Help with A/B/A+B Loop Box

[amonte]

I want to convert my old DOD 250 into a loop box.  I want to be able to switch between A or B loops, or have A stacked on top of B.

I understand the switching necessary for the A or B - that's pretty straightforward.  What I'm having a hard time wrapping my head around is incorporating a second switch to go from A or B to A + B.  I haven't been able to find any schematics for this.  I've only got DPDT and SPDT switches handy, so for now it's going to have to be completely passive with no LEDs. 

Any assistance is greatly appreciated.

Thanks!

[kodiakklub]

its called an ABY box. you need 2 DPDT switches to do i passively. there is a schem floating around the web somewhere for the morely version. also im pretty sure there is one on GGG

[amonte]

I wasn't sure if it was still called an ABY pedal if it used loops.  I thought that was more one input/three outputs.  I'm looking for a pedal with one input, one output and two loops which can be toggled between or stacked together.  I haven't seen a schematic like that anywhere.

[iq01221]

2 x 3pdt and a little of imagination...

[DiscoVlad]

A Boss LS-2 is what you want.

[amonte]

Thanks for the replies.

The LS-2 isn't really what I'm looking for as you can't toggle from A+B or A/B loops.

As for 3PDTs, is there any way to do this with DPDT switches if I forgo the LED?

I guess if I have to, I will settle for one switch toggle of A or B, or simply two isolated loops. 

[iq01221]

...As for 3PDTs, is there any way to do this with DPDT switches if I forgo the LED?

I guess if I have to, I will settle for one switch toggle of A or B, or simply two isolated loops. 

A/B surely, I've already done that.. once.. dunno, maybe twice.
But A+B...I don't know if it's possible put leds.
Actually, I need to do one of these...

[trixdropd]

Not sure how to make what you want but this http://championpedals.com/tgc2.htm will do what you need with an external 2 button footswitch.

[kodiakklub]

oh sorry i missed a few key words in your OP. oddly enough my first ever build was for what you want PLUS a tuner mute. it was a disaster. it was a 1590D with 11 1/4" jacks, 5 LED's and 5 3PDT footswitches. it was a tuner mute/ABY/with 2 effect loops. it worked, but i destroyed the signal and murdered all the mids and highs. then i put an orman IC buffer in it to try and get the signal back, but would have needed the equivalent of probably 4 IC buffers in series or something. i dont think i ever got farther than hand drawing the signal routing. i know i ended up taking the morely ABY circuit plus a tuner mute circuit, plus one true bypass loop off each A and B. needless to say, it turned into a parts box.

[DiscoVlad]

Like the other replies say, it's not an easy thing to do completely passively especially with LEDs, however using some relays (or 4066/optocouplers/fets for solid state switching) to route your signal, and some logic (e.g. a small micro controller) should let you turn each loop on in whatever combinations you desire.

That's why I suggested the LS-2, as it seems to do most of what you want with one footswitch, so would be a good place to start.

As usual RG has an excellent writeup on exactly this topic: http://www.geofex.com/article_folders/fxswitchr/fxswitchr.htm

[amonte]

Like the other replies say, it's not an easy thing to do completely passively especially with LEDs, however using some relays (or 4066/optocouplers/fets for solid state switching) to route your signal, and some logic (e.g. a small micro controller) should let you turn each loop on in whatever combinations you desire.

That's why I suggested the LS-2, as it seems to do most of what you want with one footswitch, so would be a good place to start.

As usual RG has an excellent writeup on exactly this topic: http://www.geofex.com/article_folders/fxswitchr/fxswitchr.htm

Actually, I'm fine leaving the LEDs out If that makes doing it passively possible. 

I will check out RG's article - thanks.

[harmonic]

I built something similar. Each loop is either on or bypassed; to switch between both, just stand on both switches at the same time! ;-)

http://mcvey.org/cam/projects/pedals/loopy-deux/

[slacker]

or have A stacked on top of B.

What do you mean by this? Do you want A and B both on in parallel or in series A into B?

[kodiakklub]

oh oh oh series vs parallel!  slacker can you please show a mega simple diagram of series vs parallel wiring? as in just 2 pickups and a switch? i never fully understood it and im a very visual guy.

[slacker]

Parallel is like this, so the two loops are next to each other, with the input going to both of them and the outputs of A and B mixed together. If A and B were pickups "In" would be ground and "Out" would switch between A or B or connect to both, from there you would go to the volume pot or tone controls.

          ____A___
In____/               \____Out
         \____B___/

Series is like this, so the signal goes through A and then through B. I'm guessing this is what amonte means by "stacking". Again if they were pickups "In" would be ground and "Out" would go to the volume pot. To switch you could bypass A or B, like two pedals in a chain.

In____A__B___Out

Hope that makes sense.

[iq01221]

For series looping, a 3pdt can do the work. But for paralel, U can try this: http://www.runoffgroove.com/splitter-blend.html. Seems to be simple...
Best regards!

[amonte]

Hey guys, thanks for all the replies.

What I was thinking of was two loops, in series.  Switch 1 toggles between A and B and switch 2 runs A into series with B.

I suppose the most painless way to do this is simply two loops, in series, and just stomp on both to turn both on at once. 

[amonte]

It could be the heat talking, but I think I might have figured out a way to do this!  Found some DPDT toggle switches and a bunch of jacks so I'm going to try a prototype.  If it does indeed work, I'll share it with you guys.

The one thing that maybe isn't clear and my post (and might be what's making it seem hard) is that there is no real bypass mode - like an AB switch, what I am looking to do is A by itself, B by itself or A into B.  There's never a setting where everything is off. 

[Seljer]

The tricky part is going from A+B back to either A or either B

Your options are:

• three momentary switches, and a whole ton of relays to make up the logic to work the circuit, my napking sketch has like 6 of DPDT relays and thats not including the actual audio switching
• three momentary switches, two latching relays and a some regular diodes
• momentary switches, a dual flipflop IC and some other parts, then two regular relays
• momentary switches, a 70cent 8 pin microcontroller to handle all the logic and two regular relays

I can't think of any way to this with pure mechanical switches.

I suppose the most painless way to do this is simply two loops, in series, and just stomp on both to turn both on at once. 

Well, you only have to stomp on the loop thats currently deactivated. You're right about that most painless way of doing this

[GGBB]

Crude, but gives you A, B, series and parallel options with just two spdt switches:

    ----A----
    |     y0/\y1
in---      /  ----out
   x1\/x0 /     |
      ------B----


x0+y0 = A->B
x0+y1 = A
x1+y0 = B
x1+y1 = A||B