How to do A/B/C speaker switching from single tube amp head?

[Michael7]

You guys are putting the fear in me that solid state and tube amps might behave differently hooked up to such a device and I don't know if I want to have to remember to treat them differently. Unlike a rotary switch which connects to one speaker at a time, these push button boxes allow more than one to be pressed at a time. I could forget to press only one and possibly have a problem. Maybe I should just go back to basics, turning off my amp for an instant and then changing the cable to the next speaker cabinet.

 

[Raabje]

You guys are putting the fear in me that solid state and tube amps might behave differently hooked up to such a device and I don't know if I want to have to remember to treat them differently. Unlike a rotary switch which connects to one speaker at a time, these push button boxes allow more than one to be pressed at a time. I could forget to press only one and possibly have a problem. Maybe I should just go back to basics, turning off my amp for an instant and then changing the cable to the next speaker cabinet.

Well, as stated by some of us, turning the master volume down of the amp head, and hot switch the speaker cabinet, will also not harm your tube amp.

I guess when you are playing on stage on full volume, and your speaker cabinet stops working because of malfunction, then the power transformer maybe get destroyed because you are playing through before you notice.

 

[Michael7]

The point I was making is that if I have to go to the amp to do any knob adjustment down and back up, it is just as easy to switch it completely off and move the speaker cable to the next cabinet I want to try and then turn back on.

 

[Raabje]

Aha, that wasn't clear to me. But I think you have to turn knobs on the amp anyway after a cabinet or speaker swap, because volume is different, or tone, or gain. You have to adjust a few little things to make it sound right again.

 

[gcvsa]

Do NOT use a speaker selector designed for architectural or home audio for switching tube guitar amps, unless you want to make a very expensive mistake.

Speaker switchers for tube amps are expensive, because they have to be.

A transformer coupled tube amp MUST have a load attached at all times while the amp is in operation. If you don't understand why higher impedances are bad, then you should look up "flyback voltage".

A transformerless solid state amp can be run into an open circuit (infinite resistance/impedance), but will be destroyed running into a dead short (zero resistance/impedance).

So, in building a switcher capable of handling tube amps, you are dealing with medium to high voltages (much greater than 2 V p-p) and you have to be sure no tube amp connected to it ever has too high of an impedance attached to it.

Most tube amps can handle a mismatch within reason (double or half the nominal rating), and that is why you can build a switcher with internal dummy loads and "make before break" switches.

A 100 W RMS signal into 8 ohms impedance will produce about 28.28 V RMS, or about 80 V p-p.

 

[DougMen]

Do NOT use a speaker selector designed for architectural or home audio for switching tube guitar amps, unless you want to make a very expensive mistake.

Speaker switchers for tube amps are expensive, because they have to be.

A transformer coupled tube amp MUST have a load attached at all times while the amp is in operation. If you don't understand why higher impedances are bad, then you should look up "flyback voltage".

A transformerless solid state amp can be run into an open circuit (infinite resistance/impedance), but will be destroyed running into a dead short (zero resistance/impedance).

So, in building a switcher capable of handling tube amps, you are dealing with medium to high voltages (much greater than 2 V p-p) and you have to be sure no tube amp connected to it ever has too high of an impedance attached to it.

Most tube amps can handle a mismatch within reason (double or half the nominal rating), and that is why you can build a switcher with internal dummy loads and "make before break" switches.

A 100 W RMS signal into 8 ohms impedance will produce about 28.28 V RMS, or about 80 V p-p.

That is precisely why I recommended the switchers from De Lisle guitars, because they are made to use with guitar amps, but he didn't want to spend that much, so I then told him he could use the stereo style switchers at his own risk. He doesn't plan on using it with high power amps, only 15W amps, and only to switch between cabs with a single amp, so the amp will never be operating without a load.

 

[Stringbender53]

I'd suggest checking both Radial Engineering/Canada and Lehle/Germany product lines as I believe both make switching devices for one head switching to different speaker cabs and guitar signal switching to multiple heads/cabs. Their stuffs not cheap but is engineered to keep from smoking expensive gear safely and quietly. If your not an electrical engineer or designer don't try and second guess what all's involved 'cause it ain't worth the time, trouble, and anguish it can cause.

 

[DougMen]

I'd suggest checking both Radial Engineering/Canada and Lehle/Germany product lines as I believe both make switching devices for one head switching to different speaker cabs and guitar signal switching to multiple heads/cabs. Their stuffs not cheap but is engineered to keep from smoking expensive gear safely and quietly. If your not an electrical engineer or designer don't try and second guess what all's involved 'cause it ain't worth the time, trouble, and anguish it can cause.

Radial's Cabbone ones for amp/cab switching are all discontinued. For simple guitar/amp switching, any basic switchbox will do. The De Lisle ones I linked to are very good quality and the least expensive that I can find. The Swiss company KEH makes very high quality ones too, but they're very expensive, with the least expensive being $749. The least expensive De Lisle is $199, and can do one amp/3 cabs, or one cab/3 amps, as it has dummy loads inside it to protect all amps.