Several weeks ago, when I read about the new FET-Valve upgrade in this circle, I made a decision. I would get another credit card, and upgrade my 550 EXR. Once I received the credit card, I also purchased an Ultra 350 to tide me over while my amplifier was in at Frank's.
The Ultra was certainly cleaner than the EXR. Transient attack and overall definition was superior as well as imaging information. Yes things were better, and I enjoyed going through my music collection hearing parts of the mix that were subtly buried under the grundge that were a part of the EXR's performance.
Yesterday, my upgraded EXR returned from Frank's. I left work early so that I could retrive the amplfier from my back porch. Downstairs it went and quickly it was hooked up, replacing the Ultra that I had been using. I put on a Genesis SACD that was fresh in my mind as I had seen the concert only a few days before. And I was stunned. A complete layer of "haze" that was there with the Ultra no longer was there. The music exhibited a "stark transparency" that was hard to believe. After living with FET-Valve amps for 15 years this presentation was not just better it was completely better. The distortion factor is so low that elements in the mix, the pans, the movements of the faders became immediately apparent. Simply miked material such as Janis Ian had a voice that floated in its own space, with wonderful coherence and articulation. Material with bass such as Steely Dan "Two Against Nature" was a revelation, as the mix's for the bass, drum and various synths was completely revealed. Extension at both ends of the spectrum was well enhanced, more air, more low bass, and more spacial information for the material.
I went upstairs and called Frank. In the 30 plus years of sending him equipment I have never heard such an upgrade. Whatever I sent him was ALWAYS better and well worth the money, but this upgrade was in another league. I told him he hit a home run with this design and he hit it out of the park. The best money I ever spent in audio.