Hello, I did a quick search on my question and couldn't find an answer. Forgive me if my question has been asked a million times daily.

I am going to mod my Fender Stratocaster with the PCB from either a EHX Muff Overdrive (the small version), or the EHX Screaming Bird. Both pedals have a fairly tiny PCB that I am confident I can rout enough space for without too much work, and both pedals only have one knob + the footswitch as controls. I don't want to use the stomp-ON/OFF-switch to activate the overdrive. I was wondering if it is possible to instead activate the effect with a push/pull pot (to be located where my second Tone control is on my Strat). I looked at the PCB (there's a short vid showing the guts of it here http://www.ehx.com/products/screaming-bird), and I'm a bit confused as to how I would go about converting the normal pot on the pedal's PCB into a push/pull pot that would activate the effect when pushed/pulled/whatever. I'm mostly confused about how to eliminate the pedal's original on/off mechanism (the stomp-switch) from the circuit and simply use the push/pull pot to activate it. If I put in a push/pull pot, would that over-ride the stomp-switch? I know a bit about electronics, but not that much, so any help would be appreciated!

Does anyone have any experience trying to do this?
there are push pull buttons arround you could use, simply replace the stomp button with push/pull, errm check out axesrus.co.uk they have stuff like. shouldn't be hard simply re soldering the wires on the push pull button hope this helps
Thanks for your reply Owen. To be more specific, if you'll notice on the Screaming Bird's PCB (http://www.ehx.com/products/screaming-bird), for example, there is a normal 'Boost' pot (the only knob on the pedal), and then a metal footswitch to activate the pedal. My question is: Is there a feasible way to activate this effect using a push/pull pot that ALSO controls the 'Boost' when you turn it? I'm starting to think that it's a lot more complicated than it sounds and would require a lot of skill to re-wire it.

Edit: Another question: If I re-soldered a push/pull where the normal pot is currently, and then activated the effect that way, could I just leave the metal stomp-switch disengaged and it would be like it wasn't even there?
Last edited by Rehearsalpro at Jun 6, 2010,
err yeah theres dual function switches ive seen arround which are push pull (for turning it on and off) and you twist them for boost control in your case, not sure where i seen them but err they are arround, what about something like the distortion switch here http://www.axesrus.com/axeElectronicsEffects.htm 3rd down that would do the same thing, but sound might wont be the same, i suppose its so cheap its worth a shot hope this helps
if this is going into a strat, I'd wire your middle tone as a master tone and then replace the 3rd knob with the push/pull. The 3rd knob would act as the pedal's pot and the switch to turn it on, just to clean it up a bit. I can draw you a diagram if you can get a schem of the pedal up.
Ice, yes that was the plan, to make a Master Tone and then use the other Tone knob as the push/pull control for overdrive effect (push/pull and activates/deactivates). I will see what I can dig up for a circuit diagram of the pedal. I have included a screenie of a video that shows the circuitboard. You can see the pot in the middle of the unit, and then the metal stomp-switch dangling from the bottom. In a nutshell, is it feasible to somehow get rid of that switch completely, leaving the push/pull pot to perform both activation and adjustment functions? Is it even necessary to get rid of the stomp-switch? Sorry for being a noob, I know these questions about onboard-effects get asked a lot because it's very trendy and whatnot, but I am genuinely interested in this specific mod.

Worse comes to worse, I will just install the overdrive effect as it is, using the existing metal stomp switch to activate it, and a separate pot to adjust it.
The challenge you are going to run into is having enough poles on your switch. Count the poles on the bottom of the stomp switch (my guess from the screenie is that there are 3 rows of 3 contacts). If so, then it is a 3-pole-double-throw switch (3PDT).
A push pull will only have 2 rows of 3 contacts double-pole-double-throw (DPDT). If you no longer want the LED, then you can can replace the stomp with a push-pull pot.

However, if you want to replace both the stomp switch and some other switch with a single push-pull, well that cannot be done.
You shouldn't need the LED indicator since you can just look to see if the switch is up or down, lol. I think your biggest problem here is going to be 1, getting the push/pull in place of the original pot within the circuit board and 2, getting it all to fit in the control cavity where you want it.
Ok, so bear with me here. You're saying I will have to replace the stomp-switch with the push/pull (sans the LED)? As in I will physically be putting the push/pull pot where the stomp-switch is currently dangling from? If that is the case, what happens to the original pot in the middle of the circuitboard? Will it not function? I'm sorry if I misunderstood you.
"However, if you want to replace both the stomp switch and some other switch with a single push-pull, well that cannot be done."

Thanks Cedric, that's pretty much the answer I was looking for. I think I will just install the circuit as it is, and drill an extra hole for the stomp-switch. Thanks very much for your help!
ok chief here's what you do. its very simple. no offense, but it seems you are making this harder than it actually is.

