Is This Type Of Amp Switcher Possible?

[pompeii0]

I don't know if this is possible, but here is what I would like to do. I have a Bradshaw RSB-18 and I want to be able to use the n/o n/c contacts to be able to switch the outputs of an a/b box to switch between 2 amps. I haven't been able to find the schematic for an a/b box that would do this. Any help would be greatly appreciated!

[petemoore]

You're talking about doing an amp switch [same input source and speaker outs?] like a DPDT bypass arrangement?
 ...what is: n/o and n/c?
 Switching output sections of tube amps like this is not something I'd recommend, a load should be present at all times when the amp is 'putting out' so as not to damage the output section.
 I would think that even the transient 'no load' condition that [I think] would be present during the act of switching could be enough to possibly wreak havoc...I could be wrong...I think I asked about this before, and got a similar answer, and that reason is why we don't see this type setup used.
 OTOH maybe I'm just not on track with the question.

[smoguzbenjamin]

A couple more details on what you're trying to achieve (a pic maybe?) would be extremely useful What are trying to do, switch between preamps or something?

[pompeii0]

Ok, sorry, I guess that I haven't be as clear as I could be. I'll try again! I want to take the output of my RSB-18 and run that into an a/b switch, and take the outputs of the switch and go to my 2 different combo amps. The trick is that I want to be able to switch between a and b by using the control output of the RSB-18 which can be set up as a normally closed or open contact. I hope that this will make it a bit clearer.

[smoguzbenjamin]

Ah. So your RSB-18 (wazzat?) has a switch that is either open or closed. Well, you'd make a normal A/B box, with isolated transformers and everything etcetc but instead of a DPDT footswitch, use a relay which you activate/deactivate with that RSB-18's switch.... Makes sense, no?

[Peter Snowberg]

Welcome to the forum pompeii0.

What you want to do is very easy to accomplish. You will need a DPDT relay and a transformer or wall-wart power supply that provides the same voltage as the relay coil wants.

Wire the adapter to the relay coil, the relay coil to the device with the switch, and then finally return the other side of the switch to the other side of the power supply. On the relay contacts there are two sets with a DPDT. One set will be used to select the amp and the other will be used to silence the amp that is not in use. Each set of contacts has a "common" (COM), a "normally open" (NO), and a "normally closed" (NC) contact. Wire one of the commons to your device output that you want to switch, and wire the other common to ground. Now wire the NC side of the first set of contacts to the NO side of the second set. Also do the vice versa of wiring the NO contacts of the first group to the NC contact on the second set. One of those contact jumper wires is also the output for amp A and the second jumper is the second amp output.

I would use a very small relay for this. The relays that are made for Telecom use are perfect. The small coils and small physical size make for less "click noise" on lines. One source of these relays is old modems. Very few people want a 1200 or 2400 baud modem today, but these modems often have nice little relays in them.

You can add an indicator LED by wiring a resistor and LED in series and placing them across the relay coil.

Take care,
-Peter

[Arno van der Heijden]

Something like this?:

http://www.tubefreak.com/crelay.htm

[Peter Snowberg]

That's perfect!

Hehehe and there's even a link back to an old version of here.

Any general purpose PNP that can handle your relay current should work fine there.

Take care,
-Peter

[pompeii0]

Could the custom A/B switch be reworked to be used as an effect loop?