Stereo Guitar Cabinet Switcher

Stereo Switcher Instructions

I want to build this thing but I am still unclear as to what I will use and how I will use it. I had asked earlier about the DPDT relay being used for stereo pairs of speakers (I am dense..but willing to learn)? If someone could recommend some parts and maybe a schematic?

I will want to build this thing as a rackmount gizmo and I will use the midi-preamp which has a switch control thingie (latch/unlatch) to activate it.

GtarPlaya11 said:

I want to build this thing but I am still unclear as to what I will use and how I will use it. I had asked earlier about the DPDT relay being used for stereo pairs of speakers (I am dense..but willing to learn)? If someone could recommend some parts and maybe a schematic?

Click to expand...

There are two wires to each speaker, often labelled +ve and -ve. You only need to switch ONE of them!.

So assuming you're switching the +ve wire (it doesn't matter which).

1) Connect the +ve output from the amplifier to the common of one half of the relay.

2) Connect +ve from speaker one to NC contact.

3) Connect +ve from speaker two to NO contact.

4) Connect all three -ve wires together.

5) Repeat for other channel using second half of the relay.

With the relay not powered the +ve from the amplifier connects to the +ve of speaker one (NC - Normally Closed contact). If you energise the relay, then the +ve of the amplifier then connects to the +ve of speaker two (NO - Normally Open).

Cabinet switcher redux

ahhh...[envision lightbulb here]...most ingenious Mr. Goodwin.

Now for the other shoe. In some cases, I may not want to haul all those speakers around, however, the programmed interface is still going to say 'switch to the other cabinet/s'. I don't want to re-program for those instances. Is there a way that the unit could react to the fact that only one set of speakers is connected by either not switching (tricky, I'm guessing) or the result of switching be status quo (less tricky, I'm guessing)? Perhaps this would also work as a kind of safeguard against running without a load??

I think I also want to wire up some kind of indicator light to tell me (without leaning in and listening) which cabinets are being powered. I think I can figure that out for myself, are there any 'gotchas' in doing this?

Is this powered by a battery or does the external switch send the juice?

many thanks

BTW - there is a typo in one of the headings-"exprienced members find a solution"
The entire heading is "Are you building an electronic project or want to? Maybe you need some assistance? Come and submit your electronic questions here and let our exprienced members find a solution."

Who gets notified?

GtarPlaya11 said:

ahhh...[envision lightbulb here]...most ingenious Mr. Goodwin.

Now for the other shoe. In some cases, I may not want to haul all those speakers around, however, the programmed interface is still going to say 'switch to the other cabinet/s'. I don't want to re-program for those instances. Is there a way that the unit could react to the fact that only one set of speakers is connected by either not switching (tricky, I'm guessing) or the result of switching be status quo (less tricky, I'm guessing)? Perhaps this would also work as a kind of safeguard against running without a load??

I think I also want to wire up some kind of indicator light to tell me (without leaning in and listening) which cabinets are being powered. I think I can figure that out for myself, are there any 'gotchas' in doing this?

Click to expand...

You could place an LED (with series resistor) across the relay coil, this will light when the relay is energised - the relay coil also requires a reverse connected diode across it.

Is this powered by a battery or does the external switch send the juice?

Click to expand...

It's powered by whatever you want to power it from - personally I would have thought a foot operated mechanical switch, pressed by the guitarist would be the best solution for switching cabinets. Doing it via Midi seems a bizarre idea?.

Cabinet Switcher Redux

Nigel,
A foot-operated switcher would be simple. Not the best, though. Here's why:

1.) Speed - you need to accomplish the whole change, all the effect changes, preamp changes, and now, cabinet changes - very quickly. Midi is really swell for that purpose and I use it for everything else.

2.) Proximity - I don't want more speaker wire running than I need. Either there would be quite a bit, if the switcher were near me, or the switcher would be further than I would like resulting in a deterioration of 1, above.

I want the switcher to be in the rack with the amplifier. Ideally one set of inputs (from Senor TubeAMp) and two sets of connectors going to the cabs. An LED (thanks..I think) on the front indicating what's currently powered. What is the reverse connected diode etc? do you have a diagram for the IE Dummies of the guitar world?

When only one set of spkrs is connected the unit 'knows' that and the switcher does nothing. It seems likely to me that a physical defeat of the switcher would be possible via the fact of a connector being inserted or not?
[IE some kind of cross-connection of the output connectors which is broken by inserting the spkr connector plug]

The activation of the switcher will be via a programmable relay switch which is an existing component of the MIDI programmable preamp. The on/off condition of that relay is set via MIDI. This exists and all I need is the connection to the new 'switcher' DPDT relay to tell it to do it's thing.

