Building an A/B + C Loop Switcher

[laundryman]

Hi,

I've made several PCB's over the last several months and want to build a loop switcher, but I'm still very new to how everything works.

I'd like to make this: https://www.americanloopers.com/collections/a-b-boxes-a-b-c-a-b-y/products/ab-loop-selector-with-added-c-loop-select-loop-a-or-b-then-add-loop-c-with-premium-switches

It's a loop switcher that allows you to select loop A or B, then C is a third loop on toggle that can be added (such as A or B being Lead or Rhythm, and C being delay and reverb).

I've found a few schematics and guides for just an A/B loop switcher, but I'm not sure how to add the toggled C loop.

Ideally I'm hoping to be able to expand it to a 3-way switcher plus toggleable 4th (A/B/C + D).

Any help would be great - thanks!

[iainpunk]

I've found a few schematics and guides for just an A/B loop switcher, but I'm not sure how to add the toggled C loop.

the +C loop is just like a normal pedal bypass in series with the A/B switcher, a bit like this

the in jack is replaced with the wire coming off of the A/B switcher.

Ideally I'm hoping to be able to expand it to a 3-way switcher plus toggleable 4th (A/B/C + D).

that would require a 3way switch of some sorts (hard to find / really expensive), or a fancy 'relay + logic' board

a little tip to avoid ground loops, which cause hum and hiss; use plastic jacks and only ground the ''send'' jacks, not the return jacks, since the grounding for that side runs through the pedals already, you don't want to create a circle/loop of ground path

cheers

[BJM]

Ideally I'm hoping to be able to expand it to a 3-way switcher plus toggleable 4th (A/B/C + D).

that would require a 3way switch of some sorts (hard to find / really expensive), or a fancy 'relay + logic' board

I think for for A or B or C you can also use two footswitches. American Loopers sells them also,
https://www.americanloopers.com/collections/a-b-boxes-a-b-c-a-b-y/products/abc-loop-selector-select-loop-a-or-b-or-c-with-master-bypass.

The third switch in this looper could then by used as bypass for "D". You don't need a PCB, these loopers are all passive and only need power for the LED's.

You could also try a three way splitter/mixer and mute the unused loops by switching them to ground.  I'm building something like that at the moment, with three rotary switches and one 3PDT footswitch. Bit difficult to explain but with the rotary switches I can choose which loop is on or off  before I stomp the footswitch, bit like two different presets. I can go from A>B or B>C and also with parallel combinations (A to B+C f.e.).
No logic board, but it's limited. I can only choose between only two combinations of three loops (4 loops if I buy an expensive 4PDT footswitch), but that's enough for me (logic board is also too difficult for me..... but I'm sure Iain can help you out here if you want to try that).

[iainpunk]

Ideally I'm hoping to be able to expand it to a 3-way switcher plus toggleable 4th (A/B/C + D).

that would require a 3way switch of some sorts (hard to find / really expensive), or a fancy 'relay + logic' board

I think for for A or B or C you can also use two footswitches. American Loopers sells them also,
https://www.americanloopers.com/collections/a-b-boxes-a-b-c-a-b-y/products/abc-loop-selector-select-loop-a-or-b-or-c-with-master-bypass.

The third switch in this looper could then by used as bypass for "D". You don't need a PCB, these loopers are all passive and only need power for the LED's.

You could also try a three way splitter/mixer and mute the unused loops by switching them to ground.  I'm building something like that at the moment, with three rotary switches and one 3PDT footswitch. Bit difficult to explain but with the rotary switches I can choose which loop is on or off  before I stomp the footswitch, bit like two different presets. I can go from A>B or B>C and also with parallel combinations (A to B+C f.e.).
No logic board, but it's limited. I can only choose between only two combinations of three loops (4 loops if I buy an expensive 4PDT footswitch), but that's enough for me (logic board is also too difficult for me..... but I'm sure Iain can help you out here if you want to try that).

the biggest down side of using 2 switches for 3 channes is that its not A/B/C but instead its (A/B)/C. so one switch chooses A or B and the other switch chooses between C and the first switch.
if its on C, the A/B switch does nothing until you switch the 2nd switch back.

doing a 3 option logic board can be done with a single switch, using a ring counter circuit. if you want 3 options with 3 switches, you can do it with 3 SR flipflops.
both options use momentary switches, and you can chose between relay or Jfet switching.

cheers