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Pedal to eurorack spring reverb diy
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Pedal to eurorack spring reverb diy
I have gotten hold of a spring tank from accutronics, the 8AB2A1B. I wanted to try it out in a eurorack environment. I also was given a fresh pcb with the circuitry from the Stompbox cookbook. So basically its a guitar pedal. Here it is

The tank and circuit is tested, so they work together. My concern is that this circuit wouldn't be able to handle a eurorack type signal.

My level of diy is still just copy/paste the electronics. Can anyone help point out how to convert this circuit to better fit in a eurorack? Hopefully by just swapping out some components.

I would just try it.
And if it does not work as expected, there are always solutions:

Click 'Modules'; the Stompbox adapters are on the end of the (long) list

Great things there btw....
This is a nice one to learn to tweak a circuit.
First check out the 33172: This is a single supply OpAmp with a low power consumption. Very important if you want to run it from battery. But you don't. You can use your OpAmp of choice, because you will have +/- 12V.
The LM386 is a 0.5W amp (typically for headphones) to drive the springs. You don't want to change this.

Then you have to think about the input/output levels: A guitar has just some mV, your synth +5/-5V signal level. The input stage has to amplify the weak guitar signal, but it will distort your synth signal. Look at the feedback transistors and you will see. Same for the output stage. It is reducing the level to the expected level for a guitar. You don't want that.

It is very easy to calculate the OpAmp feedback resistors. As a starter check out e.g. EEVBlog's OpAmp tutorial at YT.

Summing up: Use a different OpAmp instead of the 33172 (e.g. TL072), tweak the feedback circuits and last not least modify the power.
Yes! This is what i needed. Although i would much appreciate if someone could point out in that circuit which resistors to change on the input and output feedback. I have built some basic sallen-key lp filters before which i believe have some kind of combination of resistors for gain in the feedback and directly to ground, can't really find anything similar to that here.
Anyway, I'll go through the tutorial and see if i can spot them after. Otherwise those cgs circuits looks very useful, great library. thanks!
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