#1
I'm new to DIY mods and need a push in the right direction.

I'm wondering if I can make an ABY box (1 input, 2 output) that will allow me to transition between the two outputs with an expression pedal. Would this need to be passive or active electronics? Are there any schematics out there that could get me started?
#2
I had an idea for this.
You would have the signal split to 2 outputs ( "y" mode), and before each output there would be a passive volume potentiometer. The foot pedal would have the fulcrum in the center of the pedal (as opposed to the heel), and by rocking to one side, you'd increase the volume (technically decrease the resistance of the pot) of one output while decreasing the volume of the other output.
Just an idea... idk if it'd work. I'd love to know if it would, though.
Schecter Gryphon; Ibanez AEG20E
Peavey Rage 158 ; TRAYNOR YCS50
EHX Big Muff Pi; Dunlop CryBaby GCB-95 (modded); MXR M-108 10-band; DigiTech JamMan Looper
#3
hmm, i think there is something out there that does that. i think there are stereo volume pedals that do that kind of thing.

i cant think of any good way to do that completly passively. any good y-splitter is going to have some sort of powered buffer to keep signal levels even. i would basicly have something that split the signal into an A and B path to start, so a y-splitter. then have each go to a volume pot that is connected to the footswitch, but they would be turned opposite ways by the treadle.
#4
Quote by BD 425
I had an idea for this.
You would have the signal split to 2 outputs ( "y" mode), and before each output there would be a passive volume potentiometer. The foot pedal would have the fulcrum in the center of the pedal (as opposed to the heel), and by rocking to one side, you'd increase the volume (technically decrease the resistance of the pot) of one output while decreasing the volume of the other output.
Just an idea... idk if it'd work. I'd love to know if it would, though.

Or you could get a standard wah shell to turn a dual-gang pot, where one gang is wired in reverse.
#6
Quote by Invader Jim
Or you could get a standard wah shell to turn a dual-gang pot, where one gang is wired in reverse.

oh man, just thinking of ideas that would incorporate that is giving some horribly awesome plans. like an overdrive where you set an internal level and then have a dual gang pot that controls both gain and level in opposing directions. clean boost to straight pedal od with the rock of a foot. phaser where you can control both rate and depth like that. the possibilities are insane...
#7
I'm not sure, but, Is this what your looking for?


You would just eliminate the C out, and switch the SPDT switch, for something else. I think Jim said what it was.
..I was watching my death.
#9
Quote by Invader Jim
timbit, that's not a passive circuit. TS wants a passive circuit.

Jimmy: you have given me an idea...


Ah, I see. I just skimmed through the posts very quickly.

Take out the buffer then. Not sure if that makes it passive though...
..I was watching my death.
#11
taking out the buffer would make it passive, but then the problem becomes that the signal is loaded differently on each side. which kinda messes up things as i understand it. i mean ideally you would want to isolate the outputs of the two amps (reduces hum) but there are simple passive ways to do an A/B/Y switch.

but hey, you could just go super simple and run input to the center lug of a pot. then each side is connected to a separate output. at some point in the turn of the pot, the input should see similar loads to either side and be split fairly evenly. turn the pot one way to reduce the load and increase signal flow to that side. i dont know how well it would work, but i guess its worth mentioning.
#12
Quote by Invader Jim
Taking out the buffer will just render the pedal useless...


Really?
I didn't think it would.
That op-amp buffer just boosts the signal, as I have come to believe, allowing the 2 outputs working at the same time.

I just figured out what the ts wants. It would require a buffer of some sort to equally boost the signal. He want's both of them to fade into eachother, or something like that.
That clears things up for me.
..I was watching my death.
#13
the op amp is running as a buffer, it shouldnt be boosting anything. basicly the point of it is that what goes in is exactly what comes out, no matter what kind of load is put on it. so signal into two buffers would split evenly since the buffers are the same. then the outputs of the buffers are the same as the inputs, so that means the signals are split evenly. otherwise if you turn off one switch you get a different load than if it was on and the signal can do wierd stuff and have volume fluxuations.

i hate trying to work with buffers though, they always confuse me. half the time i just throw a bunch in and hope im isolating things enough. which is why i love PSpice, testing designs makes things so much easier.
#14
Quote by jof1029
but hey, you could just go super simple and run input to the center lug of a pot. then each side is connected to a separate output. at some point in the turn of the pot, the input should see similar loads to either side and be split fairly evenly. turn the pot one way to reduce the load and increase signal flow to that side. i dont know how well it would work, but i guess its worth mentioning.

Well, that's kinda how output blenders in some guitars work.

Though that may not transfer well to pedals..
#15
You talk about Spice quite abit... What is it?

