Univox U-1061 - explain this output stage?

[kelly votrenom]

Simple question - could someone explain the thinking behind this circuit? It just looks to me like an engineer mis-copied some other amp design.

My intention is to parallel the plates and put in separate screen and grid resistors unless someone can explain the benefit of this circuit as designed.

Here is a link - http://4tubes.com/SCHEMATICS/Music-a...ivox/u1061.gif

or a pdf is attached.

Thanks

[The Dude]

Welcome to the place!

The plate to plate and grid to grid resistors are just there to limit tube interaction. I don't see any reason to redesign the amp, but it'll work either way. The screen grid feed is from the lower half of the totem pole. That's why they didn't use screen resistors.

[kelly votrenom]

Welcome to the place!

The plate to plate and grid to grid resistors are just there to limit tube interaction. I don't see any reason to redesign the amp, but it'll work either way. The screen grid feed is from the lower half of the totem pole. That's why they didn't use screen resistors.

Thanks for your reply & the welcome. I'm sure I'll be back often

I have never heard of wanting to limit tube interaction before (but my arena is only guitar and bass amps - maybe it's more of a hifi thing?) so if you could explain it a little more or point me to somewhere I could do some research I'd appreciate it.

I would think that the grid resistor would attach before the grid of both tubes instead of in-between to actually make the pair behave more as a single tube. And the 100 ohm power resistors (which seem to have failed multiple times in this amp) would cause one pair of tubes to work slightly harder since more current would run thru one pair.

Also, I can see skipping screen resistors since this amp has a choke which I didn't notice at first glance.

Thanks