How hard would it be to build an envelope follower?

Hi, I’ve been thinking of using the Shruthi-1’s filter to process my electric bass sound. With a Behringer FC-1010 foot pedal to control the filter cutoff/resonance, this sounds very nice. But ideally I would like something like an auto-wah. So this raises the question, how hard would it be to build an envelop follower? I’m thinking something that connects to one of the extra CV ins on the input expansion. I’ve searched the boards but haven’t found anyone who seems to have done this before. Would it be feasible at all?

It’s a very simple circuit (rectifier + low pass filter ; maybe two diodes and caps in the filter to have a fast attack and a slowww decay).

However, it would be silly to connect it to the input expansion port. Just sum it into the bit of circuitry scaling the cutoff CV. The entire thing will stay in the analog domain and you won’t have to care for sampling rate or voltage range issues.

True, but if you go into digital you can use it in the matrix… lag it, scale an LFO with it etc.

…… and you will have to live with a sloooowwwww update rate compared to audio signals.

True. But it’s an envelope, it may well be slower.

Slow envelopes suck. :slight_smile:

Yes, for example like in the Matrix 1000.

Here’s a simple schematic:

Hope it helps!

Martin