I know this is a bit out of the scope of this board but I thought I might get comments from some of the more DIY oriented fooger users out there.
It is rather easy to convert a resistance to a voltage using a bridge circult. But lets say that you open up a stomp box then find the potentiometers and replace them with a plug for a jack. this is an easy way to make any stomp box be controlled by and expression pedal although resistance might have to be added. Simple right?
But what if you wan’t to replace the resistance with a resistance source which varies based on a control voltage? Is there a circut to do that?
I’ve been very interested in thism. Having done a lot of circuit bending projects myself, it all depends on the pedal… there are so many pedals out there that it really doesn’t just vary from pedal to pedal but from parameter to parameter. As the increasing amount of pedals witch to digital control, unless its a higher end pedal i think a lot of control voltage users just assume go for the modular equivalent of such effect. For example trying to add cv to some vintage/boutique/sentimental stombox might be worth or even easy to convert where as a lot of conventional pedals and modern effects might be downright not worth putting the effort into. A lot of times effects with expression jacks are already working within’ the scope of your cv instrument. Here are a couple solutions i’ve seen so far.
obviously if your really interested in doing these extensively custom type of mods you might benefit from reading about pure data or max/msp and the arduino chipsets where you can easily use your computer to interface your synths/cv/midi/osc with not just stompboxes but any type of circuitry
Im not an expert, but as the guy above said, it really depends on the pedal, and generally I think its pretty tough to do, even on all-analog pedals. My experience has been this:
I contacted Howard Davis about the potential for adding CV inputs to my EHX Polychorus, and was told that the ‘resonance’ could not be CV driven, only by 50k linear taper pot, and I could get voltage control over the manual sweep, but it would need roughly 12v+ for a full sweep…(and would take a significant amount of time, relative to the value of the pedal). If you were doing this yourself, then obviously an hourly rate is of no issue, but even then you may find issue achieving the necessary control voltages- certainly in my case, the CP251 and MP201 would not be adequate to control the Polychorus if I had that modification done. Ive also had luck with quite a few exp inputs that were scaled well for 0/+5v.. so I dunno.. ymmv!
I am in the middle of modding my Pigtronix attack sustain pedal. I have the Envelope jacked out and the Envelope In as well, but it is using a range of 1-12.8vDC for control voltage. This means I have to limit the output CV and build a circuit to boost a 5vDC CV signal to be useable for the VCA input.
I haven’t used them, but Vactrols seem to be a great idea for controlling resistance (like the Square wave Parade circuits).
Thanks for the great posts here? I like the CV to resistance boxes and the schematics don’t look that complex either. Certainly, a potentiometer can be replaced with any resistance sounce but that is not really what we are talking about her technically. The pot is really being replaced with a circut and that may be the reason for the comments your friend made about the Polyphase.
If I can do something simple, I would. I know enough to replace a potentiometer with another source but not enough to understand the complexities of the circuts. If I did anything it would be more an experiment and done blind in a sense.
It would seem that all things lead me to a modular although I don’t even know if there is a module to do what the Polyphase or Flanger Hoax does. I can tell you that I love analogue circuits. I have a digital synth and a Voyager and I love both for different reason but there are no suprises with the digital synth, it just runs a program.
My foogers and Voyagers do things that often suprise me. I have frequent “oh, I did not know that was going to happen” experiences and that’s what makes them interesting. Hopefully some of the world of stomp boxes and modules can come together and a new terrirtory of sonic mahem can become a reality.
Just to clarify, Howard Davis isn’t a friend of mine, but a well known builder who has created a score of effects for EHX and Pigtronix, including the Polyphase.
For CV flangers in pedal form, there aren’t many options, they’re all discontinued and expensive, but check the Paradox TZF (which inspired the Hoax and its through zero flanging) and the Lovetone ? Flanger; limited CV controls, but they’re top notch. The TZF goes farther than the Polychorus and is much higher fidelity… just stunning. I’ve only had it a few weeks, but the Polychorus is on the sidelines for good.
I too bothered Howard Davis for some assistance adding cv to my pigtronix echolution and got pretty much the same response. I also asked him if he could help me create an external audio loop, which he didn’t feel would be easy enough but i still really want to do!
as for stompbox flangers with cv you mentioned the good ones, there are a lot of 80’s rackmount (even modular) flangers that except cv, here are a couple off the top of my head:
some old eventide, mxr, vestax, and well there are all kinds of cv friendly things out there you just need to do some deep down research. But if your really waiting for something simple the old school ada flangers are to be reissued. They are highly praised and should be released fairly inexpensively.
You should really just search around… this has been done many times and i’m pretty sure its been documented more than once…i tried finding some of those links but my bookmarks are such a mess… I found this in the process though!
In general it looks like finding someone who is willing to offer their services for adding cv in/out’s to a predetermined/tested group of pedals using vactrols or maybe other methods is what some are looking for.
I think we could create a pretty comprehensive list of cv friendly stompboxes and modification/interfacing resources, and this might be a good place for that list seeing as the the moogerfoogers caused this big switch to cv controlled stomp boxes, and a lot of people come around here looking for tips on utilizing cv. I think i could do a pretty good job myself and when i get a little time i will probably start it… but is anyone else out there interested in helping?(or know of a comprehensive list existing already)…there are so many pedals out there and sometimes the only way to really know what features they offer is to know from experience.
The Paradox TZF sound incredible. This one got my eye and not many stomp boxes outside of foogers do that for me so thanks for the recomendation. Why I really want CV control, this one might add some nice movement.
The samples were almost all guitar with the exception of some pink noise experiments but I would love to hear what it can do with a Voyager or for that matter, other foogers like the delay.
Another idea also jumped into my mind which while a bit unorthodox have possiblities. A long long time ago, when I was getting myself first guitar, amp and stomp box (a Small Stone believe it or not), I was immediatly thrown into the seedy world of gear lust. Along with looking at the EH catalogue with dreams of expanding my collection, I noticed that they had something to turn knobs remotely. That combined with a servo motor and you have a more mechanical way of controlling pots with CVs.
There are also remote control pots which can replace those in a stomb box although I don’t know how you get from CV to IR signal. Perhaps as complicated as the original problem.
One other possiblity is simpler. A vactrol. It is an isolator so all that is connected to the stomp box is a photocell. Some careful computation and perhaps another resistor might be necessary but this might work.
The Arduino is also programmable so there are lots of possiblities here for sequencing pot changes in stomp boxes provided one takes a bit of time to do with wiring but its pretty simple stuff expecially with a breadboard.