Using 1/4" switching jacks

[Gumby212]

Im lookng for some help using swifching jacks to somehow give a stereo pedal mono capabilities. Im building a stereo overdrive pedal that has 2 seperate overdrive circuits in it, one going to the left input and output, the other going to the right input and output. Ide like to either add a stero/mono toggle that sums the left and right together so both circuits can be heard together on the left input and output only, or use switching jacks to somehow make it to where when the right side us not plugged in, the left automatically sees both circuits. Is this possible, and if so, how exactly do i wire it? Ive never used switching jacks so im not sure how exactly they work. Any help would be much apprecuated. Thanks!

[samhay]

The schematic for my stereo reverb is here:
https://samdump.wordpress.com/welcome/projects/stereo_reverb/

I used switching jacks on the input and output to switch the input and/or output to mono depending on what is plugged in.
A few considerations:
You will need some resistance on the output so you can passively sum these to mono. If the 2 signals are not in phase you will get cancellation, which is probably undesirable.
If the 2 effects have vastly different input impedance, you may get some weirdness due to loading of the higher impedance circuit if you sum the inputs with only 1 input connected.

[Gumby212]

Are the resistors that help the summing the 1ks at each input and output? Are the switching jacks only necessary on the left (mono) input and output? Thanks for your help!

[GGBB]

Yes - in that circuit the 1ks are the summing resistors.

The switching jack is typically the "optional" jack - the one that isn't used for mono. Its switch is normally closed and connects the optional/second/stereo in/out to the primary/mono in/out. The switch is opened, breaking the connection, when the plug is inserted.

[Gumby212]

Awesome. So let me describe the pedal im building a little better and hopefully you can help me figure out the issue im having. Im building a stereo overdrive pedal for a buddy, with 2 seperate overdrive circuits attatched to one footswitch. The guy runs a 2 amp rig and wanted to activate 2 overdrives at once without using a looper pedal. He also wanted bypass switches for each circuit, so it can be more versatile in which circuit he has active. He needed 2 inputs as well as 2 outs bc this pedal is going after his ABY pedal in his chain. I have this pedal working on a breadboard, using a lovepedal amp 11 for side A and a BSIAB for side B. They are run off of one 4pdt footswitch, used like 2 millennium bypass switches side by side to give me true bypass with an LED for each circuit. I used 3pdt bypass toggles for each circuit so i had the capability to kill the LED when the circuit was bypassed. Ive even added clean blends for each circuit. So far so good, until i started investigating ways to give this pedal mono capabilities, where both circuits could be active via the left input and output only. At first i thought a toggle would do it, but then was told  that switching jacks would be the way to go. I thought i understood how it should work but am failing getting it to work on my breadboard. I put the switching jacks on the B (right) input and output, put the neg to ground, ran the pos to their correct spots on the breadboard, and wired each switch to an open spot on my board. I was then able to run wires from the pos of input A and output A to the switch, thereby combining the 2 inputs and outputs together when the right side gets unplugged, via the switch making the connections. In stereo mode, this pedal works beautifully. I understand a resistor, or a few in series?, should be involved on the output, so between the switch that connects pos A to pos B on the outputs, i put a 2.2k resistor. This all seemed to work, but the A circuit did seem to be quiter than the B circuit, but I do get both circuits down the left side only. The really confusing thing is the weird shit that happens when i try and use my bypass toggles. I guess im confused as to where i should take the input and output from circuit A to the switches for circuit B's input and output. Theres multiple spots in the circuit i could do this, and i seem to have problems in every wiring configuration i try. Im also a bit confused on where to put my resistor. Is between the pos of output A and the switch on output B the only place fir a resistor? Im using a 2.2k bc of a stereo to mono toggle schematic i found online, but it also gave me trouble. I have a feeling its the wiring for the bypass toggles causing the confusion in my brain. Anyway, your schematic really helped put this idea into perspective, but after @#$%ing with it all night with no luck, im still pretty confused as to how this should be wired. I hope my pedal discription was clear and made since. Its an oddball pedal for sure, but will be an awesome build for someone with a stereo setup. Anymore wisdom on the subject would be much appreciated. Thanks again! 

