LFO Expression Pedal

[slammer88]

Hi everyone.

I want to make a simple layout that will act exactly like expression ramper; an automated expression pedal so to say.

I want to use this with any pedal that accepts expression pedal to tinker around with its settings externally & automatically.

Expression ramper seems based on Atmega and digipot, but this can be achieved in a more simple way by using a basic LFO circuit. First of all, I'd need a basic full on / full off -you can call pulse- type of expression, with a rate pot indeed.

Has anyone made something like this before?

Before I forget, I'll feed this circuit with 9V, along with other pedals, and the output voltages to EXP should be between 0 to 5V (or 0 to 3.3v, I need to measure the pedals input)

 

[swyse]

Have you seen these before? I think the left brain does sort of what you're talking about here, albeit with a ton of options.

 

[Robert]

Ramping a control voltage is simple, but ....

I want to use this with any pedal that accepts expression pedal

Quite a few pedals are expecting a variable resistance, not voltage.

You could still accomplish it with optos/LDRs, but a digital pot would be more precise/predictable.

 

[Robert]

Have you seen these before? I think the left brain does sort of what you're talking about here, albeit with a ton of options.

Those look really cool, but my goodness, $329? I'm in the wrong line of work.

They do look really cool though, functionally and cosmetically.

 

[slammer88]

Well, my current project is based on Behringer's DW400 (Boss AW-3 clone) and to automate its Humanizer effect. Normally, it can be used with Behringer's FCV100 exp. pedal OR by pick/envelope attack.

On which side this pedal would be then?

 

[Robert]

It's digital so it's most likely looking for a control voltage but the schematic I found is too blurry to see exactly how the EXP jack is wired up.

 

[slammer88]

It's digital so it's most likely looking for a control voltage but the schematic I found is too blurry to see exactly how the EXP jack is wired up.

Maybe this would help? Schematics of AW-3..

https://www.electronica-pt.com/esquema/func-download/85789/chk,10b4361f6ec6a181aaba2ad7ad7475c4/no_html,1/

And here the FCV100's schematics

Behringer FCV100 Volume/Expression Pedal (fixed schematic error) - Service Manual Free Download

Download Behringer FCV100 Volume/Expression Pedal (fixed schematic error) ✅ Car audio systems and stereo equipment, amplifiers, speakers, subwoofers, cd changer, mp3 player - Pioneer, Alpine, Sony, Kenwood, Clarion, JVC - service manuals and repair guides

www.eserviceinfo.com

 

[slammer88]

Okay, so I got the pedal and gave it a try.

1- 50k pot seems to work fine, getting 0 to 2.7v from bottom to top,

2- 100k pot seems to work better(better peak points), getting 0 to 3v from bottom to top,

3- 220k doesn't work, but getting around 3.4v from top to bottom, I think it exceeds the limit somehow.

4- I used 3 crocodile cables with a TRS Jack, removing any of them disconnects the expression function without physically removing the Jack, so that is good for using the bypass function with a switch.

Expression input is provided 3.3v from the pedal, (I knew that), but I've realized just now that I just can't feed it with some extra voltage, as it's already there. The circuit I'd connect should not provide any extra voltage, right? Or am I too sick to think correctly? (got sinusitis)

 

[jwin615]

On your trs expression jack you have a ground, send and return.
You'll have to figure out which is which.
You can do one of two things
Alter it in the analog domain with a pot or series of resistors on switches, optocoupler, etc.
Write code/Arduino/atmega/whatever to automate a 0-3.3v output to do whatever you want it to do(little unsure what your end goal is here but you mentioned lfo). Depending on what you use and it's current draw and voltage requirements, you *may* be able to use the 3.3v as it's power source, but then the two devices wouldn't be isolated and you also risk stressing the buck converter in the pedal and toasting it.
It may be a wise decesion to still modify the source(from exp jack) voltage via an optocoupler, vca, etc even with a digital 3.3v out.
That way the two devices are electrically isolated. That would prevent any accidental over voltage from reaching the pedal.
Also, on another note.
Strep is presenting itself like a sinus infection this year for many. Whole family has it. If you have lingering sinus issues, may want to get tested.
Hope this helps. Just woke up so tried to make this as coherent as possible.

 

[jwin615]

Those look really cool, but my goodness, $329? I'm in the wrong line of work.

They do look really cool though, functionally and cosmetically.