1. get a push-pull pot of the same value as the pot on the circuit board.
2. Remove the pot from the board and wire the push-pull's pot section in place of it. use wires as long as you need.
3. remove the switch and wire the switch section of the push-pull in place of that. You wont be able to use the LED. use wires as long as you need.
4. install into the guitar.
Cool, ok so I need to somehow un-wire the stomp-switch, and re-wire the on/off terminal of the push/pull to where the stomp switch's on/off was previously wired? I've never re-wired a stomp-switch to something else before, so I don't really know which terminal corresponds to what. Thanks again for all your help, this is great advice!
a push-pull pot is a DPDT switch and a pot. The shaft is the switch actuator and rotating it controls the pot. same pinout of the stomp, only with 1 less column of lugs. look up a diagram of 'true-bypass switching' and wire the switch that way..

go to radioshack. there are tons of switching options in thier bins in teh back. push pulls, buttons, switches of all sizes.

you could easily drill a small hole on the pick guard and put a mini toggle switch in there
just found this for you:

If you rip out the old pot, wire in a push-pull pot in exactly the same way on the top bit. Then, rip out the old switch. It should be wired in a similar way to the diagram. I believe if you wire it up the same way, but omitting the purple wire and the LED/resistor it will work, but you will not have a LED to show you if its on. (can someone else make sure this is correct please!) But if you were going to look down at the LED you can just look at if the push-pull pot is up or down, so that doesnt matter really. If you particularly wanted a LED, then it cant be done with a push-pull pot.
Also, the input jack should be omitted, and instead the wire from the output of the master volume should go to the switch, in the middle on the diagram but on the push pull it should be on the left hand side, middle lug. You should have a stereo jack installed as the output of your guitar, solder the 9v ground to the ring on this instead of the ring on the input jack. Afraid to say that im not sure about the ground wires, as there are two ground points on the PCB in the diagram, hopefully someone else can help with that.
Hope this helps!
Quote by minnis
I believe if you wire it up the same way, but omitting the purple wire and the LED/resistor it will work, but you will not have a LED to show you if its on. (can someone else make sure this is correct please!)


Quote by minnis
If you particularly wanted a LED, then it cant be done with a push-pull pot.

yes it can, but it involves building a little circuit, which i dont think TS is capable of yet. See this article: http://www.geofex.com/article_folders/millenium/millen.htm
Thanks a ton, Jim and Minnis! Both of your explanations were very helpful, and I appreciate the diagram. I see now that it is a pretty simple concept. Just a few re-solders, nothing I can't manage, I hope. I will be buying the effects unit and the push/pull pot next week, and I will post some pictures/video to show you guys how it turns out. Thanks again for all your help!
Quote by Invader Jim
good luck, chief.

Let us know how it turns out!!
One last question, would properly shielding my Strat (with copper tape and proper star-grounding) help reduce noise caused specifically by whichever booster/OD pedal circuit I decide to install on-board my guitar? Does shielding reduce only the noise caused by the guts in the guitar itself, or also reduces noise potentially caused further down the effects chain beyond the guitar itself?
shielding only reduces outside sources of noise hitting the guitar. it wont affect the pedal chain. whatever noise your pedalboard picks up gets to the amp. most pedals are encased in thick metal shells that are grounded in the pedal's guts so that in and of itself is a great shield. if the pedal still picks up noise then, not much can be done.

if the pedal is in the guitar, it is 'protected' by the shielding. but the 'protection' stops at the output jack.

(i use the word 'protected' loosely since noise is harmeless to the gear but i think you see what i mean by it)
Ok here's an update finally. I decided to scrap my plan to install the Screaming Bird and instead bought an EMG After Burner onboard pre-amp, which is essentially the same thing in a much neater package, and tailor made for this type of mod. Anyways, I have it all wired up but I have a few questions:

I am attempting to do the 'Master Tone Control' mod for my Stratocaster as well. I have taken out the middle control pot (which is where the EMG Afterburner is now), and I re-wired the other Tone Control pot just like in the Seymour Duncan wiring diagram below.

Question 1: When I opened up my Strat, the capacitor on the last Tone Control pot was wired from Terminal 3 to the back of the pot. However, in the diagram below, it shows the capacitor should be wired from Terminal 2 to the back of the pot. Does this make a critical difference when performing the Master Tone Control mod?

Question 2: Currently, I have a wire connecting the back of the Master Tone control pot to the back of the Volume control pot, like in the diagram below. All other grounds are connected to the back of the Volume pot as well. Does this in any way create a ground loop problem? If so, how should the ground of my Master Tone control be connected?
It's me again. I have completed the installation process for two mods: The EMG Afterburner replaced the middle tone control, and the other tone control is now the Master Tone Control. I installed the battery right underneath the output jack by the way. I flipped the output jack cover the other way, to accommodate the battery. Looks a bit odd, but it beats routing the guitar and ruining it.

The EMG Afterburner sounds excellent! It provides a very decent amount of overdrive on its own, and when added to an overdrive guitar amp, the results are exactly as desired. I have noticed hardly any additional noise even when the Afterburner is engaged and fully dialed in. I have yet to try adding it to an already highly distorted guitar amp, so I cannot attest to whether or not it will make your guitar squeal uncontrollably. On the clean channel, it overdrives the amp nicely, in a natural way. It is a very versatile gain boost that will give you everything from a slight bump to your signal, to a silky smooth overdrive/distortion depending on what you are pushing with it. I would recommend this to any guitarist that likes a little to a lot of dirt in their signal. The boost can sound very significant especially on the clean channel, your volume will go up quite a bit louder when cranked.

The Master Tone control mod seemed to work like a charm. I'm not sure whether or not the capacitor that is currently installed is the optimal rating for all 3 pick-ups. Is there a capacitor in particular that suits all 3 pick-ups nicely? Or does it not really matter? I'm not that picky about my Tone control, I am just wondering.

Overall, I feel like my guitar is much more versatile. I enjoy the ease-of-use. Having more gain at your finger tips is always a good thing. I no longer feel like my Tone controls don't do anything, as I have replaced them with a gain boost and a master tone control, both of which, in my opinion, are much more useful than the 2 stock tone controls on a Strat. Another benefit to this mod is that it converts your high impedance guitar into a low impedance guitar, allowing you to drive long effects chains, and maintain a clearer/stronger signal in general. If you have $50 to spend, I recommend purchasing the EMG Afterburner, it's perhaps the best guitar purchase I have ever made, no joke.