That signal going in, is the the same as going out thing, was what I was trying to get at.
..I was watching my death.
#16
Quote by Invader Jim
Well, that's kinda how output blenders in some guitars work.

Though that may not transfer well to pedals..

yeah, thats kinda what im thinking. it would be super simple to do, and i never think simple things are going to work. i wish i had some spare jacks lying around, id wire one up and see how well it worked. probably not well, but worth a try if anyone has the parts and a couple amps.


EDIT: PSpice is a CAD package (computer assisted design) that allows you to make circuits and run things through them. its got models of a lot of components, and better packages actually model specific transistors and diodes and such. you can edit some properties so that the op amp or transistor or whatever has similar specs to what you are using though. so then you build your circuit and you can run a bunch of different types of simulations on them. some just test the DC properties, some will look at output over time, some over frequency. i used to have a better program called ADS that was awesome because of all the stuff i could test and work with.


but basicly its just a way to model circuits on the computer and for some stuff its quicker than building it to see if it works how you planned.
#18
The problem with the Ernie Ball volume pedal is that when the treadle is centered, both outputs have less volume. I hope that makes sense. It's not a smooth transition from A to B as there is a large volume dip in the middle. This project will probably have to have active components.

I have a Fender Volume/Tone pedal that has a the traditional volume pedal Y axis and the top swivels for an X axis. It has one input, one output and a tuner out. I've already had the swivel portion modded to be a TRS expression jack that replaced the tuner out. I paid a local custom shop to do it, so don't assume I know anything about the actual work that took place. I just come up with ideas. I'd like to start doing these things myself, though.

Now, I'm thinking of replacing the expression with a B output and installing an panning device. I really don't know the pitfalls of any of the above suggestions and am a bit intimidated by active components. I've done plenty of small passive mods to my instruments. Soldering isn't a problem.
#20
Quote by Sabicas
Hmm, can someone who reads schematics determine if this will do what I want?

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

It says it can be used as a splitter or a mixer. Can't a blend knob be replaced with an expression jack?


You can't read schematics? Check out the FAQs, or the Ultimate Wiring thread(not sure which one).

Theres a link, actually, I believe I have it in my favorites.
Ahh, ****. Where is it?
Well, that's strange. I did a search on UG, and went to those threads. Damn, I can't find it.

EDIT: Theres this
http://www.diystompboxes.com/pedals/FAQ.html
Still looking for the other. I wish I had favrited it.

EDITx2: I can't find the other one, that I was looking for. I downloaded the symbols and everything from that site.
However, I did find this
http://www.falstad.com/circuit/
It's a simulator. Should help you understand circuits better.
..I was watching my death.
Last edited by timbit2006 at Jul 20, 2009,
#21
Quote by Sabicas
Hmm, can someone who reads schematics determine if this will do what I want?



learn how to read schematics. it'll be awfully difficult to build this without knowing how to. the beavis site has a good writeup on how to read schematics.
#22
Quote by Sabicas
Hmm, can someone who reads schematics determine if this will do what I want?

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

It says it can be used as a splitter or a mixer. Can't a blend knob be replaced with an expression jack?

while yes, you could replace the blend knob with an expression jack or just put the whole thing in a wah enclosure and use it like that, it will not do what you want.

to start, it is not passive (which is probably not really that feasable anyway). then what the thing does is blend two effects loops into one output. so it is like mixing a chorus pedal with phaser each on the dry signal, so they come together to go to your amp.

now it may work if you stick the wah pot on the front end, but then again im not really sure. heres a schematic (modifying the one from ROG) of what im thinking. im going to see if i can model it later today.
#23
Tried out the above idea and it didnt really work well. had to add a capacitor to ground on either side of the pot to get it to do anything, and then it wouldnt turn all the way down. the output level would not go all the way down when the pot was turned in one direction, would only go to about half. i suggest taking out that blend pot, then replacing the two 1M resistors by the outputs with a dual gang pot. so that way when the one is turned down it sees high resistance to ground and the signal goes out, but the other sees a low resistance to ground and is shorted. turn the pot the other way and the situation is reversed
#25
bespeco or somesuch make a cheapo stereo one that can do it, I think...

if not, you could customise a mono one to do it for you with little hassle, whether it's wiring the current pot with all three lugs going to the three connections of a stereo jack (or to two mono jacks). or with a dual gang pot.

I might try it at some point!

i'm really tired justnow though, something tells me doing it with a single (gang) pot wouldn't work but I can't think of why...
Last edited by jimRH7 at Jul 20, 2009,
#27
I've decided not pursue this project any further. I'm planning on using a stereo setup where each pickup has it's own independent output and a blend knob is used to pan those outputs. It may have the same problem as the Ernie Ball pan pedal, but I'll just have to live with it.

Thanks for all the of suggestions.