Re: Question about amplifiers in shed

["Alan Ainslie" <alan.ainslie@xxxxxxxxxxx>]

Couple of important points.

1. If driving the line inputs of a second amp in the shed, then the main
amplifier MUST NOT be of the type which has a bridge output configuration
as
this will be damaged if the two BLACK speaker leads are connected together
as will be the case when connecting to the line inputs of another amplifier
.

(To check turn the amp off and connect a ohmmeter capable of reading low
resistance between the two BLACK speaker wire and ensure that resistance
between is very low, les than 1 ohm.  Or if no meter available, connect a
loudspeaker between the two BLACK speaker outputs when  playing stereo, not
mono, music and listen to the speaker.  There should be no output at all.
Any output from the speaker indicates a bridged amplifier)

2.    Input attenuator will be a good idea for the shed amplifier.  Simply
arranged with 4 resistors.  If you use a 10 ohm and 1 ohm resistor in
series
on each channel with the 1 ohm going to the black speaker connection then
the audio input to the second amp is taken from the one ohm resistors.
Wirewounds of rating to match the main amp, simply assembled on a chocolate
block.  email for any clarification.


There is no getting away from the fact that to do this properly the fed
should be isolated by transformer: standard practice in the good old days,
but not so common now given the cost of decent audio transformers.

Assuming that you are feeding speaker level outputs to your shed you
could just feed the outdoor speakers in parallel, making sure that the
total parallel load is suitable for the amplifier. If you want to use
another amplifier you would need to attenuate the speaker level feeds
to line level - speaker signals will be of the order of 10V line
inputs are usually about 0.2V. The quality won't be perfect, but
that's probably not a problem for garden speakers.