Stair-stepped Expression Pedal?

[fu22ba55]

I've got a pedal with an expression input, and I'd love to fiddle around with an expression pedal, but I have one problem:

I hate the sound of expression pedals.

They always sound too human, too wanky, too "wah wah"... it always comes back to that damn wah-wah type of foot motion.

Is there any way to mod an expression pedal to "dehumanize" it? Instead of it being a smooth linear change, could it be stair-stepped so it would abruptly change values for more of a digital, glitch sound?

The values would not even have to be linear (increasing or decreasing.) It could be totally random (or mixed up at least) for more of a sample-and-hold style of sound?

Anyone know who could build this kind of expression pedal for me if it doesn't already exist?

[fu22ba55]

Bump.

Can anyone point me to someone who could build something like this?

[ehque]

Uh this doesn't make sense... The expression pedal won't even be in the signal chain, so how can it impart a "sound" to your sound?

I can't think of anything pre-existing to recommend to you, but it does seem like a possible build either electronically or with diodes/relays...

The simplest thing would be 2 normally closed switches next to each other, with a resistor of different value across each one. Stepping on them randomly will add either A, B, or A+B ohms into the circuit, which will give you 4 "steps". I would choose one resistor to be approximately 1/3 the sensitivity of your pedal, and the other one to be approximately 2/3.

[bigblondeafro87]

I think it would have to be midi, because I've seen VSTi's where there is a knob to make the filter sweep more stepped and less smooth. Its called the arcdev mainliner, its very nice.

[Taylor Livingston]

If the expression pedal is being used to divide a control voltage, then you could use a true bit crusher, not a sampler rate reducer, to do this. Selecting the bit depth would allow you to change the granularity of the response.

No pre-existing bit crusher pedal will work though, because nearly all pedals are designed to remove DC at their input, which would remove the control voltage.

Even with those stipulations, this would not work in cases where the expression pedal is used to divide an audio signal (volume, fuzz drive controls) or where the exp. pedal acts as just a variable resistance (many digital effects). In those cases, I can't think of a way to do it outside of a powered expression pedal, sending a voltage to a microcontroller which then selects fixed resistors based on the control voltage.

[jrmy]

I believe that the Copilot Broadcast might do the sort of thing you're looking for - quoting from the Copilot forum on www.ilovefuzz.com:

"the broadcast is a device to control the exp jacks on copilot pedals, there are 2 options each one with an out jack (the user will need to plug a cable): a-triangle/square wave (rate and amount) and b-sample and hold wave (rate and amount). there will be 2 jacks on the side so you can use a&b independently. I was trying to record the videos on the weekend but the plans didnt worked as expected... I tried with a moog pedals but i think it will be better to use cv (5v), i want to try with other pedals with exp jacks. Probably i will release a CV version for those with CV pedals."

There have been teaser videos, but apparently the pedal isn't in full production yet. Adam from Copilot did say that he was thinking of doing a production run for October.

[Feral Feline]

Originally Posted by fu22ba55

... Instead of it being a smooth linear change, could it be stair-stepped so it would abruptly change values ...

Changing an expression pedal from smooth linear changes to stepped seems simple to me if it's anything like a wah.

I've never had an expression pedal so my idea may not work with one, but it would definitely work on a wah pedal.

Most knob/potentiometers on pedals, amps, rack FX, electronics etc have a smooth linear rotation, as you noted. However, there are knob/potentiometers that have detents for selecting a distinct function (ex whereas a synth's volume knob will be linear, its wave selection knob will have detents for wave form: sine, sawtooth, square, rising triangular, falling triangular etc).

All a wah treadle does is "turn" a potentiometer for you. Replace the smooth linear pot with a pot that has, say, between 5-8 detents and your treadle will "click" or "jump" between specific set values instead of sweeping through the entire range of values. You could then rock the treadle back and forth to different notches for a random-sounding set of values.

For ex., heel down is 1 and toe down is 8, then click the pedal back and forth to random intervals:
1
5
2
4
7
3
1
6
8
2

So, I'm sure this idea works with a wah pedal, but how about an expression pedal... can anyone tell me?

[NateS]

or, with an optical expression pot, you can redo the black partition thingy that the foot treadle is attached to, from a smoove V to a boxy opening.

very scientific wording, with thingies and boxies....

[Travis Harms]

The Moog MP-201 can output sample and hold to give you stair-step voltages. I'm not sure if it works with the expression pedal in the exact way that you are looking for but it might be the closest option. It is expensive, but it is a pretty powerful expression pedal.

[DerHoggz]

Originally Posted by Feral Feline

Changing an expression pedal from smooth linear changes to stepped seems simple to me if it's anything like a wah.

