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Author Topic: Speaker switching  (Read 302 times)

Psc

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Speaker switching
« on: July 03, 2020, 07:09:54 PM »
Hello all.  Hopefully this is the right place to ask this.  I have two solid state stereo chorus amps, a peavey stereo chorus and a jc120, and I had a thought to use them both with the same speaker cabinet and make a foot switch so I could do it on the fly.  I came up with a schematic that involves six relays. It works very much like a reversing starter.  You push the button for the peavey, it seals in a relay that closes the contacts for the speaker output for that amp and disables the jc120 relay.  To change you hit a stop button, then hit the jc120 button.

I want to do all that to prevent the outputs of the amps from connecting.  I am wondering if this is safe, and more importantly is there anything I haven't thought of.  I expect I'll need three separate plates to mount the jacks, one for each amp and one for the output so that the negatives won't be connected?

If there's a reason I should abandon this please let me know. It's one of those things that I couldn't stop thinking about.

Enzo

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Re: Speaker switching
« Reply #1 on: July 03, 2020, 08:57:34 PM »
It shouldn't matter if either amp sits unloaded, so how about one DPDT relay per speaker?  Or for that matter a single 4PDT.

The commons go to the speaker terminals, then the throws go to jacks from either amp.

My personal view: seems kinda hard core to switch between those two amps in the middle of a song.

Psc

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Re: Speaker switching
« Reply #2 on: July 03, 2020, 09:47:26 PM »
It's probably unnecessary, it's true, but I have most of the stuff on hand. So I have it set up to switch the positive and the negative, but I probably have to keep the rings separate from each amp, do I not? I would imagine you need to keep each power supply isolated.

Enzo

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Re: Speaker switching
« Reply #3 on: July 03, 2020, 10:42:28 PM »
For that matter, using the existing speakers in those two combos, a readily available ABY switch on the front end would work too, wouldn't it?

You are right, we need to isolate the speaker grounds.  The Peavey speaker return is NOT to ground, it has a current sense resistor there.  I don't have JC120 handy, but the similar JC77 does reference speakers to ground.  But still, even if both went to ground we might create a ground loop if connecting them.


When you described the project, I immediately got a mental picture of how I would do it, your inner vision is diffrent, but I bet yours will work too, and if it differs by one relay, so what.   I have a very lengthy history in relay systems - think old pinball machines and other control systems - and I think certain ways, but it ain't rocket surgery.

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Re: Speaker switching
« Reply #4 on: July 03, 2020, 11:11:55 PM »
I wasn't going to do aby because I'm making them into heads.  I should have clarified that. What I was thinking was more like having my clean effects y off to the jc120, then all dirt pedals to the peavey. I just want one 212 cabinet for the whole affair though.