4 way ABY switch

[mmaatt25]

Hi,

The guitarist in a band I'm in has asked me if I can make him a 4 way ABY switch.  I've made passive ABY's no problem, but four?

What he wants to do is have four guitars plugged into one amp and kick a switch for each guitar.  He's currently using two ABY boxes daisy chained, so he's only actually got three guitars on the go.

Has anyone got passive schematic?

Could I use this http://www.muzique.com/schem/mixer.gif with DPDT stomp switches to ground (+LED so he knows which channels active)??

Any thoughts welcome.

Many thanks

Matt

[Seljer]

Latching relays and four momentary switches with some diodes to route the switching logic. Latching relays only need current when changing state and have two coils, one to connect the switch and one to disconnect. You route each switch to turn on one of the relays and turn off all the others.

You'll need power for it to work but the signal will be connected only via mechanical contacts.

[mmaatt25]

Hi,

This sounds like exactly what he wants.  I spoke to to him about it again to clarify what he wanted. He wants to kick a switch two (for example) and the  guitar on that line is "live", what he didn't want to do was do dance and turn one off and then the other on.
I think having to kick to switches is pretty simple and would also mean I could build it very simply using Jack Ormans mixer.
It sounds like what you've described is more in line with what he wants. Have you any schematics, I've built various pedals but never done anything with relays etc.

Many thanks

Matt

[R.G.]

In my experience, latching relays are great for saving power, but add significantly to the complexity of the circuit needed. If you have to have power to it, and it's a DC power adapter, not a 9V battery, nonlatching relays are easier to use.

It is easy to implement a "radio button" switching setup with CMOS logic. There is a schematic for an easy one at geofex in the article "A Programmable FX Switching System http://geofex.com/Article_Folders/fxswitchr/fxswitchr.htm, in illustrations 7 and 8. The 74C373 happens to do this in a straightforward way for any number up to eight.

You're probably going to want to read the other articles on relays for audio switching and footswitching systems at Geo as well.

[mmaatt25]

Thanks RG,

I've read your articles on relay switching at geofex. This is the direction I want to go in and now I need to actually get some 5v relays.

With relays they seem to be rated with regard to their operating voltage 5v, 9v & 12v etc. What I'm not sure about is the value (voltage/current) rating for the signal from guitars/effects (the signal path) that the relay is actually switching. Relays like all switches are rated for load.

Thanks

Matt

[PRR]

> rating for the signal from guitars/effects

If you have a 230V 10A motor you need a pretty big relay.

Guitar/effect level is under 1 Volts and 0.000,1 Amps (0.1mA) maximum. Typically less if you switch between LOUD passages. "teeny".

The smallest mass-market relays may be 25V 50mA. That's dozens of times sturdier than you need.

So "any relay"(*) will switch audio. Select for convenient coil voltage and price. TIP: shop small-audio suppliers such as pedal and gitar-amp sites to avoid being overwhelmed by too many choices.

(*) There "is" such a thing as too little load. The big 10A contacts on a motor relay expect large energy to keep the contacts clean. Telephone companies who had literally room-fulls of relays went to precious metals sealed in glass for ultra-reliable small-audio switching. Mostly the small (not huge) modern relays do all right for stage-gear work.