Amps, Speakers, & Zoning

["Paul Gordon" <paul_gordon@xxxxxxx>]

Morning all!

My good lady has insisted that I put some zoning in place for our Homeseer
announcement speakers. Currently, I have an old amp connected to the PC
soundcard (mainly becuase it drives two pairs of speakers - the PC
soundcard
is one of the motherborad built-in ones, and it only has a single
line-out).
To which I have currently connected a single pair of speakers, - one in the
living room, and one in the bedroom. (I don't need a stereo pair for simple
TTS announcements)

- which reminds me of a funny story! - the wife was NONE too impressed when
the "Genie" agent character started heavy breathing from the
corner of our
bedroom!!!

My plan was to have simple zoning (two zones) by using the amp's A - B
speaker selection. - However, the amp does not have IR control (it's circa
1979 - the first bit of HiFi kit I ever bought, and it's still going
strong!), so I had hoped to open up the case and replace the physical
pushbutton speaker select switches with a couple of relays. Unfortunately,
having had a look inside, I don't think I'll bother!! - access is extremely
difficult, and I would have to completely disassemble it to get to the back
of them - including taking out all that "string" that moves the
tuner!! (I'd
never get that back in properly!)

So, I need to put in some way of zoning these speakers (and some more),
that
is external to the Amp, and controllable by Homeseer. My initial thoughts
are:

Some cordless RF speakers from Maplins. - TXmitter on the Amp, individual
RF
speakers placed 1 per zone. These run on mains, so an appliance module on
each speaker gives HS the individual speaker control.

or,

Some relays and powerflash modules to switch individual speakers in/out of
circuit.

Pro's & con's = RF stuff is easy, but expensive, each RF speaker costs
)IIRC) £60.  Relay method is cheap, but is a little more difficult to get
right..

My question is about switching speakers in & out of circuit by relays,
and
the implication of this for the amplifier. I know that you're not supposed
to run the amplifier without speakers connected, not supposed to
(dis)connect speakers whilst the amp is on, not supposed to run with only
one speaker connected when there should be a pair etc.. etc..
(basically, amps aren't built for this are they?)

So, what must I do to protect the amp whilst still being able to switch
speakers in/out willy nilly?  How best should I go about this? What are the
implications if I run the amp with "incorrect" speaker loads (0,
1, 2, 3, or
4 speakers)?

I thought about getting one of those speaker selector boxes from Maplins,
but at £20, I thought it must be possible to DIY it with some relays? - I
don't need HiFi - it's only for TTS announcements...

Cheers chaps.

Paul G.



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