I haven't any background experience to make suggestions, but this perplexing
circuit you're seeing sounds a like the schematic I looked at for the
*Peavey Mace A* series (6, 6L6GC output tubes).
That's sounds like how the schematic was drawn, although I haven't see the
actual circuit layout of that model.. separate resistors were used for each
tube of one pair.. then another pair was wired direct, while the third pair
had 2 more separate resistors shown between those pairs (appearing like the
2 resistors were wired in series between those 2 pairs).

There seem to be numerous similarities in many PV amp model schematics of
the power output sections, but then some specific oddities in a couple of
models' schematics that look out of place (to me, anyway).

One thing that I have discovered recently, is that there are a huge number
of PV amp users, and lots of forum discussions about many modifications
(some that have produced results, and some that don't) and also repairs.
You're probably already aware that many forum discussions wrt electronic
circuits can include unintentional errors and/or other misleading info (this
mod I came up with is the ultimate! for example), so that much of the forum
info needs to be pondered and then either accepted or rejected by one's
better judgement and/or experience.. and compared to the rule: if it werks,
don't **** with it.

As I've only recently started dabbling in this area, I've noticed one thing
that's prevalent.. practially every component in/on guitars and amps have
been tampered with and replaced, and the majority of reports of the actors
claim that the acts produce amazing results.

--
Cheers,
WB
..............


"Arfa Daily" wrote in message
...
A muso customer has asked me to carry out some tonal mods to his Peavey
Classic 30. All pretty straightforward cap changes and so on. However, he
also asked me to look into fitting a pentode / triode switch whilst I was
at it. At first glance, this didn't look like a problem. The output stage
is a fairly classic AB class using 4 x EL84 tubes as two paralleled pairs.
Anodes of each pair commoned. Cathodes all commoned and decked. Grids of
each pair commoned via individual 47k stoppers. But then, things get a
little odd around the screen grids. One tube of each pair, has its screen
grid fed by a 100 ohm 5 watt resistor off the "screen" supply rail, whilst
the other of each pair, has its screen grid fed *direct* from the "screen"
supply rail.

I don't think I've seen this done before. I've seen one screen resistor
feeding both tubes of a pair, or one resistor per screen, but not just one
tube having a screen feed resistor. Apart from anything else, I wouldn't
normally have considered it very good design practice to have no current
limiting at all in place. Also, it will mean that the screen voltage will
be higher on one tube of the pair, than the other. I doubt that it would
have a significant effect on the operation of the stage, but just
interested as to whether anyone else has come across this configuration,
and knows the design reasoning behind it. Anyone got any opinions about
just strapping the screens to the anodes on each pair via a switch, to
implement a triode mode ?

Arfa