Uneven resistance on plate

[überfuzz]

I've seen a couple of schematics that had resistors on one plate in each pair in a quad power stage. (I think it was some Marshall amps.) What is the point? Is it to prevent some sort of oscillation..? Just curious, if anyone would chime a little wisdom here...

[Jazz P Bass]

Can you provide an example.
That makes no sense.
How can the current be shared , being in parallel, if there is a resistor on one tube of the pair?
FYI: I looked at every Marshall schematic that I have.
None have a resistor on the plates of the output tubes.
Excepting the 200 watt Major.
In that case all four KT88's had a 100 ohm resistor on the plates.

[g1]

Did you mean the power tube grids?

[überfuzz]

Eh ok, scrap the Marshall stuff I wrote. I had to search for schematics with this feature... Here's one.

[g1]

I don't see any resistors connected to the plates. Grid and screen resistors are the same for push & pull. Please specify the component numbers you mean.

[Jazz P Bass]

I don't see it.
Other than the spike suppression diodes, it's a clear connection from tube plate to tube plate/ pair.

[markr14850]

I think the issue is with the screen resistors on only 2 of the 4 tubes.

[sgelectric]

I had this question with a Traynor YGL-3 Mark III. This amp also has a quad of power tubes.

Enzo provided the answer:

"Provides some isolation between the tubes.It prevents the screens from interacting"

http://www.webphix.com/schematic%20h...ii_ygl3_3a.pdf

[diagrammatiks]

those are the screen resistors.

Normally you'd want 1 per tube.

they used one per push/pull pair.

profit - trillions!

[g1]

Thanks Markr, now I see it, 2 screens with screen resistors, 2 screens straight to the screen supply.

[kleuck]

The point is, i think, to mix two different compressions curves >> "richer sound"