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Max Holubitsky
 
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Do not put amplifier outputs in parallel. This has nothing
to do with O/P transformers. Any decent amplifier has a
very low Thevenin equivalent generator output impedance,
well below one ohm, likely around 0.1 ohm. BTW, this has
nothing to do with the nominal 8 ohm speaker rating which is
a measure of the ability of the amplifier to deliver
current. Thus, if the individual outputs are in any way
different the difference signal would see this load , i.e.
the other amplifier, and a huge current would flow that
could cause damage. Just being "in phase" is no guarantee
of no difference signal, e.g. the gains could be different.


I find it hard to believe that any tube amplifier designed for guitar use will
have such a low output impedance. I know what you are saying, and it is 100% true
for a solid state amplifier, especially one with a large dampting factor, however,
the amplifier in question will likely be just fine. I doubt that a tube guitar
amplifier will have a better damping factor than, say, a Dynaco ST-70, and the
Dynaco is intended to be paralleled this way.



The correct way to get double the power is to bridge them
(see elsewhere) or much better, IMO, use two speakers - they
can even be in the same box.


Agreed 100%



Cheers,

Roger

--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada.

"Friends don't let friends vote Liberal"