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Since
3/23/99

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SRPP
Decoded

This
Issue

SRPP at
last

Editor,
Congratulations for your web-journal. It is
unique and a joy to "receive", every month (if the May issue is on
time, we'll forgive the April joke). ...I have not read anything
about SRPP and mu-follower (with the possible exceptions of hybrid
versions) operations. Are you planning to write something about
them? or is there some kind of aversion for these topologies, which
would be a real contradiction with the extraordinary creativity and
openness displayed throughout the Journal....
Olivier

We have been meaning to expose the inner workings of the SRPP
circuit for some time now, but we just have not got around to it.
Why? Because this circuit topology is so popular, but so little
understood, we knew that the SRPP would require a lengthy
explanation, which damped our ardor somewhat. Second, we had hoped
to get a copy of the 1943 patent for the article, but we never did.
In spite of which, here is what will surely prove to be the first of
many articles on the SRPP circuit.
Remember, if you
have a request or suggestion of your own for either an article topic
or circuit, please e-mail:

Editor

Symmetrical SRPP
and Fixed Bias SRPP

This circuit has many names: SRPP, SEPP, Totem
Pole, Mu Follower, Mu amplifier, Cascoded Cathode Follower, and its
original name, the Series-Balanced amplifier (Feb. 1943, US patent
2,310,342. Just what "SRPP" means is uncertain; maybe it stands for
Series  Regulated Push-Pull amplifier or Single-Ended
Reflexive  Push-Pull amplifier.
Wildly
popular, this circuit was the defining vacuum tube circuit of the
90's. It appeared in high-end SE amplifiers, line stages, phono
stages. Why all the fuss? This circuit promises the advantages of
both the Grounded Cathode amplifier and the Cathode Follower: high
gain and low output impedance.
Yet, in spite of its
popularity, few realize that it is not a single-ended circuit. In
fact, most tube fanciers are shocked when told that this circuit is
fundamentally a push-pull amplifier and not that radically different
than the output stage of the a push-pull power amplifier like the
Dynaco ST-70. "It must be single-ended…look there's no output
transformer!" (A quick re-read of the June
1999 article on push-pull amplifiers is encouraged.)

In This
Issue

1
17
19

SRPP Decoded
Design
Idea: A Safe Loftin-White
E-mail
Publishing
Information
Glossary
of Audio Terms
Glass-Ware.com
Articles
Classic
Magazine articles

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