Nigel Goodwin said:

Except it's NOT typical construction - Marshall amps (and all others) have used PCB's for decades. It's just a marketing ploy to charge more money for exactly the same amp - PCB, tag board, tag strip, or even direct wiring, none of them affects the sound.

From a personal point of view, as I don't make PCB's, it's the sort of technique I'd use to build a valve amp - and from a servicing point of view it's often easier to repair, PCB versions are often difficult to work on due to the short wires etc.

I fully agree, it's a fine example of 1950's layout (and looks great) - but unfortunately it's not the 1950's any more!, and it's just extra expense for no advantage.

Click to expand...

Certain models are still constructed that way and back then it was for good reason. Solder posts provide for much better mechanical connection first before the solder gets applied. These amps may see many miles on the road of banging around in and out of venues. A thick phenolic board, stout soldering posts, tube retainers, thick metal chassis, well gussetted cabinetry all make for a product that can withstand the rigors of the road, rail or by air. You've serviced enough tv sets to witness loose solder pads, etc. and that's from a device that likely remains in place over the long run.
The cheapest of tube amps have their sockets mounted to the PCB which is a big mistake!

Yes the output Xformer is a major factor in sound quality, but I believe the speaker is #1 foremost.

Think I found a way maybe

GtarPlaya11 said:

When only one set of spkrs is connected the unit 'knows' that and the switcher does nothing. It seems likely to me that a physical defeat of the switcher would be possible via the fact of a connector being inserted or not?
[IE some kind of cross-connection of the output connectors which is broken by inserting the spkr connector plug]

Click to expand...

I found this connector - Switchcraft J12A Shorting JAck - which I think I could wire up to defeat the switcher, or route the connection back to the other spkrs. Am I nuts?

GtarPlaya11 said:

I found this connector - Switchcraft J12A Shorting JAck - which I think I could wire up to defeat the switcher, or route the connection back to the other spkrs. Am I nuts?

Click to expand...

You're not nuts, but you are making this overly complicated, IMO. Why have the speakers going through the switcher if you won't be switching them? I get everything else you're saying about having everything switch simultaneously and such (I'm also a guitar player), but I don't see why you'd want the switcher to "know" if only one set of speakers is connected. If using one set of speakers, don't plug them into the switcher... simple enough, no? Just plug the one set you are using directly into the amp. The switcher will be fine with nothing connected to it, or you could disconnect it completely (the latch/unlatch connection on your MIDI controller will also be fine with nothing connected to it).

Let me make sure I'm understanding this correctly and I have exactly what you want to do down here...

You already have some sort of MIDI switching device such as a controller with a latching output (usually used so that the MIDI controller could be used to control the channel switching of an amp, basically designed to be plugged in in place of the amp's usual footswitchl). You're going to use this latching output to control this speaker switcher of yours and I assume it uses a 1/4" tip-sleeve ("phono," just like the instrument or speaker cable) connection?

What you're looking for would be something like this attachment then. You will need to provide an appropriate power source from something. A battery could be made to work, but I'd go with a DC adapter. The value of the resistor will depend on your power source and the requirements of the relay, the diode could be just about anything (as long as it has a reverse breakdown voltage greater than Vcc). You'll need a total of 7 1/4" jacks. 4 for the 2 sets of left/right outputs, 2 for the left/right inputs, and 1 more for the latch on the midi controller (preferably chassis isolated, at least for the 6 carrying the speaker signals... I can't guarantee something bad would happen if your speaker return path isn't isolated from your switching circuitry ground, but I wouldn't think it a good idea).

But I WANT to use the Plutonium power source!

Thanks JB! That was very helpful. I do tend towards the overly-complicated and you are, of course, completely correct...don't plug the switcher in. Simple.

Thanks for your post and the diagram/schematic thingie. They will help me immensely as I am a complete IE dummie.

I forgot about it while I was posting here the other day, but I just remembered that Weber sells a kit that'll do pretty much exactly what you're looking for. You'd just need to find a 6.3VAC transformer to power the thing, the appropriate jacks, a box to put it all in, and some mounting hardware.

It goes for $9.00 in kit form or $13.00 pre-assembled. One would assume that it would come with directions for hooking it up, but I've never used one so YMMV. You could always try emailing them with any questions.

That would be the quick and easy way, unless you're looking for that, "designed it myself," feeling from the thing.

Anyway, here's the address for that kit:
**broken link removed**

Cab Switcher from Weber

This Weber thing looks good. I suppose I would actually need two of them to do the switching from/to pairs of speakers wired in stereo (DDM)? Or could I get it in kit form and swap in a DPDT relay? Maybe that's a question for Weber?

Thanks again!