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From: Maurice & Louise-Ann on AKAMA (no email)
Date: Fri Dec 02 2005 - 00:41:21 EST
John,
Nope, diodes will not do it. They are for DC and audio is AC. I can
think of several ways to do it, none particularly elegant. Rube Goldberg
to the rescue...!
1. Use a switch from a surplus electronics store. What you want is
four-pole double throw (better would be 5-pole so you could isolate the
grounds too but these are rare). Most of these switches are push-push
(i.e., button switches, not toggles). You probably won't find one at
radio shack, although I'd have thought that they'd have a switch box for
multiple audio sources. Did you try automotive audio specialty shops?
These days the kids put a hell of a lot of speakers in their cars; maybe
they switch some on and off?
2. Use a 12-volt relay. Relays in multiple poles are easier to find.
Again, you need four pole double throw. Put one radio on the four
normally-on contacts, each speaker on the four movable contacts, and the
car radio outputs on the normally-open contacts. If the car radio has a
switched wire (most now do for antenna activation) then use this to
power the relay, otherwise run 12-volts to a toggle switch. When the
car radio is on it will go to the speakers and the other radio will be
cut off. There is an issue of cutting speakers off of an active radio,
which might cause problems in old equipment. But modern equipment does
not care if the speakers are hooked up or not.
3. Use a four stack variable potentiometer of about zero to 10 or 50
(not critical) ohms; a shop specialising in public address systems might
have some of these. A good industrial electronics shop definitely will;
you usually buy the shaft and know assembly and add pots to it in the
desired number. You'd need a wire wound one that could handle some
power, maybe five watts or so, depending on how powerful your radios are
and how loud you run them. Put the speakers on the wipers (movable
contacts) and one radio at one end of the resistor and the other radio
at the other end. As you rotate the control, one radio will fade out
and the other will fade in. In the centre you'll hear both...might make
for some rather bizarre effects!
Since you are only switching the active line, you will just tie the
ground wires all together. Check first by running a wire from the
ground of the radio to the ground of one of the other radio speaker
channels. If there is no hum set up, you're in business...otherwise it
is back to the drawing board. With the relay or the push-button switch
you'd need only a single additional pole to switch the grounds (tie 'em
all together on each radio and on the speakers and run each of the three
resultant wires to a pole.
Good luck.
Maurice
-----Original Message-----
From: John Boy "Waka Waka Waka" [mailto:]
Sent: Friday, 02 December 2005 17:01
To:
Subject: T&T: Wiring speakers to multi amps
I want to install a 12V automotive radio/CD player, (set up for 4
speakers) in the salon and drive the 4 speakers already installed, (two
inside salon and two out on back deck) that are wired to the home
stereo reciever/amp we now have.
My concern: how can I do this without backfeeding the amp not in use and
doing harm?
I know that properly sized/ placed diodes in the 8 amp wires could, in
theroy work but I'm not savy enough to know what and how or if something
already exists for this situation.
I also know that if I could find a switch box that would handle the 8
inputs switched to the 4 outputs that would work but have been unable to
find such a unit or someone that knows of one by asking at local audio/
radio shack.
Anyone done this, or have a suggestion? Hope so....
"The winner of a Rat Race is always a Rat, the only thing I can think to
do about that--is to haul up the anchor."
- Ken Gill -
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