I used Wavac SET amps in the past. I still have them them and use one in Santa Cruz, delightful sounding amps.
In the main system, I replaced them to good effect with vintage VFET (SIT) amps fronted with directly heated triode drivers. It works a pip, and after warm up, I would bet any blindfolded listener would peg the result as ultra clean sounding tubes. More power, better dynamics, detail and space with a small sacrifice in that golden, lit up sound from the Wavacs.
I bought a First Watt M2 a couple of years ago out of curiosity and as a back up, 25watts class A going up to 40 watts at 4 ohms. I got a deal on it as a demo, but it arrived in a sealed box with all the papers and warranties, so I think it was actually new.
I only used the M2 once in a while to test and play with, but mostly it has sat idle. I thought the VFET amps sounded better, and although M2 had some alluring traits, I thought it sounded a little wonky and odd. I almost sold it, but kept it out of general laziness, like a bunch of other stuff I have that I have been too unmotivated to sell.
I thought one of my VFET amps may have had a problem recently. It didn’t, it was just a loose speaker cable, but I put the First Watt M2 in the system for a bit. I decided to give it a full court press audition at last, and left it on for a week. At times, I would listen to it playing just the midrange ribbons with the crossover (covering 350 Hz to 7000 Hz), at others, listening full range without a crossover using the Analysis Epsilon bass panels as full range speakers.
As a result, I have seriously upgraded my opinion of the First Watt M2. I gather it was never given the hours of run in it needed, and all of my brief turn ons never allowed it to break in. i do remember that I thought vocals had a see around the corners quality with M2. That quality was probably most epitomized years ago when I heard vocals on Steve Williams’ big Wilsons speakers with Lamm M3 amplifiers. The Lamms were warmer, but I was surprised the little M2 was able to catch that quality.
All the wonkiness disappeared after a couple of days. It is a smooth, detailed, and spacious amplifier. I can’t say it is worse than the VFET any more. The VFETs dominate in spatial location albeit with a lovely envelope of sweet sounding tonal decay. However, the M2 is fuller and where the VFET will decay sweetly, the M2 will punch. It seems that the VFET and M2 are different but equal on detail retrieval.
I lack the vocabulary to describe the M2. It is just different sounding than either tubed or transistor amps I have heard to the point of just saying it is unique to my experience. I sure wouldn’t call it very solid state sounding, but not tube, either.
One quality it has that I really like I can only describe as high contrast gloss. Where typical SS amps glare, gray, or smash the sound image up against an invisible 2 dimensional plane, the M2 remains three dimensional, but creates a bright contrast that is not at all glaring, it contains definition and information. This makes things like massed strings and brass sound very alive and life like. High frequencies and decays are brilliant and colorful.
Strange, I thought about selling the M2, but now I am going to keep it. So much for listening to stuff that hasn’t been broken in properly.