Stereo In/Out - Series & Parallel Switch

[facon]

I've been racking my head for a while on this. I can't figure out how to get it down to a 4PDT switch. I'm trying to make a switch that will allow me to use my delays in stereo/parallel or in series. Both the input and output are stereo. In parallel everything would remain true stereo. In series it would be summed together, sent through the two delays in series, then split back out to stereo. I would love to be able to figure out LED indicators as well. I have a design for 5DPT without LEDs, but I'm hoping that's just my lack of experience showing. Can anybody help me sort out this wiring?

While in parallel the signal flow would need to be:
Input 1> Send 1 > Return 1> Out 1
Input 2 > Send 2 > Return 2 > Out 2.

While in series the signal flow would be:
Inputs 1 and 2 summed > Send 1 > Return 1 > Send 2 > Return 2 > Outputs 1 and 2 split.

I don't mind going with a relay if necessary.

[slacker]

I've only had a quick think about it so I might be wrong but why do you need 5 switches.  You only need to switch return 1, out 1 and input 2.
Return 1 goes to out 1 or send 2. Out 1 goes to return 1 or return 2. Input 2 goes to send 1 or send 2.
You might need to add some mixer resistors to combine the inputs.

[facon]

I have to be honest, this kind of stuff with switches makes my head explode. I'm not very good at it.

What about input 1 and output 2? Input 1 needs to be summed together with 2. I'll be using stereo chorus, flanger and phaser effects that send out seperated stereo signals. If they aren't summed together, but are disconnected, then you won't hear the effect. Same with the output, it will be connecting to two separate amps, so it has to be split when in series to send to both.

[slacker]

Input 1 always goes to send 1, out 2 always goes to return 2 so they don't need switching. In series mode you can just connect out1 to out2.
Run in1 through a resistor to send 1. Run in2 through a resistor then switch that either to send 1 or 2. The resistors will mix the signals in series mode. Use something between say 1k and 10k and they won't have any effect in parallel mode.

[facon]

I think I'm following so far. I don't understand why it would be better to send the signal through 2 resistors. When in parallel, wouldn't this just lower the overall volume?

Also, you originally said that Output 1 switch needs to select between Return 1 or Return 2. Wouldn't it make sense that it only needs to go to Return 2 and keep the other without a connection? This way it will connect one and 2 together during series, but keep them separate during parallel since Return 2 is hardwired directly to Output 2.

[nocentelli]

I'd have sworn there was a wiring diagram using a 3pdt posted in this thread a few hours ago: When i saw it this morning, it looked like it should work ok (irrespective of mixing resistors).

[facon]

It seems like the one I posted should work, but I'm still not sure about the resistors. I'll wire it up and keep that connection open so I can experiment with alligator clips.

[slacker]

Looks like that should work, yes you're right you don't need that extra connection on out 1, I didn't draw it out otherwise I would probably have seen that, I just counted all the things that needed switching and saw that the most you needed was 3 DPDT.

You need the resistors in series mode because you can't reliably mix two outputs just by connecting them together, it might work in some cases and not in others. In parallel mode there is a voltage drop but it will be too small to worry about, say your delay pedal has a 1M Ohm input impedance and you use a 10k resistor, that will make the voltage 99% (1000k/1010k) of what it would be without the resistor, you can't hear that.

[facon]

Thank you very much for your help!

[nocentelli]

Presumably one could have a mono input to a buffer feeding a split signal to the two input wires: I'm guessing the resistors would still be a wise idea?