In article , Eiron
wrote:
[snip]

This is all the info I can find on the web:

"Basically it's a complementary common base amplifier with only two
transistors: BC485 and BC486. The collectors are connected together and
the input goes to the emitters through 2200uF capacitors. The bases are
grounded. The output is taken from the collectors through a 22uF
tantalum cap."

There are some datasheets, e.g.
http://img.aussieaudiomart.com/uploa...stepup-amp.jpg

And someone had to replace his dried-out electrolytics.

Thanks. :-) That supports my recollection, but I'd still really like the
diagram, ideally as once provided by Ortofon.[1] That would help me explain
the changes I made for my 'improved' version. Ideally, I'd love to be able
to show the circuits side-by-side when explaining why the reviewer was
shooting himself in the foot. :-)

FWIW If you look at http://www.audiomisc.co.uk/Armstrong/700/730circuit.gif
(top left of diagram) you can see what I did. The MCA-10 only had a pair of
+/- 1.5-ish volts dry cells as its PSU. I had a decent PSU so could provide
a bit more 'room' to give the transistors a better working environment.
Lowered the distortion and increased the headroom.

Jim

[1] That said, I may well have opened the box and worked out the Ortofon
circuit at the time! Alas, the relevant notes seem to have long gone, now.
I keep looking though. A bit like the cat in "The door into summer". 8-]

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