Need to design an A/off/B box to use one set of speakers with two stereo amps

[fatboy01]

I have two stereo amps (roughly 100watts), and I want to use one pair of Bose speakers for both.

I'd like to wire up a simple toggle switch box that will provide Amp A/ OFF/ Amp B

All wiring will be with straight speaker wire (no rcas). Can someone help me figure this out? I have figured it out using 4 DPDTs but I would rather keep it simple with just one switch.

[Brad1]

Two amps, one set of speakers.

Antique Electronic Supply

Search for #P-H521 SWITCH - CARLING, DPDT, TOGGLE, 3 POSITION, (ON-OFF-ON)

L & R speaker + and - to center lugs.

Amp A + and - to one side (On), amp B + and - to other (On), observing proper polarity.

Center-Off.

Up, Amp A.

Down, Amp B.

(Connections only made at "On" positions).

Would that work?

I think I'd still be careful to not have both amps on at once, anyway. And, I wouldn't do that with any tube amps.

Anyone?

Brad1

[Jazz P Bass]

On Off On DPDT

Sounds good to me.
I think they even have these at Radio Shack.

I hope the audiphiles don't hear about this.
"You sent an audio signal across a switch contact. Eewwhh!"

[oc disorder]

One switch for the left and one for the right.
Preferable to do the switching when no audio is passing through.
Hi-Fi shops have "comparators" fancy name for bunch of switches to do that.

As a side issue I recall the UK bank Rockpile (late 70's) had a marshall combo and a head assembled in a flight case rigged up with a footswitch connected to a relay so the combos speakers could be switched to either amp.
I thought that was a good idea as you could tweak one amp for a good solo sound and the other for rhythm.Must have had some loading resistors in there somewhere ..the input was probably switched as well but I cannot recall.
Glad I didnt have to carry it... was like a small wardrobe !

[fatboy01]

Thanks for the reply. I had figured on wiring it up that way because simple is the goal here, but wouldn't I be loosing the stereo and converting my signal to mono? I had looked at 4 pole rotary switches, but I don't think they could handle the wattage.

This switch is for my gf's mother, which is why I want to keep it simple. One amp is a traditional solid state stereo receiver, and the other is a modern low watt ipod reciever (which came with low end speakers).

It seems a rugged DPDT toggle is the best and most user friendly way to go. Do you feel there will be a noticable difference in SQ if I wire it up as posted above?

Thanks again Brad1

[Brad1]

... but wouldn't I be loosing the stereo and converting my signal to mono?

One amp is a traditional solid state stereo receiver, and the other is a modern low watt ipod reciever (which came with low end speakers).

Do you feel there will be a noticable difference in SQ if I wire it up as posted above?

First answer: Not quite, but I was wrong that one switch would do it, actually, the way I described. You'd actually need a triple-pole, double throw "on-off-on" switch to do both channels. (Left, Right, with negatives both connected to center row).

You MAY be able to do this with one DPDT switch anyway. You'd just connect the negatives of the speakers, and the two amps together in one point. (Ground is ground , right? Well..more on that later).

Connect the L & R positives (left and right speaker positives) to the two center lugs.

Connect left-channel/right channel positives of each amp to the lugs on the ends of the switch, each amp to opposite ends, keeping left and right respective in the path.

And it may look something like this:

Negative left and right speakers connected to amp A and amp B left and right negative channels. (Four wires connected permanently)

+++++++++Amp A right channel (Switched "Up")
Positive right speaker center lug, right side (Center "Off")
+++++++++Amp B right channel (Switched "Down")


+++++++++Amp A left channel (Switched "Up")
Positive left speaker center lug, left side (Center "Off")
+++++++++Amp B left channel (Switched "Down")


One thing that MAY be a concern ( the "more later" thing) is potential ground differential problems that may show up as excessive hum, because the speaker grounds of both amps are connected together. Otherwise, the two positives of each amp are isolated from each other, and from the other amp's positives, through the switch.

Second statement: Lo-watt iPod thing is probably woefully inadequate to drive a pair of Bose, anyway. If it's some little docking-station thing with a miniscule amp output, any semblence of whatever quality left in an MP3 is going to get mangled cranking the thing to get any volume at all through those Bose speakers. That thing doesn't have some kind of a line out that you can connect to the other receiver's line-in, somehow? What kind of "iPod" receiver is it? Make, model? Maybe there's a better, cheaper, easier way to play already compromised-sound-quality music through? It may not be any worse-or better-than just plugging an 1/8" stereo-to-RCA L/R cable into some line inputs on the receiver, and adjusting the iPod volume to those inputs for the best (least worst) usable level.

Doing this all in my head, so correct me if I'm wrong.

Brad1

[fatboy01]

The 3PDT switch is a good idea, I'll shop around for a hefty one. What minimum ratings should I look for?

The ipod player is a Sony Micro HiFi Shelf System. I just pulled up the specs and its 25w RMS per channel. It only has analog outputs (speaker wire connections)

[fatboy01]

I would just buy an ipod-RCA cable and plug striaght into the main amp, but the Sony was a gift and she would like to use both.

[kepeb]

you can get 4 pole double throw, they are more expensive but if you only need one...

i think i would settle for two dpdt's one for each channel doubling what BRAD1 said first. i think that would be the simplest, cheapest way.

i've been looking at this same thing but with connectors because i want to hook up 3 different sets of passive speakers for monitoring.
i wanted the option to swap and change later so connectors would be ok.
although the red and black plastic spring grip connectors are cheap. using some of these with dpdt's you can make pretty much any arrangement.