Reversing Envelope Detector

Thread Starter

QuinnF

Joined Jun 19, 2023
3
1687218140019.png
I've been trying to invert the output characteristics of this envelope detector design from outputting ~300uA over the 27k resistor at the bottom when the input amplitude is below ~1.2v amplitude and ~0A over it when the input amplitude is above ~1.2v. I'd like for the circuit to instead output ~300uA when the amplitude is high and ~0A when it is low. Is there any easy method for this preferably without adding new power rails?

Heres a link to my falstad sim if needed.
https://tinyurl.com/25j64wgo

Thanks for any help!
 

Thread Starter

QuinnF

Joined Jun 19, 2023
3
Im really just trying to experiment with a compressor effect pedal for guitar I have and turn it into more of an expander/noise gate. No strict requirements, just wanted to see what would happen.

Here's the full schematic, with the envelope detector section on the right
mxr-dyna-comp-schematic-parts.png
 

LowQCab

Joined Nov 6, 2012
4,078
Trying to produce a working Circuit based on the Schematic of a Pedal that was
specifically designed to be as Cheap as humanly possible, and
using Transistors that may no longer be available, is likely to give unpredictable results, at best.

Are You interested in how to accomplish this with modern Op-Amps ?
.
.
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Thread Starter

QuinnF

Joined Jun 19, 2023
3
I was able to successfully simulate it with a simple inverting buffer made from an opamp.

I'm mostly just curious about accomplishing it with transistors if possible. It is using common 2n3904s that I have no shortage of fortunately.

I'll probably just make a little opamp daughter board if it's not doable through some simple adjustments/replacements/additions.
 
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