Speaker Switching - bright idea?

Kiwiburger · 16th December 2006, 11:09 AM

I went looking for speaker switching boxes, for routing the output of a stereo power amp to various monitors and instrument speaker cabs.

Most of the ones I found were pathetic - the size of cable you could fit was so small. And I don't necessarily want to switch pairs - this is for guitar and synth reamping duties, where I might want to mix them up.

I decided to build my own, and went looking at switches, and then I had a bright idea ... (somebody shot this down in flames if i'm wrong) ...

I think I will get some AC wall switches - the type used for wiring up house power and lighting. They can accept bigger wire diameter, and obviously can handle the current and voltage. Seems to me that if the power entering a power amp needs good sized wire and switches, the power coming out should use the same.

I'm thinking they will be so much easier to work with - no connectors or soldering, just screw the speaker cables right into the switches and have some grommets on the box. I believe I can get them in DPDT, so no grounding issues or anything.

Has anyone tried this?

The Byre · 16th December 2006, 11:31 AM

Normally, one does not switch the OUTPUT of an amp, because suddenly changing the output load of a powerful amp from inductive to zero and then back to a different inductive load can damage the output transistors.

The switches you looked at were, in all probability, designed either for very small amps or for the output from the preamp to the main power amp.

Of course, if you can wire them up so that the amp can only be switched when the power is off, then it will be OK, though switching power amps on and off freaquently is also not such a good idea.

Jim Williams · 16th December 2006, 04:16 PM

Reminds me of the time I was working on Peter Frampton's Amek Angela in NoHo. He had this problem of all the auxes leaking into the tracks on the meterbridge when the audio was turned up. It was a tech that wired up a 3 switch panel in the patch bay which switched the power amp outputs to different sets of speakers. There was leakage going on that went away when I removed the panel from the patch bay and all the line level cables.

I still remember the big smile on his face when that problem went away.

Jim Williams
Audio Upgrades

Sounds Great · 16th December 2006, 04:19 PM

Quote:

Originally Posted by Kiwiburger

I think I will get some AC wall switches - the type used for wiring up house power and lighting. They can accept bigger wire diameter, and obviously can handle the current and voltage.

That should work fine. Just make sure you get the $500 hospital grade variety.

Sounds Great · 16th December 2006, 04:22 PM

Quote:

Originally Posted by The Byre

Normally, one does not switch the OUTPUT of an amp, because suddenly changing the output load of a powerful amp from inductive to zero and then back to a different inductive load can damage the output transistors.

I've done this for years, shouldn't be a problem. You really don't have to turn the amp off in-between. As long as there is no input going on while you switch them I don't think it is an issue.

Kiwiburger · 16th December 2006, 10:13 PM

Thanks for the input - some thoughts there I would never have considered.

This is really just to save manually pulling speaker connectors in and out - I don't see a problem. I don't think leakage can be a problem, as I'll keep these speaker cables well away from line or mic cables. Mainly under-carpet wiring.

My amp has full short-circuit and open-circuit protection, and I often use just one side, with no speaker connected to the other, for guitar or bass preamp monitoring.

The only problem I can see is if I parallel up too many speakers and drop the impedance too low. I was thinking of DPDT switches to avoid this, so I could only toggle between two cabs

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16th December 2006, 11:09 AM	#1
Kiwiburger Lives for gear Join Date: Feb 2006 Posts: 3,647	Speaker Switching - bright idea? I went looking for speaker switching boxes, for routing the output of a stereo power amp to various monitors and instrument speaker cabs. Most of the ones I found were pathetic - the size of cable you could fit was so small. And I don't necessarily want to switch pairs - this is for guitar and synth reamping duties, where I might want to mix them up. I decided to build my own, and went looking at switches, and then I had a bright idea ... (somebody shot this down in flames if i'm wrong) ... I think I will get some AC wall switches - the type used for wiring up house power and lighting. They can accept bigger wire diameter, and obviously can handle the current and voltage. Seems to me that if the power entering a power amp needs good sized wire and switches, the power coming out should use the same. I'm thinking they will be so much easier to work with - no connectors or soldering, just screw the speaker cables right into the switches and have some grommets on the box. I believe I can get them in DPDT, so no grounding issues or anything. Has anyone tried this?

16th December 2006, 11:31 AM	#2
The Byre Lives for gear Join Date: Jan 2004 Location: Highlands of Scotland Posts: 1,053	Normally, one does not switch the OUTPUT of an amp, because suddenly changing the output load of a powerful amp from inductive to zero and then back to a different inductive load can damage the output transistors. The switches you looked at were, in all probability, designed either for very small amps or for the output from the preamp to the main power amp. Of course, if you can wire them up so that the amp can only be switched when the power is off, then it will be OK, though switching power amps on and off freaquently is also not such a good idea. __________________ http://www.the-byre.com

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16th December 2006, 04:16 PM	#3
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 3,946	Reminds me of the time I was working on Peter Frampton's Amek Angela in NoHo. He had this problem of all the auxes leaking into the tracks on the meterbridge when the audio was turned up. It was a tech that wired up a 3 switch panel in the patch bay which switched the power amp outputs to different sets of speakers. There was leakage going on that went away when I removed the panel from the patch bay and all the line level cables. I still remember the big smile on his face when that problem went away. Jim Williams Audio Upgrades

16th December 2006, 10:13 PM	#6
Kiwiburger Lives for gear Join Date: Feb 2006 Posts: 3,647	Thanks for the input - some thoughts there I would never have considered. This is really just to save manually pulling speaker connectors in and out - I don't see a problem. I don't think leakage can be a problem, as I'll keep these speaker cables well away from line or mic cables. Mainly under-carpet wiring. My amp has full short-circuit and open-circuit protection, and I often use just one side, with no speaker connected to the other, for guitar or bass preamp monitoring. The only problem I can see is if I parallel up too many speakers and drop the impedance too low. I was thinking of DPDT switches to avoid this, so I could only toggle between two cabs