How do I wire up dual output jacks on a pedal?

goodoldpeachphan · January 22, 2009, 03:50:24 PM

I'm putting together an analog multi-effects unit... one feature that I want to add to the unit is to have a single input jack, but dual output jacks to feed two amps the exact same effected signal (from all the effects in the chain)... So it does not have to be stereo, but rather just dual mono (I *think* is what that would be called)... Basically like the "Y" part of an a/b/y box, that is simply wired up to the output of the last effect in the chain. Also, I need the ability to just

I've done quite a bit of searching in a variety of places, but haven't found an answer to my question. Can someone help me out with a simple wiring layout diagram to answer my question?

theehman · January 22, 2009, 03:57:22 PM

Just connect the output jacks in parallel. output to both hots, grounds to ground.

goodoldpeachphan · January 22, 2009, 04:50:03 PM

Great! Thank you very much for the help. So it is just that easy? What about the cable capacitance issue... the capacitance of the cables going to the amp are summed in this case, right?

theehman · January 22, 2009, 05:22:36 PM

I don't think it would be an issue.

MikeH · January 22, 2009, 05:41:21 PM

And if it is, a simple JFET buffer can fix that.

frank_p · January 22, 2009, 07:21:11 PM

Quote from: MikeH on January 22, 2009, 05:41:21 PM
And if it is, a simple JFET buffer can fix that.

AMZ JFET Splitter:
http://www.muzique.com/lab/splitter.htm

It could be an avenue.

And take a look at some buffers too (at he same place):
http://www.muzique.com/lab/buffers.htm

Minion · January 22, 2009, 07:24:18 PM

I would use a low Value Well Matched resistor at each output , will will help share the output load more evenly between each output....

tackleberry · January 22, 2009, 10:59:43 PM

The jfet splitter from AMZ works really well.

Ben N · January 22, 2009, 11:29:23 PM

Quote from: goodoldpeachphan on January 22, 2009, 04:50:03 PM
Great! Thank you very much for the help. So it is just that easy? What about the cable capacitance issue... the capacitance of the cables going to the amp are summed in this case, right?

Only if they are going to the same amp--in which case, you don't need two cables, right?

frank_p · January 23, 2009, 01:57:20 AM

Quote from: Ben N on January 22, 2009, 11:29:23 PM
Quote from: goodoldpeachphan on January 22, 2009, 04:50:03 PM
Great! Thank you very much for the help. So it is just that easy? What about the cable capacitance issue... the capacitance of the cables going to the amp are summed in this case, right?
Only if they are going to the same amp--in which case, you don't need two cables, right?

Well seen !

goodoldpeachphan · January 23, 2009, 09:15:49 AM

This is excellent. Exactly the type of info I was looking for. Thanks on all accounts for the help guys!

Processaurus · January 23, 2009, 09:36:09 AM

Hi, the cable capacitance of the two cables, wherever they go, will technically be summed together (which the circuit will see as one (quite small) total capacitance to ground), but the only time cable capacitance is an issue for a guitarist is the cables between the guitar and the first electronics, every output (pedal's output) after that will have a much much lower impedance (like (470 ohms - 10K ohms vs the guitar's 250K/500K), so those electronics, by being able to source much more current than a guitar, can drive capacitive loads much better.

Go for the parallel jack, simple solutions are nice!

One thing that may be handy is to put a ground lift switch on the second output, to avoid ground loops between the two amps. That'd just be an insulated jack and a toggle switch in series with the sleeve connection and your multieffect's chassis ground.

goodoldpeachphan · January 23, 2009, 12:43:28 PM

Quote from: Processaurus on January 23, 2009, 09:36:09 AM
One thing that may be handy is to put a ground lift switch on the second output, to avoid ground loops between the two amps. That'd just be an insulated jack and a toggle switch in series with the sleeve connection and your multieffect's chassis ground.

I really like that suggestion, but wouldn't it be simpler to just not ground the second output? So long as I know which is which and only use the second output to run to a second amp if I'm using two amps, I'm safe with that setup right?

ashcat_lt · January 24, 2009, 02:42:58 AM

Does ground lift work at all with unbalanced signals? Won't this just create an open circuit where the second amp's input is concerned, making the cable into a large antenae to collect noise, but not to transmit the actual desired signal?

cpm · January 24, 2009, 03:56:33 AM

Quote from: ashcat_lt on January 24, 2009, 02:42:58 AM
Does ground lift work at all with unbalanced signals? Won't this just create an open circuit where the second amp's input is concerned, making the cable into a large antenae to collect noise, but not to transmit the actual desired signal?

i guess no if both amps share their ground

darron · January 24, 2009, 05:02:43 AM

i agree. i definitely wouldn't do it without eliminating the ground loop as you will very likely introduce unwanted noise. this is alright for bedroom but not for gigs.

if you are using a metal enclosure then it wouldn't be as simple as just not wiring up the ground on one of the output jacks, because it makes contact to the enclosure anyway and to all of the other jacks, so you'd need to isolated it somehow with plastic as suggested. small bear sells isolators, or you can just use a plastic jack.

and yes. of course the amps both connect to the same earth. as a matter of fact, my amps connect to the same earth as yours too!

goodoldpeachphan · January 26, 2009, 11:58:47 AM

Quote from: darron on January 24, 2009, 05:02:43 AM
i agree. i definitely wouldn't do it without eliminating the ground loop as you will very likely introduce unwanted noise. this is alright for bedroom but not for gigs.

if you are using a metal enclosure then it wouldn't be as simple as just not wiring up the ground on one of the output jacks, because it makes contact to the enclosure anyway and to all of the other jacks, so you'd need to isolated it somehow with plastic as suggested. small bear sells isolators, or you can just use a plastic jack.

and yes. of course the amps both connect to the same earth. as a matter of fact, my amps connect to the same earth as yours too!

