DIYprojects.info

Boborann · Guest

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

Guest

I can get binaries, but I don't see a link.

I really would like to see the print for this contraption.

JURB

Boborann · Guest

Thanks for the heads up I did'nt realize that how it worked and will post to
a binaries group ( non Porno) in the future
BOb
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:4e7e59577adave@davenoise.co.uk...

Guest

Homer J Simpson wrote:

Ancient_Hacker · Guest

Okay, I understand how you could be deceived, but you're WRONG, this is
a stereo circuit.

The way it works is:

(1) The SUM of the left and right channels is amplified the usual way,
with the output tubes being driven in push-pull, but CLASS A, so the
average B+ current does not vary. That is important, as we'll see
later on..

(2) The DIFFERENCE is applied to the output tubes IN PHASE. This
signal cancels out in the main output transformer, so it doesnt bleed
into the main output signal, the SUM.

(3) The difference signal, applied to the outut tubes in phase, shows
up as current variations in the output transformer primary. That
signal is picked up by the smaller transformer that is in series with
the center tap.

So we have in effect TWO separate class A amplifiers. The transformers
do the magic of separating the in-phase and out of phase signals.

(4) Then at the secondary of the output transformers, more magic. The
secondaries are hooked up so that the difference signal gets added to
one half, mathematically (L+R) + (L-R ) gives 2L, then in the other
half, (L+R)-(L-R) gives 2R. Voila! Stereo!

Guest

Homer J Simpson wrote:

propman · Guest

meow2222@care2.com wrote in
news:1162421322.328804.255210@h48g2000cwc.googlegroups.com: