HISTORY / INFO:
My seventeen circuit bending project started out its life as a Halloween
voice changer that I found at Marc's (a discount store and grocery). It cost me
a whopping $3.99. Actually, I bought two. It has three modes: monster, alien and 'own'
which basically means amplify. It takes 3 AA batteries to operate.
With the DJ Studio v2.0, I had toyed with using a tape player to make a distortion pedal. I met that with limited success, but had alot of fun doing it. I then started looking into bending one of the 3 Touch N Tells that I had, but quickly lost interest after spending a day or so trying to map out the touch membrane (only to find that sailormouth had done the work for me ahead of time!). So, I was looking for something that I could finsih quickly. So, I went with turning a voice changer into an effects pedal.
The experience wasn't too bad, I was really hoping to be able to tie into a pitch resistor for both the monster and alien modes, however, it appears that they are embedded in a dreaded black blob (1 of 2 in this toy). So I found a couple other mods and called it a month (it takes a while when you can only devote an hour or two here and there).
The biggest problem I ran into was figuring out the slider switch that made it all work. I knew I was going to re-house it, so using the slider switch wasn't going to be possible, especially since it was a side mounted one. The switch itself was a DP4T which was attached to another small board. I used my multimeter to figure out what all was connected to what when it was in each of the 4 positions (off, monster, alien, amplify). It was an odd little switch. In order for it to be turned on 3, not 2, wired needed to be connected to each other. Additionally, the default mode was the alien voice, not amplify. This was done so that a single test switch could be used to 'demo' the voice changer in the store.
The next biggest problem I had was after I had soldered everything and put everything in its new case, a Nascar promotional tin from Kraft Velveeta which cost me 50 cents. I plugged everything in and got... nothing. Long story short, while I had made some attempt to shield the 1/4" in and out jacks, I wasn't careful enough the first time. The jacks themselves were touching the metal tin and therefore hsorting each other out (or something like that). I solved this by putting electrical tape around the edges of the holes for the jacks. Voila, it worked.
By default, the thing has a tendancy to overdrive itself. I tried to put some resistance on the input and end added a 'gain' modification, but no matter what I did, the input stayed pretty hot. There is one mod which, somehow, bypasses the amplify part and makes it sound normal.
PRE-MODIFICATION PICTURES:
MODIFICATIONS:
1) Rebuilt on / off switch - I changed out the DP4T swider switch for an on/off toggle
and a SP3T rotary switch (amplify, monster, alien)
2) 1/4" input jack - I replaced the mic with a 1/4" mono jack. I believe that I put
some minimal resistance in, but the input still comes in very hot (ie, LOUD and DISTORTED!).
3) 1/4" output jack - I replaced the 4 or 8 ohm speaker with a 1/4" jack.
4) 'Normal' mode - When this toggle is turned on, it bypasses all the amplification circuits
and actually sounds normal (ie, no distortion).
5) Hi Band Muffle - This bend consists of a toggle and a 3 way rotary switch. Utilizing
different values of capacitors, each setting cuts down on the ammount of high end. The
'highest' setting turns everything into a big muffled mess.
6) Hi and Low Digital Noise - Consists of an on / off toggle and a low / high toggle. Somehow
it turns the signal into a digital sounding mess
7) Amplify Momentary - When the voice changer is in alien or monster mode, tapping this
button will put it into amplify mode
8) Gain Pot - I'm not sure of the resistance on the potentiometer I used. I _do_ know that
it was a 250K pot to begin with, but I then bridged the leads with somewhere around 50K of
resistance, effectively turning it into a 50K liner pot. Anyways, this adds some resistance
on the input. The amp section is picky and if the signal isn't strong enough, it just
doesn't amplify at all, so as the gain goes up (or down as the case might be), the sound
starts to cut in and out, only playing on really strong signals.
POST-MODIFICATION PICTURES:
front view
SOUNDS:
aye-nascarumba.mp3 - Me fiddling with the
effects pedal while listening to The Eagles. It's what I used when testing out bends and
it just seemed to, well, be in the CD player when I recorded. Bends are as follows: amplify,
monster, alien, normal, momentary amplify, 3 filters, low / hi digital noise, gain.
FUTURE MODIFICATIONS PLANNED:
Probably nothing. I still have another one to bend. I may take another crack at it,
but focus less on pfinding a pitch bend and more time probing with various components
(diodes, capacitors, coils).
Last Modified: April 25, 2006