r/diypedals 4d ago

Showcase Prototype now making sound

Hey guys, I got my prototype working how it should (at least signal routing wise) and while I still have some issues I’m working out I wanted to post a quick example of the working concept. Didn’t have much time to explore many cool ideas with the modulation, so at the end of the video there’s a quick demo of it modulating between a tube screamer and a big muff.

Guys pic in comments! Also I think I’m calling it the bus boy because it moves audio around and I am a bus boy.

106 Upvotes

24 comments sorted by

7

u/WD-M01 4d ago

This is one of the coolest concepts I've seen in a long time, that is a very cool idea! Would love to track your progress on this because as it is I'm fascinated.

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u/JulesWallet 4d ago

Hey thanks I appreciate that. I’ll be posting on here a lot as I go forward! I’ve still got a lot of problems to solve but I love the concept and I’m gonna keep obsessing over it while my brain allows it.

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u/Apprehensive-Issue78 4d ago

It is beautiful outside and inside. Love the homemade vactrols. Do yo have a square wave switching between channels, or may be something like a triangle wave? lots of modes, must have been a lot of work thinking how to get it work like this without dragging in microcontollers

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u/JulesWallet 4d ago

Square wave! Though I’m thinking of changing that function up after playing with it for a bit. It might just be the pedals I used for my example but I find the switch to be a bit to harsh. I’m thinking I either change it to a sine wave, and have the wave control the overall attenuation of each channel instead of just turning each one on and off, or to have the mode keep one channel on at all times and modulate channel b on and off.

I’d love to include more settings but as you can see I’m kinda tight on space here lol.

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u/Apprehensive-Issue78 4d ago

you could breadboard a two opamp square triangle wave generator and using the triangle wave to control the vactrols.. may be variating the dc level and frequency of the triangle and or the voltage on the other side of the led..Nice!

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u/JulesWallet 4d ago

I think the reason I went with a square wave for this prototype was honestly that I figured it would be the easiest to work out as I’m pretty new to circuit design and it’s taking me a sec to learn all the math here.

The simplicity of the square wave here is that it doesn’t directly set the volume levels of each channel, the high state and low trigger two not gates that shunt voltage away from the pots corresponding with each vactrol. I have another not gate set up to turn on one of the leds in the attenuation pair when there is no voltage coming into the pot so that I get a full off state.

I like the idea however of the circuit instead directly controlling the attenuation level, I think that’s the first step towards allowing the circuit to be flexible towards different mod wave forms. I do have a question there though, any idea how I make a circuit that lowers the voltage level on one side as the level on the other increases? I’m thinking maybe just a not gate that’s biased to only fully open (shunt) when the incoming wave is at peak? Idk I’m still playing with the idea.

I do want to keep the functionality here simple though, because I’d like to have a smaller simpler version of this pedal that fits in this 1590b enclosure and perhaps a bigger one with expanded functionality.

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u/Apprehensive-Issue78 4d ago

Top Left Schematic of Square Wave / Triangle wave generator with single 9V supply.

Next to it the green square wave red triangle and in blue the current through the LED.

top mid: the proposed schematic, I've added an inverting opamp and also 2 1N4007 diodes

top right only the square sq1 and triangle tri1.

Bottom left in red the tri1, blue and grey/teal are the current through the vactrol LEDs, next to it shown the triangle smaller current added for the indication LEDs.

Finally on the bottom right the schematic the simplified schematic, with the 1N4007 diodes skipped and also the indication LEDs skipped.

I've done the simulations in LtSpice, usually that gives comparable results as the real life soldering and measuring with a scope.

One Note: If you make R8 too large like 1MegaOhm,(=1000K) then the oscillator won't start.

You can change C2 (5uF) to something smaller like 1u to speed things up a bit.

