Good Way to Shut Down 2 of 4 Output Tubes?

[The New Steve H]

Is there a good way to kill half of the output of a 4-tube push-pull amp? In other words, if you have 4 output tubes, is there a good way to shut two of them down without messing up the rest of the circuit?

Is it possible to simply disconnect the plates from the B+?

The Herzog thing I built has a neat muting circuit that shoots negative voltage to the control grid of the output tube.

Putting up a schematic of a 135-watt Bassman with 4 output tubes. I am not planning to build this, but it shows the kind of output section I'm talking about.

[martin manning]

The easiest, and lowest-voltage way is to lift the cathode grounds of one tube on each side, and double the load impedance.

[The New Steve H]

I guess shutting off the B+ would affect sag and sustain on the remaining tubes, right?

[The New Steve H]

Maybe there is no point in doing this. It seemed like an interesting idea.

I didn't think about the difference in current draw. I think you're going to get that no matter how you shut down the tubes, so surely you would get a change in sound. Maybe the only way to do it right is to have two separate power supplies for the tube banks? That would be a real rat's nest of components and wire.

[Gibsonman63]

Normally you wouldn't need to shut off two tubes on the fly. Just pull two power tubes. It will change your output inpedence, but most amps don't seem to care.

[Reeltarded]

Honestly, why half power is even considered perplexes me.

There is hardly a difference in 5 vs 10, or 50 vs 100. It just sounds a bit different, ie; not as good, of course in my opinion. Ya know.

The difference between 50 and 100 is not even a lead boost in many situations, and if it's too loud @ 100, 50 isn't going to impress the angry ears.

[The New Steve H]

I think you're right. I was just fiddling with the notion of finding a way to take advantage of a PT that was oversized.

[Zippy]

I think you're right. I was just fiddling with the notion of finding a way to take advantage of a PT that was oversized.

So you want to wire it for 4 tubes only to turn 2 of them off???

Just use the tranny and wire it for two tubes. Consider it "conservatively designed".

[The New Steve H]

I was thinking of doing that, but you know, all that juice is sitting there waiting to be used for something...

I think I'm just going to use the 18W Marshall PT Tubeswell suggested.

[Zippy]

I was thinking of doing that, but you know, all that juice is sitting there waiting to be used for something...

Dude. Stereo. It's the future...

[Gibsonman63]

An all tube JC120? How awesome would that be?

[Zippy]

Could it be any heavier?