I definitely get the part about using a plastic jack so that it's insulated from the chassis (ground)... But can't I just permanently leave the ground wire from Output jack 1 disconnected from plastic (insulated from chassis) output Jack 2 so long as I only use output jack 2 for when running a two amp setup? ...As opposed to having a toggle switch to lift the ground wire on Jack 2...

darron · January 26, 2009, 04:32:14 PM

Quote from: goodoldpeachphan on January 26, 2009, 11:58:47 AM
Quote from: darron on January 24, 2009, 05:02:43 AM
i agree. i definitely wouldn't do it without eliminating the ground loop as you will very likely introduce unwanted noise. this is alright for bedroom but not for gigs.

if you are using a metal enclosure then it wouldn't be as simple as just not wiring up the ground on one of the output jacks, because it makes contact to the enclosure anyway and to all of the other jacks, so you'd need to isolated it somehow with plastic as suggested. small bear sells isolators, or you can just use a plastic jack.

and yes. of course the amps both connect to the same earth. as a matter of fact, my amps connect to the same earth as yours too!

I definitely get the part about using a plastic jack so that it's insulated from the chassis (ground)... But can't I just permanently leave the ground wire from Output jack 1 disconnected from plastic (insulated from chassis) output Jack 2 so long as I only use output jack 2 for when running a two amp setup? ...As opposed to having a toggle switch to lift the ground wire on Jack 2...

yeah yeah. by all means. as long as you have one of them earthed. if you've got the space/time/cash i'd put in a simple spst or spdt to toggle the ground lift and the switch would just hookup between jack 1 earth and jack 2 earth. the reason being for any compatibility issues that you may run into in the future. if it's just for yourself and you're using it in you bedroom then if it works who cares? but if you're going to be gigging with it then there may be occasions where just using the one earth won't work properly. it's an interesting experiment also to hear what the ground loop noise actually sounds like when you toggle it. it can be subtle sometimes, but it annoys the hell out of me and you don't want extra noise on stage when the guy beside you already turns his distortion up way too high and doesn't gate it haha.

goodoldpeachphan · January 27, 2009, 10:45:31 AM

Quote from: darron on January 26, 2009, 04:32:14 PM
yeah yeah. by all means. as long as you have one of them earthed. if you've got the space/time/cash i'd put in a simple spst or spdt to toggle the ground lift and the switch would just hookup between jack 1 earth and jack 2 earth. the reason being for any compatibility issues that you may run into in the future. if it's just for yourself and you're using it in you bedroom then if it works who cares? but if you're going to be gigging with it then there may be occasions where just using the one earth won't work properly. it's an interesting experiment also to hear what the ground loop noise actually sounds like when you toggle it. it can be subtle sometimes, but it annoys the hell out of me and you don't want extra noise on stage when the guy beside you already turns his distortion up way too high and doesn't gate it haha.

Gotcha... I will at some point pick up the switch to do it right. No question ground loop hum is annoying... I used to just alleviate that problem by using a ground lift adapter plug on one of the two amps, but the switch on the effects box is definitely a much more elegant and "on the fly" solution.

OK, as my thought process continues on this project, another feature that I decided would be useful is an uneffected "dry" third output, not to run a third amp, but to have as an option for use with the second amp if I don't want the signal going to that amp to be effected. To accomplish this, would I just connect the hot and ground wires from the input jack to the third output jack? Or is there some more complicated element to this that I don't have the knowledge to foresee?

In case anyone wonders what I'm working on (I don't mean to make it seem like some top secret project), I've built four pedals myself now that I seem to fall back on exclusively... A BYOC Triboost, a Tonepad Rodent (vintage RAT clone), an BYOC EA Tremolo, and a General Guitar Gadgets AD-3208 analog delay (using MN3205 BBD's)... I've come to feel that these are the only pedals that I need to get MY sounds on a regular basis, so I've decided to rehouse them all in one clean grab-and-go analog multi-effects unit. I'm somewhat modeling the design/layout after the fuzzLab from Beavis Audio in that I'm going to leave all input/output jacks external so that the effects can be connected in any order, or other effects could be patched in at any point when needed. A couple other unique "features" are the ability to run two amps from it (as we've been discussing), that my Voodoo Labs Pedal Power will be installed inside of the unit, and finally I'm going to transplant my Peterson StrobStomp tuner into the box somehow... I'll post pics when the project is complete.

Thanks to everyone here for all the help! I'm a relative novice, and I really appreciate the guidance.

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How do I wire up dual output jacks on a pedal?