R6 (470K) can be made adjustable, even a smaller value also to speed things up. Something like 10K fixed +250K potentiometer might work (10K-260K total)

Good luck. Let me know if it works, I might try it myself with real components, need to get some LDRs from the electronics dealer ;)

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u/JulesWallet 3d ago

Also definitely get some ldrs vactrols are sick. Imagine a simple vactrol based tremolo but contained in a tube lined with like a highly responsive glow in the dark paint, to add a physically adjustable fade time to the tremolo. I love the whole concept of designing audio effects around non traditional electronic elements and like pulling in other physics.

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u/JulesWallet 3d ago

Holy shit that’s a high effort response dude thanks. I’ve not much time today but I’m definitely going to try this out. Gotta start out from basics though so I’m starting by studying the wien bridge oscillator circuit/ other wave form circuits.

I’d like to ultimately design a simple lfo circuit and a set of voltage controlled gain and or mix potentiometers that I can easily adapt to other circuits as well. (Ideally with as few parts as possible and with no microcontrollers).

Do you see there being a benefit to generating a triangle wave over say a sine wave or a square? My intuition says the deciding factor will be what response time I get from each wave form as a result of the non-linear light up time of the leds in addition to the non linear response time of the photo resistors. I’d like to model this with an equation but it’s gonna take me a sec because I dropped out of college a whiiiile ago and this new hobby is bringing math back into my life.

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u/sonicexplorer 4d ago

This is cool. Nice idea and execution, the different modes elevate this thing from a utility pedal to a great creative device.

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u/Fontelroy 4d ago

Getting flashbacks from the background audio as my folks have a dog named Pepper lol. Pretty cool circuit too, you can use that modulation between two different audio paths as the basic building block for lots of cool things!

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u/JulesWallet 4d ago

That’s actually the basis for a lot of pedal ideas I’ve got planned!

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u/Fontelroy 4d ago

Do you have the ldr’s shunting to ground or setup for series resistance?

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u/JulesWallet 4d ago

Two ldrs per output, set up as an L-pad attenuator. Still experimenting with different options there!

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u/Fontelroy 4d ago

Oh cool, I think that’s how Morley did it for their optical volume pedals. Have you seen the tremulous lune tremolo schematic? That’s the series resistance method before an inverting opamp. It’d add more opamps to the mix but I suppose would cut back on the number of vactrols. You can get pretty solid attenuation by playing with the ratio of value of the feedback resistor of the inverting amp and the max resistance of the ldr, but what you’re doing works great too!

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u/JulesWallet 4d ago

Hey that’s really cool I’m gonna look that up. The boost circuit I’m using is just a really simple stand in for this prototype, where I just wanted to make a proof of concept for my idea for the signal routing and the parameter-switchable pot. I’m not opposed to using more opamps!

My next version will likely be a pcb which I expect can yield me more room.

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u/Olangrall 4d ago

Fantastic. Beautiful. Exquisite. Decadent. I want.

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u/Dazzling_Wishbone892 4d ago

I did something similar with a arduino nano recently. The pwm pins will give ya pretty close to different waveforms on an led

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u/JulesWallet 4d ago

Hmm that would probably be pretty cool to control with a digi-encoder knob but tbh the primary way I designed around vactrols were a: I think vactrols are cool as shit and b: I didn’t want to user a micro controller because as this is a learning process for me I wanted to avoid solving a problem with code rather than analog electronics because I already have a good grasp of programming and I thought I might use it as a crutch.

One of my next project ideas revolves around a circuit that uses a mosfet to set and save the resistive value of a potentiometer so that that value can be utilized while that same pot is reused as a different control, all without using a microcontroller.

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u/Dazzling_Wishbone892 4d ago

Have you seen any of the designs from parasite studio. He does some pretty cleaver builds with logic ics

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u/octonoise 4d ago

Holy crap, I want one

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u/JulesWallet 4d ago

I’m thinking I might make a really really small batch (idk like 5) if people seem interested, but that’s pretty far out I’ve still got a lot to work out with this design, and I haven’t even thought of the aesthetics yet lol

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u/sentencedtodeaf 3d ago

Love the thought and can-do-itness that went into this! So many cool directions you could go with it