I've been working on the geofex frobnicator for a few months now, but I can't seem to get the damn thing to work. I've looked around for another ring mod project but haven't seen any. Anyone know of one?
you can try this (+12 -12 supply) (down on the left :)
mos 4011 based very simple
(http://www.sequencer.de/forumsynth/simplesynth/simplesizer_base/VCFVCA.JPG)
this is on my workbench... not tried yet...
If you can get hold of a copy of "Practical Electronic Musical Effects Units" by R A Penfold there is a good one in there called a "Metal effects unit". You might be able to get a copy of the book at your local library or pick one up cheap off e-bay.
This was one of the first pedals I built and as a result I used 3 separate bits of stripboard for the different parts of the circuit. I wouldn't do that now as it's like rats nest in there. It gives a very stong effect and you can also get some deep tremelo like sounds out of it if you use the sugestions that Penfold makes.
I fyou want a really good ring mod, I advise using the AD633 from Analog Devices, but it needs a dual power supply.
If you want to avoid bleedthrough of the carrier, it's very difficult.
The chunk shown in the simplesizer circuit above, is not really suitable (for most applications) because, it is operating digitally (that is, the signal woud have to be converted to a square wave at the input & then multiplied by a square wave carrier. Pretty rough!! and, no harmonics...
For a classic transformer style ring modulator, Ken Stone sells a board (with transformer and matched diodes) http://www.cgs.synth.net/modules/cgsrr.html
I know Ken personally, and I can vouch for his boards - but they are for synths, which again means dual power supply & extra circuitry to get the guitar signal boosted up.
Isn't the transformer diode ring ring mod passive? This could be run from a single sided power supply?
the passive ring mod is passive, so no supply is neccesary. it's just that:
a) you need to amplify the signal a good amount for a guitar on the input or you'll barely be able to hear it
b) you may need to amplify again on the output because of the volume drop from the circuit
c) you'll need to use a carrier signal - either an internal osc (extra circuitry) or a carrier signal (which will also need to be appropriately amplified)
d) also, match the diodes for the least bleedthrough
that beng said, i've had problems when attempting a passive ringmod project. i built it stock and it worked fine (i was using it with my ipod as carrier and a keyboard as input). but i attempted a bigger project (twice!) and had many problems, even with simply adding a sho boost before input and carrier. then with adding opamp boosts. maybe my jacks were wired incorrectly? i don't know. but things were weird... :P
I understand the passive ring mod needs a strong signal to push through both coils and the diode ring. I guess I was suggesting it could be run from a single sided power supply.
QuoteI've been working on the geofex frobnicator for a few months now, but I can't seem to get the damn thing to work
Ahhhh. The LFO tends to "lock up" if given too much voltage. It seesm to prefer Vsupply of around four times the Vf of the LEDs. Usuually, this is about 8 and a bit volts, so try putting two regular diodes in series with the supply. I've built several ring modulators and like the frobnicator.
You might also try my simple balanced modulator. It sounds virtually the same as a ring modulator. Here are the details:
(http://www.aronnelson.com/gallery/d/17571-1/Modulatron+sch.jpg)
(http://www.aronnelson.com/gallery/d/17572-1/Modulatron+pcb.jpg)
(http://www.aronnelson.com/gallery/d/17574-1/Modulatron+overlay.jpg)
And here's a link to a build report in the forum - http://www.diystompboxes.com/smfforum/index.php?topic=33454.0 (http://www.diystompboxes.com/smfforum/index.php?topic=33454.0)
cheers
Brett is right, that's the basic "fix" for the Frobnicator and is included in my built report from some while back.
( when I didn't have a clue what I was doing ! )
I did get mine working too and it makes for a wicked tremolo also !! ... I've built one other since for a mate and that
worked very quickly with no problems .
MM.
The ring frobnicator problem was totally beating me....
Nothing would make it work. In total frustration I tried a different battery and it worked. I was lucky that the second battery was reasonably flat.
good luck !
Maybe in the Ring Frobnicator, using a different op amp would stop the problem.