Re: PP Amp driven SE

In article <4401D7A4.49C8AB63@xxxxxxxxxxxx>, jh.stewart@xxxxxxxxxxxx wrote:

Back a few months ago there was a thread wherein folks were discussing
various schemes to drive a PP Amp without a phase inverter or an
Interstage Transformer.
Some suggested the LTP in the power stage.

I've been on the run since so not sure where the whole business went.
Anyway, over at ABPR is a circuit that may have been suggested, so if it
was then my apologies to whoever came up with it.

In this case the power OP LTP is sinked thru a choke rather than
resistors or an active device. That results in a large power saving &
considerable simplification of the circuit. As shown the circuit is NOT
optimized & appears for reference only.

The choke & OPT are in the Hammond Catalogue as their 125E & 157G. The
schema show results with & without the choke in the circuit. The balance
of AC plate currents is very good down to about 20 Hz. The circuits show
resulting currents with & without the choke in the circuit.

Hi John,

Your scheme requires a large audio choke that can handle a substantial DC
current without saturating. An equally simple scheme would be to use a
high inductance center tapped audio choke in the grid circuit, with the
center tap grounded and one end connected to the driven output tube grid
and the other end connected to the grid of the second output tube. This
scheme also halves the required drive voltage relative to the cathode
choke scheme. General Motors here in the US used the tapped inductor
scheme in some of their tube auto radios.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/
.

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