Plexi 6V6 With Bootstrap

[MiniVanMan]

I've built a Hoffman Plexi 6V6 and everything is running great.  I built it with the eventual intent of bootstrapping the cathode follower (i.e. The Valve Wizard bootstrap)



In my mind what I was going for would be a real-time switching between the bootstrap and normal operation via a footswitch.  However, after thinking about it, figured I'd ask how that will affect the longevity of the tube, and if it will even operate in real-time. 

By real-time, I'm really asking how long would it take for the tube to switch between normal and bootstrap modes? 

I'm surprised by the level of gain the Plexi 6V6 has in its designed state, so this is literally just an experiment.  But I don't want to go blowing tubes by switching back and forth, or doing something that isn't going to operate the way I have it in my head.   

[sluckey]

Give it a try. Might be fun. Not gonna hurt any tubes. Switching should be very fast. If you want it foot switchable, consider using a relay to keep those B+ voltages inside the amp.

[SILVERGUN]

Give it a try. Might be fun. Not gonna hurt any tubes. Switching should be very fast. If you want it foot switchable, consider using a relay to keep those B+ voltages inside the amp.

How would you feel about adding a cap in series with C1 and putting the relay switch between C1 and a newly added C2? (adjusting for series capacitance values, of course)

[MiniVanMan]

Give it a try. Might be fun. Not gonna hurt any tubes. Switching should be very fast. If you want it foot switchable, consider using a relay to keep those B+ voltages inside the amp.

Yup.  Threw a relay on there.  The outcome wasn't desirable, but it worked. 

I lost a considerable amount of output with the bootstrap engaged.  I did get more gain, but the loss of output was unacceptable.

I didn't use a capacitor in the circuit, which may help with output, but I can't imagine it would help as much as would be needed. 

Oh, and yes.  Switching was instantaneous.  But I used a mechanical relay for testing.  So, there was considerable switching noise.  That could be fixed with a MOSFET relay if I figure out the output problem.

[PRR]

...I didn't use a capacitor in the circuit, ...

Can't bootstrap worth a darn without a bootstrap cap.

Or do you mean cathode cap?

[pdf64]

…Threw a relay on there.  The outcome wasn't desirable, but it worked. 

I lost a considerable amount of output with the bootstrap engaged.  I did get more gain, but the loss of output was unacceptable.

I didn't use a capacitor in the circuit, which may help with output, but I can't imagine it would help as much as would be needed. 
…

A schematic is necessary, from the description I can’t make sense of what you’ve done.