RE: Whole house audio

["Brown, Andy [Infrastructure]" <andyb@xxxxxxx>]

Thanks for replying Nigel, I thought I'd been ignored on this one and gave
up ;)

I removed the switch box from the equation and now all is well.  The box in
question had five push button switches on the front.

I'm probably not going to bother plumbing it back in.

Cheers

Andy



-----Original Message-----
From: Nigel Orr [mailto:Nigel.Orr@xxxxxxx]
Sent: 26 September 2000 10:19
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Whole house audio


At 11:57 11/09/00 +0100, you wrote:
>I plumbed in the four new speakers into a Maplin speaker switch box
taking
>the output from the amp's speaker B sockets.

Which box?  Is it the one with a big rocker switch on a sloping front, and
lots of terminals at the back?  If so, have a look inside, I came across a
few of them with wobbly connections a year or two back, which could upset
some amps (though would be more likely to just not work at all or work
intermittently).  If it is that type, they actually do the switching by
connecting the 2 speakers in series, and the switch shorts out the speaker
that you don't want to hear.

That means that with 8 ohm speakers, the amp will either see an 8 ohm or 16
ohm load, which should keep it happy!  If it's another type of switch box,
it might have the speakers in parallel, so the amp will see an 8 ohm or 4
ohm load, the 4 ohm load might make it unhappy...

>The amp's self protection kicks in when the volume reaches a certain
point
>(and not that loud either).  It's actually quite neat - it flashes
"PROTECT"
>on the display!

Typical loud listening levels are under 10W, so as you guessed, it
shouldn't be falling over!

>Can anyone offer any advice on how to get round this?  Replace speakers
with
>16ohm versions? Solder on additional resisters?  Build something
involving
a
>transformer?

How do you have the speakers connected at present?  If you disconnect 2 of
them, does it all work normally?  Does the amp have a rating on the back
for impedance range?  Do you have your 'normal' speakers connected to the A
output at the same time, and does it work if you switch the A output off?

Nigel





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