ABY Guitar Box




Intro: ABY Guitar Box

This tutorial was also posted in my blog. Check it out for more DIY projects!

This is a A/B/Y box. It acts as a switch. You can plug in a guitar and have it's output go into two amplifiers.
You can choose between the amplifiers or use both at once.
This is a very simple build. As a beginner I had only moderate work.

Step 1: Bill of Materials

Bill of materials:
2x 5mm LEDs
2x 4,7k Ohm Resistors
2x DPDT Switches (http://www.banzaieffects.com/files/images_detailed/d_4217.gif)
3x 1/4 jacks (P-10 jacks - http://www.effectsconnection.com/oscommerce/images/marshallstylemono.jpg)
Plastic container
9v battery clip (http://www.amqrp.org/kits/NCKeyer/elmer/P7190015a.jpg)

Tools needed:
Something that can drill, such as a Dremell
Soldering Iron & Solder

Step 2: Prepare the Compartment

You'll need a plastic or metal compartment.

There should be four holes on top (2 for the LEDs and 2 for the DPDT switches), one hole in front (for the input and two holes on the back for the output.

You could also have an extra hole for a 9v input plug but I didn't use one in this project.

Step 3: Electronics

Now for the fun part... connecting everything.

Follow the schematics available bellow. They are pretty simple.

The drawing was made with BEGINNERS in mind so it doesn't follow any conventions. I believe it is pretty self explanatory.

I tested everything out using a breadboard before soldering. This is a specially useful step for amateurs.

Testing the circuit.
invalid movie: http://vimeo.com/5571157

Step 4: Testing

Now you should have your A/B/Y box.

You plug in your guitar in one end and the amplifiers on the output ends.

By pressing the A/B switch you can choose between any one of the amplifiers as the output.

By pressing the A/B or A+B switch you can choose between using only one of the outputs or using both at the same time (that's the difference between A/B and A/B/Y box).


Testing the finished ABY box.



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41 Discussions


6 years ago on Introduction

i find it odd that the author didn't respond to a single question about whether his pedal has issues with noise. Perhaps i can help:

This schematic works, but has a key limitation, which can create noise issues in many cases. If it works for you, great. But, if you have issues with noise, the cause may be because the circuit doesn't ground the bypassed line. The solution to this is simple: use a 3PDT switch, instead, and switch the grounds, as well. If you are willing to do without the LED's, you can use the DPDT switch, still. The schematics to do this are widely available via a quick Internet image search.

The "Y" capabilities of any passive pedal, in which two guitars are routed into one amp, are suspect, in terms of avoiding noise/issues. In a pedalboard configuration, it may work if you have buffered pedals before the "Y", or if you are using active pickups. But, in most cases, the loading will cause negative interaction between the two instruments. The solution to this is to create an isolation circuit, and/or buffer the inputs, but this turns the pedal into an active one, rather than having the passive simplicity. That said, the schematics are some of the easiest to build, but will require some electronics/soldering skills. Another solution might be to use pedals that buffer the input prior to the passive "y". That whole scenario is kinda' hokey, anyway, though. Just get another amp.

For the people asking about the kind of wire, it really isn't a big issue... obviously, if you use a high-quality wire, it will, technically, be better, but, i doubt you'd hear the difference between Canare GS-6 (what i use) or solid-silver-core Teflon-insulated wire, and an off-the-shelf hookup wire. The gauge should probably be between 22 and 18.

2 replies

Reply 3 years ago on Introduction

Please upload a schematic for that design, as many of us have a hard time visualizing what to connect where


I want to build one of these to run two outputs from my guitar for recording - 1 to a mic'd amp / fx, and one clean line straight into a soundcard, so I am keen to reduce the possibility of noise when running 'Y'.
But I'm also a beginner.. any chance you could point me a wiring diagram for the 3pdt grounded version you're talking about?


alexanderm could u please show me how to make this pedal for two inputs and one output. I want 2 switch between instruments instead of amps... i'm a complete noob at circuitry etc and i cant find anything moderately easy on the internet on this subject :S pls help!

1 reply

Just plug the instruments into the "outputs" of the box, and the "input" of the box connects to your amp.
I know it sounds odd, but I guarantee it works.


6 years ago on Introduction

Hi, I get a huming sound on the output that is not on. Is there a way to fix this, or did I do something wrong?
Great instructable BTW. My first DIY project :)

ikasiliauskaswaka waka

Reply 7 years ago on Step 3

IF you preffer removing leds ( and i know this is a old post ) you can replace DPDT switches with SPDT switches simply leaving out the middle part. It'll function the same way, without the need for supply voltage nor the LEDs. Though I think you may have figured that one out by now :)


Reply 6 years ago on Step 3

I prefer to build it without the leds but I don't understand very well..Does it function without battery?? and then...if I want to use 2 amplifier together I have to put the switch on "A+B" but the Out signal isn't the same then the Input signal...right??..cause the impedance are in parallel..I think.. (sorry for the english but I'm an italian student )


7 years ago on Introduction

if you have a problem with "popping" sounds when you engage the switches, try putting a 1 meg resistor between the hot and ground of the jacks.


7 years ago on Step 4

One question, sometimes with these boxes, you get a "pop" when switching, is this the case with yours too?


7 years ago on Step 3

What gauge/kind of wires should I use? I've still not gotten around building this due to lack of time, and because I still need wires and the switches.


9 years ago on Introduction

hiya gcmartinelli, ive tried making this project but it didnt work, i am an absolute beginner so it was probably something ive done wrong, so i used the 4.7k resistor on just the LED (without the rest of the circuit) and the LED wouldnt light up, i was wondering if the resistors you stated (4.7kohm) are to high a value? like i said i probably have done something wrong but wanted to ask anyway.

5 replies

Reply 9 years ago on Introduction

Hi J-plan, maybe you soldered something wrong. I obviously built it and it works... :) The 4,7k resistors where alright because the voltage of the battery feeding them is high. I guess you could use a smaller battery and smaller resistors. Maybe you connected your LEDs inverted? I've received some LEDs with Anodes and Cathodes "reversed" (short legs on the wrong side). Hope you find the solution! Sorry I cant help much but I'm also a beginner!


Reply 9 years ago on Introduction

thanks for the reply, i took it all apart and started again, works perfectly, very happy with it, great instructable!!!! would be nice to see some more like this for beginners like myself. im currently working on a passive di box, will upload a instructable on that once im done, though the transormers to be used arent cheap :)


Reply 9 years ago on Introduction

Good to hear it worked j-plan! :) Thank you for the compliment. I'll try to post some more projects. What exactly do you think this Instructable had that others don't have (for beginners)? Maybe I stumbled on a recipe here... :)


Reply 9 years ago on Introduction

well its just that an AB switch is a very simple thing, perfect for a beginner like myself, i have since rewired the box slightly differently from yours:- i have wired the negative lead from the battery straight to pin 1 (sleve) on the female stereo jack, and then placed another lead going from pin 2 (ring) on the female stereo jack to the dpdt switch, this uses the jack plug as a switch so that the circuit is only complete when a guitar is plugged into it, by doing this you dont waste the battery by having the led's lit up permanently. obviously though, this will only work with a mono jack plugged in as the sleve of the mono jack makes the connection between pins 1 + 2 vand thus completing the circuit!!


Reply 8 years ago on Introduction

Does having the power run through the stereo socket creat noise or pop when you change outputs.