How do I make my own effect pedal / Passive Ring Modulator

Ollie94 · January 01, 2009, 03:00:09 PM

Hey!
I started circuit bending a few months ago, and I simply love it!
I have great respond from friends and musicians. But last week a guitarist asked me if I could make a effectpedal for him.
I have citcuit bent some toys and kids keyboards, but I don't know how to build a "Line In".
Are there some specific toys that you can rebuild in to a effectpedal? Ofcourse, I'l have to build in a jack, but thats no problem.
Big thanx!
Ollie94

Gordonjcp · January 01, 2009, 07:33:16 PM

It depends what you want the effects pedal to do. Things like fuzzboxes are trivially easy, things like harmonisers are incredibly difficult.

kick52 · January 01, 2009, 10:09:54 PM

You can order jacks, and switches etc from electronic component sites.
In/out jacks are exactly the same kit, just wired differently.

Gleix · January 01, 2009, 11:05:36 PM

http://experimentalistsanonymous.com/diy/Schematics/

This is a great website with schematics for... about any effects pedal you could ever want to build, but like Gordon said, some of them would be insanely difficult or near impossible to build.

Circuitbenders · January 04, 2009, 03:46:11 PM

Quote from: Ollie94 on January 01, 2009, 03:00:09 PM
I have citcuit bent some toys and kids keyboards, but I don't know how to build a "Line In".
Are there some specific toys that you can rebuild in to a effectpedal? Ofcourse, I'l have to build in a jack, but thats no problem.

I'm not sure you've got the right idea here. In order for something to process an external signal it has to have some kind of processing circuittry in the first place. You can't just wire a line in into a speak & spell or something and expect it to glitch the incoming signal. If something already has some kind of external input which it processes, like a voice changing megaphone, then its pretty easy to wire in a line input instead of the mic and use it as an effects unit. Theres plenty of info on how to do that on this forum. Digital delay units can also be good as circuitbent effects.

dimefan90 · January 09, 2009, 01:32:56 PM

i know you can mod a sega master system to be like a fuzz pedal. look up sega master system bitcrusher in google, i dont know how difficult it is though

Gordonjcp · January 09, 2009, 03:43:26 PM

Quote from: dimefan90 on January 09, 2009, 01:32:56 PM
i know you can mod a sega master system to be like a fuzz pedal. look up sega master system bitcrusher in google, i dont know how difficult it is though

I don't really see the point - it uses an Arduino to handle the sampling, which is more than capable of running some simple effects software *anyway*.

Bogus Noise · January 28, 2009, 06:42:24 PM

A lot of those toy voice changers can be modded into some cool effect boxes. Also, some toy keyboards have microphones that send the input to the speaker. If you get distortion points on those then you can put a jack inputs on them to process an incoming signal instead. I did that on an Early Learning Centre keyboard a while back, and put a ring modulator in there as well, it turned out like this:

http://uk.youtube.com/watch?v=eivaAGigubI

They also do a purple version of the same keyboard. Would be a bit of an odd shape for an effects box though

Block · February 17, 2009, 03:16:51 PM

Hey yes the voice changers are a definite hit. even without bending putting musical sounds through them instead of spoken word is great.

I've done just that to a buzz lightyear voice changer.
Worked a treat and had a resitor controlled frequency control that was easily modded with a pot and some touch points. Feedback/bypass is also a must have mod if you're going to use one as a standard effects pedal.

Loving the ring mod on that toy keybaord, is this something you can do to "unbendable" machines. I've got a few of those lying around so some tips on how you make a ring mod would be great, email me if you like

Gordonjcp · February 17, 2009, 10:36:56 PM

some tips on how you make a ring mod would be great

A ring modulator is also known as a "four-quadrant multiplier", because it can multiply one voltage by another (a two-quadrant multiplier would be a VCA). The crucial difference from a VCA is that if you apply a negative input voltage on one input, the other input is inverted.

The practical upshot of this is that if you put in a sine wave to the "carrier" input, the "modulator" input will get louder as the sine goes from zero to one, quieter as it goes back down to zero, and then get louder again but inverted as the sine goes negative. Do it at around 30Hz and talk in a flat clipped voice, and you are a dalek (don't try to do a funny robot voice, just keep the pitch steady and space - your - words - out - like - this, it takes practice). Do it around a couple of hundred Hz and you get clangy bell-like noises. Go up to a few kHz and you get weird aliasing-y effects.

Okay, so how do you make one? Well, the simplest way is a diode ring - hence the term "ring modulator", who'd have thought it? You can also use a kind of bridge circuit with a transconductance opamp, as used in a lot of 80s synths. The much-admired Korg MS-series ring mod really was an XOR gate fed from the squarewave outputs of the two oscillators.

Bogus Noise · February 19, 2009, 02:48:43 AM

I drew this up from an old issue of The Mix years back... I presume it'll be reproducable, it's not that unique a design

Costs something like a fiver to build and all the parts should be readily available. Germanium diodes are better, but they never arrived from place I ordered from on eBay, and they've gone quiet now.

You can add them to anything really. if there's microphone jack then wire that to the carrier, and if not (or also) build an oscillator to put in there as well. I like to make them patchable as well - if there's a ring modulator in there, you might as well make it openly useable.

Text from the magazine:

PARTS LIST

4 X 1n4148 diodes
2 x miniature audio transformer LT44 (Maplin code HX82D)
3 x 2.2 uF non-polarised capacitor
3 x mono jack socket without normalisation (has two tags instead of four)
Small amount of wire
A metal box
Superglue

BUILDING STEPS

The circuit diagram shows the construction in a semi-schematic and physical form. There is no need for the use of vero board.

1. Superglue the two transformers about 6cm apart inside the metal box with the three terminal sides facing each other.

2. Solder the diodes as shown in the diagram, taking care to get the polarity correct.

3. Solder the earth connections together and connect the earth to the metal box.

4. Make a connection between the earth wire and the screen connections of the three jack sockets.

5. Solder a capacitor onto each of the remaining tags on the jack sockets and connect the other terminal of the capacitor to an appropriate input/output wire on the transformers.

Circuitbenders · February 19, 2009, 07:47:38 AM

somebody give that man some karma!

computer at sea · February 19, 2009, 03:28:29 PM

Wild! I was just looking at a schematic exactly like this yesterday.

Signal:Noise · February 19, 2009, 06:47:07 PM

Bitching

sherbert mastodon · February 19, 2009, 06:55:49 PM

I keep meaning to get my hands on a voice changer... someday! (That said, I've got a ton of crap I've been meaning to bend, but haven't got round to it!)
On that, I remember someone in the Experimental Musical Instruments journal making a horrible reverb-type thing from a Skeletor's castle toy, which my neighbour had....