162. High-quality audio output
     ~~~~~~~~~~~~~~~~~~~~~~~~~
If you want to feed audio from a BBC B into an external amplifier, you can
use the loudspeaker output, but there is a better-quality output available.
Locate the point where the purple -5v supply wire from the front right of the
PSU connects to the circuit board, and then look slightly nearer the front,
just underneath the rear edge of the keyboard. You should find two solder
pads marked "PL16"; the rear (North) pad is Ground (0v), and the front
(South) pad is the output. This output is connected to the input of the
internal volume control "VR1", and is at a level suitable for feeding into a
hi-fi amplifier. There is a similar output marked on the BBC B+ circuit
diagram as "S21", and apart from surmising that it will be close to the
internal volume control "VR2", I have no other details.