Fig 6.
In 2005 I had a job to fix
an "energy transducer" produced by James B Lansing in about 1959.
The energy
transducer was just a two channel amplifier.
It was originally full of
germanium transistors and many were fused.
I refuse to replace germanium
transistors with more of the same in any circuit unless I am bribed into doing
so with so much money that I cannot refuse. If ever there will be a bunch of
electronics that won't be missed it will be all the junk
with germanium
within which lasted on the scene between about 1954 and 1960. The resistors and
capacitors of that era also were often very poor, making all the gear with
germanium devices even less worth collecting.
The first transistors were
point contact germanium items with horrific characteristics, and makers of tubes
chuckled about then since they were such poor performers.
But production
increased and they weasled their way into countless small radios to give us
inferior sound quality
that the poor could afford and carry around in their
pockets.
The germanium power transistors were very prone to easy failure from
heat and had poor linearity
and had current leakage problems.
In about
1960, the bipolar junction transistors
were made using silicon and with a new heat process and suddenly it was all over
for vacuum tubes because the silicon was thermally more rugged than the
germanium, and perhaps even better sounding.
The current linearity of the new silicon based bjt
wonders was a lot better and leakage currents were not a problem and
soldering them was easy without having to use heat sinks clipped to the
leads while soldering.
The world suddenly got a
heck of a lot more cheap electronics, but no better musicality in
amplifiers.
The early JBL "energy
transducer" was merely a 30 watt per channel stero amp for an organ and speaker
console a guy has in
Melbourne.
I removed all the germanium
based circuitry and old R&C parts and filed them in the rubbish
bin.
The circuit I used is as
follows :-
Fig 6.
The circuit uses the
original power transformer with CT secondary to produce +/- 27V rails
with a
bridge of diodes.
The arrangement of
Q7&Q8 as darlington pairs to drive the Q9&Q10 effectively give the
output emitter followers
stage a high base input resistance because they are
effectively connected as darlington triples.
Therfore the base input
resistance to Q7 and Q8 is very high.
The gain of the VAS stage Q4&Q5 is
not disturbed by input resistance variations of the output stage.
The amp
continues to make nice organ music.
But hey, give me a Hammond with a tube
amp if you want the best sound!
Fig 7. 
I
made the perforated steel cover which slots into position at the bottom and is
firmly
held by two screws for easy access for
servicing.
Fig 8.
I fitted new RCA
inputs and level adjust pots, IEC mains input socket and fuse
holder.
Fig 9.
The vew is with all
the covers off and the amp lying
with the panel in Fig face down.
The
boards for each channel are white fibreglass with wire tracks and surface
mounted R,C, and other parts.
New PS capacitors are fitted on the right side
with a pair of fuses for the outputs in front of the
caps.
Fig 10.
With all covers
screwed into place.
The amplifier unit fits into a long speaker unit for an
organ with speakers at each end.