber / orange color that almost matches the glow of the tubes. Very cool. It does not change color, just goes in and out to switch between the two single ended inputs. Nice, now I don't need a seperate preamp. I can use one input for digital and one for analog.
The Sophia Electric PX4 sounds great, it is a little bit microphonic, but nothing that I can hear in normal listening. I didn't compare it to any 300Bs, but am quite happy with my decision. Although I do want to listen to the much more expensive KR tubes, Craig says that they sound better overall and have better bass.
This amp is a huge leap forward in performance over my DM-2 prototype, it is better in everyway from detail, soundstage, etc.
