On Sat, 28 Oct 2006 09:25:31 +0100, "Dave Plowman (News)"
wrote:

Thought this might intrigue...

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From: Boborann
Subject: a single output transformerstereo tube amp ??
Date: Sat, 28 Oct 2006 01:30
Newsgroups: sci.electronics.repair

I bought a Columbia680 stereo today on Craigs list which I assumed was mono
as it had one output transformer and a pair of 6L6's and a mono tuner input
When I tore it down and found the schematic I found that it was in fact
stereo and used a single 6L6 for each channel and they shared an output
transformer .
What looked like a traditional Push Pull design is actually fed with a
channel per 6L6 and in phase .
The output winding is Center tapped and has a speaker attached to each side
of the winding.
Curious whather anyone has ever seen this and could comment on how common
it was

Thanks
Bob

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Obviously designed by a telephone engineer, because that is exactly
how the hybrid transformer in a phone works, allowing a separate
signal each way on the wire.

I shudder to think what the sound is like though, because you can only
maintain the necessary balance over a very limited frequency range. I
wonder what exactly it was designed for...

d

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http://www.pearce.uk.com