[samhay]

This won't work in mono with the bypass switching you are using.
In mono, you are running the two effects in parallel (is this really something you will find useful?). If you then bypass one of these effects, you also effectively bypass the other because the input gets connected via any mixing resistors to the output.

If you only need to make the input mono so the signal is split to 2 outputs, you can make this work with a switching jack(s) on the input.

[Gumby212]

Hmmm, you definitely explained the issue im having. The bypass toggles @#$% everything up. What about a toggle that swaps the inputs and outputs, therby giving either effect on either input/output? Would using a 3 way toggle and making the center position see a blend of both circuits be possible? Left position seeing the left circuit, right position seeing the right circuit, and the middle seeing both... is this possible? Im not sure what this toggle would do when using both sides of the pedal in stereo. Would making the switch active via switching jacks be possible? Where once the right sides are unplugged, the switch is active, therefor only working when using in mono?... Its a specialty build for a buddy with a stereo rig who wanted to turn on two overdrive circuits (one to each amp) at once without adding a looper pedal to his board. So thats where the pedal idea came from. Im just trying to make it more versatile by allowing access to both circuits via the left input and output only. Any ideas or wiring tips would be greatly appreciated. Thanks!

[samhay]

Sounds like you have mission creep. More versatile isn't always desirable.



Yes, you can have a switch that will only do something when a switching jack is not in use.
However, this has some restrictions as one of the switch contacts will be connected to the plug once it in use. If your switch is going to ground or e.g. the circuit input then this is not a problem.

[Gumby212]

I could put the input on a switching jack for mono use, but i would love to get both circuits on the left output only, for use of a single amp setup. Im not sure whats easier, a switching jack for the input snd s toggld for the output, or both on a toggle. As you brought to my attention, i guess using switching jacks for both wont work bc of the bypass switch wiring. The blend of the two circuits isnt that important, and from all the testing ive done is not very possible to get to sound great.ivegotten both circuits summed to the left side, but it didnt sound geat. At one point i accidentally bypassed the footswitch with one of the circuits, where it was active even when the pedal was bypassed. Once i activated the pedal, and got the 2nd circuit, i actually had a nice blend of both circuits, but one was bypassing the pedal entirely so of course i didnt want that. With that configuration tho, both circuits did blend beautifully in parallel together, leaving me to believe that it is possible to do correctly without one circuit bypassing the pedal completely... However, getting both circuits on a toggle so you have the option for either circuit on the left side of the pedal has to be an easy, dpdt toggle wiring job, right? Like, a toggle that swaps the inputs snd outputs (or just the output with a switching jack on the input?) Any isnight as to how i would wire a toggle for this application? I do not have a schematic drawn up but could give u a block diagram of the signal path of the pedal if that would help with an answer. I appreciate your time and interest in my issue. Any helpful tips would be much appreciated, as im only about 6 months into this hobby, and messing with basic electronics in general, so i still have lots to learn. I realize its an oddball pedal and its been hard to get help on it. Thanks again!

[samhay]

>However, getting both circuits on a toggle so you have the option for either circuit on the left side of the pedal has to be an easy, dpdt toggle wiring job, right?

Sure, but you only need a SPDT to switch either output to e.g. left out

I think you need to draw the block diagram. This way you can draw in as many switches as you like.
If you use the _\_ notation (for SPST or equivalent for XPYT) then you can trace out the signal flow for each through each switch. If you end up going around in circles, you have a problem.

[Gumby212]

This was the best diagram i could put together. Sorry for the ameture drawing but hopefully you get the idea if the signal flow through the pedal. I labeled the A side with letters and the B side with numbers. Hopefully it makes since and isnt too confusing.

[Gumby212]

Well that didnt work. Not sure why it wont post my picture. Of course it has to be difficult..

[samhay]

Upload to something like imgur or google drive then share the link

[Gumby212]

https://drive.google.com/open?id=0B7eftyRLt-eJS3d0T2hjZ25IdVU

Hope that helps you understand the signal flow of this pedal and what im trying to do.
I labeled the A side with letters and the B side with numbers. Thanks again for taking a look!