$330 for a couple of 555 flasher circuits, LEDs and some LDRs

 

[slammer88]

On your trs expression jack you have a ground, send and return.
You'll have to figure out which is which.
You can do one of two things
Alter it in the analog domain with a pot or series of resistors on switches, optocoupler, etc.
Write code/Arduino/atmega/whatever to automate a 0-3.3v output to do whatever you want it to do(little unsure what your end goal is here but you mentioned lfo). Depending on what you use and it's current draw and voltage requirements, you *may* be able to use the 3.3v as it's power source, but then the two devices wouldn't be isolated and you also risk stressing the buck converter in the pedal and toasting it.
It may be a wise decesion to still modify the source(from exp jack) voltage via an optocoupler, vca, etc even with a digital 3.3v out.
That way the two devices are electrically isolated. That would prevent any accidental over voltage from reaching the pedal.
Also, on another note.
Strep is presenting itself like a sinus infection this year for many. Whole family has it. If you have lingering sinus issues, may want to get tested.
Hope this helps. Just woke up so tried to make this as coherent as possible.

My goal is simply to introduce automation to my Behringer DW400 pedal's Humanizer effect. It's envelope controlled, but I thought I could make it automatized by tricking the expression input, faking a pot movement automatically.

Expression Ramper does the job but it's expensive for me, and I believe its also based on Atmega or something digital.

 

[giovanni]

Do you want to stay away from digital stuff? Because I feel like this would be easy to achieve with a microcontroller and a few analog components. The folks over at Adafruit may have what you need. This is the kind of stuff I would love to spend time on…

 

[slammer88]

Do you want to stay away from digital stuff? Because I feel like this would be easy to achieve with a microcontroller and a few analog components. The folks over at Adafruit may have what you need. This is the kind of stuff I would love to spend time on…

I don't mind that, I just look for a solution to make this done. I can use a small Arduino like Micro or something for this job. Some varieties would be better though, like variable duty cycle, or shape types etc. This can only be achieved with digital I guess?

 

[Feral Feline]

My goal is simply to introduce automation to my Behringer DW400 pedal's Humanizer effect. It's envelope controlled, but I thought I could make it automatized by tricking the expression input, faking a pot movement automatically.

Expression Ramper does the job but it's expensive for me, and I believe its also based on Atmega or something digital.

Is the following anything like what you're trying to accomplish?

SIDE STEP™ - universal variable state lfo

IN STOCK. Please allow up to 10 business days for us to build and test your Side Step.Once your Side Step ships, you'll receive your tracking information. The Side Step™ is a variable-state, tap-tempo low-frequency oscillator (LFO) that can be used to control practically any device with an...

godlyke.com

 

[slammer88]

Is the following anything like what you're trying to accomplish?

SIDE STEP™ - universal variable state lfo

IN STOCK. Please allow up to 10 business days for us to build and test your Side Step.Once your Side Step ships, you'll receive your tracking information. The Side Step™ is a variable-state, tap-tempo low-frequency oscillator (LFO) that can be used to control practically any device with an...

godlyke.com

Thats a big affirmative, sir!

 

[Feral Feline]

If only there was someone who knew how to trace things.
If only there was a forum member who had one of those yellow Side Step pedals...

 

[slammer88]

If only there was someone who knew how to trace things.
If only there was a forum member who had one of those yellow Side Step pedals...

View attachment 60134

Should i take this as an irony or not?

 

[Diynot]

If only there was someone who knew how to trace things.
If only there was a forum member who had one of those yellow Side Step pedals...

View attachment 60134

Would the MBP Tappy or Wavelord do the trick? Also “turning knobs like an asshole” might be a great tagline.

 

[Diynot]

Def checkout the Madbean pedals Tappy project, it can output VCO, resistive, and optical control

 

[Feral Feline]

Should i take this as an irony or not?

I actually came up with the LFO-controlled expression concept on my own, born of need — I wasn't aware of anything that could do that.
However, I wasn't quite far enough along the DIY path to make my idea a reality at that point in time.
Later when I saw my idea "STOLEN", ie implemented, by TWA...

I had mixed emotions: I thought I could bring a unique product to market, possibly, but wasn't sure of my theories; and then that feeling of vindication that my idea had not only merit but could work in the physical world — though beaten to the punch, I had to have one.


I've got all the MBP Tapanator-related PCBs, too: controller, phaser, trem, wah, Wavelord, DigDug2.



If there were enough interest, somebody could send a known tracing-expert one of those units to be traced, maybe have a few PCBs made.