Switch - OFF, ON A, ON B, ON A&B

[AndreasOlausson]

Hi,

I have an amp that I'd like to build in 2 boosters in series.

amp input jack -> [SWITCH] -> Boost 1 -> Boost 2 -> amp preamp ->...
That means basically just the guitar and two stompboxes and then the amp.

Is there a switch that can do this scenario:

OFF/OFF      - true bypass (guitar -> amp)
ON/OFF       - boost 1/true bypass Boost 2 (guitar -> boost 1 -> amp)
OFF/ON       - true bypass Boost 1/Boost 2 (guitar -> boost 2 -> amp)
ON/ON        - Boost 1/Boost 2 (guitar -> boost 1 -> boost 2 -> amp)

Is there a switch that can do this and if it is, how do I wire this?

A simple solution is naturally 2 DPDT/3PDT switches, one for each boost, but I think it would look nicer with just on 4-way toogle switch.

Thanks in advance
Kind regards
Andreas

[potul]

hi

I think the best option would be to use a rotary swtich with 4 positions. Probably a 3P4T can do the trick.


Mat

[digi2t]

hi

I think the best option would be to use a rotary swtich with 4 positions. Probably a 3P4T can do the trick.


Mat

What he said. You've got 4 possible selections there, which would need two toggle switches to configure. Use a single rotary, and you could just wire it in the order you want.

[AndreasOlausson]

Thanks!

Yeah, rotary could be an option. I'll give it a try!

Thanks again 

[PRR]

Two standard bypass/effect switches, one for each booster. Use off-off, on-off, off-on, or on-on as desired.

For a single button solution you want a ratcheting switch or the same in logic-gates. Two stomp switches or one rotary is probably the wiser path.

[R.G.]

There are 10 kinds of people - people who understand binary numbers and people who don't.   

A simple switch contact is binary: it connects or it does not.  Simple switches may be combined to make more complicated switches by linking the simple off-on together, as Paul notes, either mechanically or electronically.

An SPST switch is a simple switch. An SPDT is two simple switches, linked so one is on when the other is off. A DPDT is four simple switches, mechanically linked so that two are on and two are off at the same time, in synchronism. As a casual note, most "true bypass" uses of the DPDT use the DPDT as two simple switches in SPDT and one "bridging" switch, wasting the other simple switch. It is that reasoning that is the basis of the Millenium Bypass, the spare simple switch of the DPDT being used to turn on a light.

You can always figure out the minimum number of simple switches you will need to "count" the output states by counting up the conditions. You want:
00 (Off)
01 (On A)
10 (On B)
11 (Both A and B on)
so this will take at least four simple switches just to select the number of states. It may take more than that in terms of simple switches to actually make it work, and especially to make it easy to use.

A really useful setup that works well for humans is to have a round-robin cycling switch. Start with off; press a single pushbutton once, A turns on; press the button again, B turns on and A goes off; press again, both A and B go on; press again and both A and B turn off.

[MrStab]

i'm gonna +1 what (i think) the pros have alluded to and suggest CMOS counters or rotary switches, but i'm also gonna put it out there that using CMOS switches could widen the number of suitable physical switch types by needing less poles (as you only need to switch control voltages). plus it would help avoid problems caused by trailing the signal all the way to an offboard switch and back a few times.

i can't help but feel it would be more intuitive to just have an on/off button for each boost, though.

probably convoluted, but i'm pretty sure RG once mentioned using LM3914 ICs to make a kinda analog rotary encoder of sorts - maybe you could use a pot with detents and do that. it's a shame triple-gang pots aren't widespread, as you could actually probably control the gain of both boosts as the "encoder" pot passed through that region (compensating each boost's resistor values to complement the initial resistance, ofc). you could control one of the boost's gain that way with a dual-gang.

[PRR]

> a round-robin cycling switch.

A ratchet switch.

For a different problem, I scored a 1945-era ratchet relay. Current similar version. The long copper springs with buttons at this end are switches. You can see the cams and ratchet. The big lump pulls-down the ratchet finger.


There "are" ratchet switches. The nearest one may be a ceiling fan switch. Before cheap RF clickers, these often had a string you tugged to get off-slow-med-fast... four states. The internal switching of a fan does not directly map to your boost-boost situation, and tug is different from stomp, and these things were fairly fragile "protected" by fairly weak link-chain. Search "home depot 279094". This one clearly does not have enough wires for your job. Audio switching can be more complicated than lamp or fan switching.

Have to agree with Grant and all. Two plain pedal switches is the simplest obvious affordable solution. You don't have to invent whole new wiring diagram, you don't wonder how to add LED indicators, you don't hunt for funny switches which will also stand-up to foot abuse.

[potul]

I was assuming the OP doesn't need a switch to stomp on, but rather a manual switch. That's why a rotary seems to be the simplest approach... 

If stomp action is needed, I would go CMOS for sure.

[greaser_au]

The OP has specified 'true bypass'.... 

Two relays (the true bypass), using a 4017 and a small handful of (four for the logic, plus two for back-emf suppression) diodes  and a couple of transistors... also a capacitor and a momentary SPST switch...

david