The 1937 Speech Amplifier
This speech amp has three inputs, two can be seen on the front.
on the left is for a high-Z mic. The center jack and one
on the rear apron
are for high level, low-Z balanced sources.
For the mic input, the tube line-up is a type 57, a 2A6, then to
a pair of 56's for
the output. All inter-stages and the output are transformer
coupled with UTC's.
The line level inputs bypass the 57 and are transformer coupled
to a separate
2A6 for each input.
Remarkably, this amp worked without anything being replaced, even
supply filter caps. It is still working now and I have been
using it on my BC-610
with very good reports.
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