On Sat, 03 Mar 2007 21:28:45 GMT, "Ian Iveson"
wrote:

Jim and Don continued:

I think the interstage transformer is just the way phase splitting
was
done when transistor amps used a pair of PNP output transistors and
an
output transformer.

Yes. IIRC Various makers produced designs like that in the early/mid
1960's. Partly for the reason you give, but I suspect also because
the
designers in those days tended to be accustomed to the idea of
including
signal transformers in amplifiers.


It makes for very simple, if not terribly linear, biasing of the
output
pair.

IIRC There were also problems due to the phase shifts introduced by
including a transformer.

I see.

So, rather than being like a valve amplifier, it is a typical early
transistor amp?

Which was pretty much like a valve amp, because they were all we had
been designing up to then.

Now you can continue to wonder why it sounds good.

Remember we are talking good in the context of a guitar amp. Hi Fi it
ain't.

I guess a layout can be misleading. It looks like the circuit is
symmetrical before the interstage. It would be interesting to know the
winding ratios of the transformers.


Probably not far off 1:1. These transformers aren't transforming huge
impedance differences the way they do with valves. They are just there
to mess up the sound slightly.

d

--
Pearce Consulting
http://www.pearce.uk.com