Evil Joe - FET vs Tube Gain Staging

[Meeotch]

I've been reading up a bit on FET vs tube for gain staging at the amp's input, and it is a really interesting topic. I'm wondering if Jason and/or someone with some tech knowledge could chime in on how a builder might come to the decision to use FET in this regard. There seems to be more talk about it in the context of microphones, as well as acoustic guitar/piezo applications. With a guitar tube amp, it seems like FET can provide even more gain, lower noise, and possibly a more clinical "attack". That being said, it is less common than just going all tube and so I'm curious about this. Thanks!

 

[burger]

The production EJ is of course inherited from the custom amp that I did for Joe Barresi, and that one off amp has the switchable FET first stage in it. The idea behind it is to include a shaped mid boost into the front end to gain up and even further tighen up the amp in the same way you might with a pedal - however of course the high voltage MOSFET is on a 250vdc supply rather than a 9 or 18 that you might have in a pedal. More gain, more dynamic. It's a 3 stage deisgn without the F.T.G. boost engaged and 4 stages with it.

#FTG

 

[Meeotch]

Great info, so is it accurate to say an advantage of the FET boost is that it can be shaped (i.e. mid hump) vs a tube stage that can't be shaped? I understand that the high voltage circuit provides more dynamics compared to a pedal out front, just curious about advantages/disadvantages of FET vs tube.