I've never had an expression pedal so my idea may not work with one, but it would definitely work on a wah pedal.

Most knob/potentiometers on pedals, amps, rack FX, electronics etc have a smooth linear rotation, as you noted. However, there are knob/potentiometers that have detents for selecting a distinct function (ex whereas a synth's volume knob will be linear, its wave selection knob will have detents for wave form: sine, sawtooth, square, rising triangular, falling triangular etc).

All a wah treadle does is "turn" a potentiometer for you. Replace the smooth linear pot with a pot that has, say, between 5-8 detents and your treadle will "click" or "jump" between specific set values instead of sweeping through the entire range of values. You could then rock the treadle back and forth to different notches for a random-sounding set of values.

For ex., heel down is 1 and toe down is 8, then click the pedal back and forth to random intervals:
1
5
2
4
7
3
1
6
8
2

So, I'm sure this idea works with a wah pedal, but how about an expression pedal... can anyone tell me?

No, those with that many "detents" are switches, not resistive loads/potentiometers.

[fu22ba55]

This is great and interesting stuff. Exactly what I'm looking for. I'll need to research the above suggestions, but I think we're getting close to the mark.

No lie, that Moog pedal is steep at $500.

Best bet would be for me to determine what type of voltage the pedals I'm interested in controlling want to accept and go from there.

[Taylor Livingston]

Originally Posted by DerHoggz

No, those with that many "detents" are switches, not resistive loads/potentiometers.

Not so, there are many true potentiometers with up to 40 detents. I've got one right here.

However, that wouldn't really achieve what the OP wants anyway, because even though they click at each detent, they do sweep continuously through the full resistance range. I guess it would sound more stair-steppy than a regular pot, but still somewhat continuous. And the granularity would not be selectable, so you'd be stuck with the number of detents that your pot has.

[Feral Feline]

Originally Posted by bassk81976

or, with an optical expression pot, you can redo the black partition thingy that the foot treadle is attached to, from a smoove V to a boxy opening.

very scientific wording, with thingies and boxies....

Made sense to me.

Originally Posted by DerHoggz

No, those with that many "detents" are switches, not resistive loads/potentiometers.

Bummer.

Originally Posted by Taylor Livingston

Not so, there are many true potentiometers with up to 40 detents. I've got one right here.

However, that wouldn't really achieve what the OP wants anyway, because even though they click at each detent, they do sweep continuously through the full resistance range. I guess it would sound more stair-steppy than a regular pot, but still somewhat continuous. And the granularity would not be selectable, so you'd be stuck with the number of detents that your pot has.

40! Cool...Thought so, cause I've had stereos with ratchety (rat shi**y) pots for all the controls: vol/bass/mid/hi. So my idea will work, to some extent. However, I've no clue what "granularity" is. I'm out of my depth here.

[DerHoggz]

Are those multi detent pots used by audiopiles? I remember seeing some audiophile tube head build where the volume control was a gigantic cluster of resistor looking things. Same thing?


Did those stereo controls ever stop, or could you just keep spinning them? If they keep spinning they are just telling the stereo, "Hey I'm turning!" which is adjusting stuff through a microcontroller.

Granularity is in reference to the size of the "jumps".

[Taylor Livingston]

Originally Posted by DerHoggz

Are those multi detent pots used by audiopiles? I remember seeing some audiophile tube head build where the volume control was a gigantic cluster of resistor looking things. Same thing?

The thing you're thinking of is called a "stepped attenuator". The idea is that even good pots have fairly bad tolerance, so in a stereo, where you use a dual-gang pot to control the volumes of both left and right channels, the 2 resistance bands of the dual pot will not always be equal throughout the sweep, which means that, at various volume levels, the channels will not be in perfect volume balance. For audiophiles for whom that's a big deal, they make or buy these stepped attenuators, which are just huge rotary switches with resistors soldered across them. It's easy to get 1% or even .5% tolerance in fixed resistors, so the tracking between the 2 channels stays much closer than with a dual pot.

Mechanically, it's just a big switch selecting between resistors.

The multi-detent pots are just like any other pot, but with physical dents in the metal surrounding the resistive strip where a little finger clicks in. They act just like a regular pot electrically, it just feels different to the user. It's still possible to set them between the detents.

Granularity is in reference to the size of the "jumps".

Right, and that's just my made-up term since I'm not aware of a proper term for that concept.

[Skrogh]

If you have just a little experience with micro-controllers it shouldn't be to hard making something with a digital-potmeter.
Makezine had an article about a Muff controlled by an LFO vha. a digital-potmeter, this could easily be modded to fit your needs.
Linkey