Vfet / SIT Amplifiers

What the VFETs have going for them is two things.


The first is that its possible using them to design an amplifier that will make the lower ordered harmonics (2nd or 3rd) as the primary distortion component, in enough amplitude to mask the higher orders. This results in a smooth sound and might be an order of magnitude lower than a tube amp of the same power (and lower output impedance too).

The 2nd advantage is that of soft clipping, but this is somewhat ameliorated by the fact that nearly all the designs *manufactured* employ feedback, and when you do that soft clipping isn't a thing so much.

You can build other kinds of amps that can get the same distortion signature. One key element is to insure that whatever the distortion signature is, its consistent at 100Hz, 1KHz and 10KHz. Some of the VFET designs seem to do this (so do zero feedback designs regardless of tube, traditional solid state or class D, so long as the bandwidth is wide enough).


It is nice when you get get an amp to perform that way as the improvement is easily heard and the system sound is all about the music- you can forget about the system making it.

Still better than almost anything on the market today, though.

Ha! Not buying that for a second. Not saying its not nice though.

@zm Me too. You might take some of my comments that were previously misdirected, and scrutinize your preamp. It should not be a volume thing that make an amp 'wake up', unless it has a malfunction (which, to do that, would probably be bias-related). But if the amp seems OK, really take a hard look at the preamp.

I hope I was able to clear any misunderstanding.

@sonetduo  You did- I realized reading this that I had conflated some of your comments with that of another poster. I was addressing his comments, not yours, but with the idea that he was running the Yamaha. In a nutshell, I blew it. Sorry about that.

@sonetduo I love the idea of a SIT-based preamp! The problem here is the Yamaha is far too complex. When you're dealing with purist amps and speakers (and let's be clear here- people these days that insist on crossover-less single-driver speaker tend to be on the purist side of things) the least circuitry you can get away with (without making it **too** simple) usually the better. That Yamaha has its heart in the right place, but it has a lot of encumbrance. It would be really interesting to find out how it sounds with no tone controls or tone control switching, just done in a simple no-nonsense approach. 


Now as a designer, the idea that an amplifier needs to hit a certain power level to 'come alive' is disturbing. I have a VFET amp that was designed by Nelson Pass and it certainly does not behave that way. This makes me think that its the Yamaha that is why you are saying what you are. In looking at the preamp and its signal flow, apparently its equipped with a loudness control in addition to a volume control. Your description matches that of the loudness being improperly set. If this was my preamp I'd be cutting all that extraneous stuff out of it. Since that would ruin whatever collector value it has, it seems prudent to me to just go to the type of circuit that the SITs behave as anyway- triodes.

I love the idea of signal-level SITs; I wish they were commonly available.

I have not tried anything else other than the Yamaha C-1, but I probably should

@sonetduo Yes. Your Yamaha is outclassed by the amplifier. You might try a tube preamp; I think you'll hear a transformation.