Two effects in parallel

[gtg975n]

I was curious if anyone has experience with running two (or more) effects in parallel.  My understanding is that you need a way to control the mix for the two pedals (the Boss LS-2 is the only pedal I'm aware of that can do this BTW).  I'd like to build a a boost  (for sheer power) and an overdrive (for breakup) all in the same enclosure with a knob to mix the two.   

[B_of_H]

I've never built this project but here ya go:

http://www.runoffgroove.com/splitter-blend.html

[maysink]

The Toneman ParaMix over at guitarpcb.com is a very useful tool. It mixes your input signal (effect A in your scenario) with one or more effects in series (effect B to you) and can deal with phase issues.

[eniacmike]

does anybody know how this was done in the way huge CAMEL TOE. It was a dual pedal with a green rhino (ts9) and a red llama (tube sound fuzz) in the same enclosure. There is a switch that selects series or parallel, no controls for balance as far as I know.

http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=1 1869&g2_serialNumber=3

[stecykmi]

I doubt it's too complicated. series is simple enough, just one output feeds into the next input. parallel just has the input and output nodes connected, respectively.

that's can be done with a dpdt switch if i'm not mistaken.

[eniacmike]

this is what I came up with for a series/parallel switch. The biggest problem I see is that I cannot ground the input to either effect in bypass while the switch is in series mode because it would mute the input of the other effect to ground. I generally like to mute the input wire to ground in bypass to prevent buildup in the caps which would cause a pop. I can't really figure out a way around that.

the other potential problem I see is that when the pedal is in series mode the extra wire going to input A and the other extra wire going to the output jack will just be hanging loose which is a potential problem for noise.

also if there was a way to simplify it to use a dpdt that would be great. I had to use a 4pdt to figure it out. if anybody can verify or help me out I would appreciate it. I am probably going to build my "camel toe" in the next week and I will try it out.

-mike

[rhcp311]

this is what I came up with for a series/parallel switch. The biggest problem I see is that I cannot ground the input to either effect in bypass while the switch is in series mode because it would mute the input of the other effect to ground. I generally like to mute the input wire to ground in bypass to prevent buildup in the caps which would cause a pop. I can't really figure out a way around that.

the other potential problem I see is that when the pedal is in series mode the extra wire going to input A and the other extra wire going to the output jack will just be hanging loose which is a potential problem for noise.

also if there was a way to simplify it to use a dpdt that would be great. I had to use a 4pdt to figure it out. if anybody can verify or help me out I would appreciate it. I am probably going to build my "camel toe" in the next week and I will try it out.

-mike

I'm curious about this exact same issue. Did anyone ever test Mike's diagram to see if it worked well?

[oldhousescott]

You can't just tie the outputs together, as each output will look like a dead short to the other. You need some resistance on each output to mix them together. It can be as low as 1k, but 10k on each is probably better, that way each output sees 20k to ground, which it should have no problem driving. Because of the voltage divider created, each output will only contribute half of its signal voltage to the mixed output, assuming fixed resistors. If using a pot, like the splitter-blend, you can get full output from one or the other output, or any blend in between.

[rhcp311]

You can't just tie the outputs together, as each output will look like a dead short to the other. You need some resistance on each output to mix them together. It can be as low as 1k, but 10k on each is probably better, that way each output sees 20k to ground, which it should have no problem driving. Because of the voltage divider created, each output will only contribute half of its signal voltage to the mixed output, assuming fixed resistors. If using a pot, like the splitter-blend, you can get full output from one or the other output, or any blend in between.

Just to get a bit of clarification, which outputs are you talking about? He has a lot of things labeled as "output" in that picture like the return from circuit a, return from circuit b, the output from the first footswitch, the output from the second footswitch that goes to the output jack, etc. Thanks for the help, I just want to make sure I know exactly which one you're talking about.

[oldhousescott]

In the splitter blend circuit, notice the 25k pot strapped across the outputs of U2A and U2B. Those are the outputs to which I'm referring. You could replace the pot with two 10k resistors in series, one end of each tied to the electro caps on each output, and the junction being the mixed output. HTH.

[rhcp311]

In the splitter blend circuit, notice the 25k pot strapped across the outputs of U2A and U2B. Those are the outputs to which I'm referring. You could replace the pot with two 10k resistors in series, one end of each tied to the electro caps on each output, and the junction being the mixed output. HTH.

So, in the picture with the 4pdt switch, where the orange jumper is in the top right, if I just added a 10k resistor to ground from each one of those lugs, would that probably solve the problem? I'm curious if that would work, or if I'm misunderstanding you somehow.

[oldhousescott]

In the passive circuit with the 4PDT, you would put the resistors in series with the yellow wires coming from the Out A and Out B terminals.

[rhcp311]

In the passive circuit with the 4PDT, you would put the resistors in series with the yellow wires coming from the Out A and Out B terminals.

Interesting. Would that make any sort of difference when the switch was set to be in series though?

[oldhousescott]

Not greatly. The input impedance of an average pedal is, let's say for argument, 250k (that's probably on the low side). The 10k resistor on the output will form a voltage divider with the 250k causing a voltage drop to the input of the 2nd pedal of about 4%, nothing to really worry about.