nice looking amp was originally thought as additional amp for radio consoles
when stereo sound came up.
was designed for 5 Ohms and delivers (using new tubes) 2 watts to 4Ohm and
1.5 watts to 8 Ohm loads.
As it only had to reproduce higher frequencies,
the frequency range was cut in the higher bass range by using very small
coupling caps (220pF). At the same time a small cap from the plate of the
input triode was used to avoid self excitation, but the result was an
unsatisfying high frequency response for HiFi use.
Some later amps (S82)
have different speaker jacks (DIN).
The precurser to the
S81 - the S81 - is also found with different output transformers.
See below what you
should do make a high fidelity amp of this unit.