OTA wah

[Nasse]

Found this link when Googling SSM2040. It is originally seen in very old Elektor "Wah wah pedal" circuit snippet. Needs some parts more to be practical guitar effect, but interesting anyhow, read my lips no inductors

http://www.uta.fi/~helin/sch/3polevcf.jpg

[smoguzbenjamin]

A twin T wah is also inductorless and also a lot simpler

[Nasse]

Yeah sure but this has adjustable Q and is voltage controlled, just plug in the envelope gen or LFO, and OTAs are claimed to sound good when cranked.

Maybe few parts could saved if made with two LM13700s, you have one OTA too much but a wah/vol pedal could be made

[R.G.]

A single LM13700 plus a couple of opamps makes a state variable filter along the lines of the Mutron. You control the filter frequency with a single pot changing the current into a two-output current mirror.

This is one of the redesign blocks I'm working with on the Ludwig phase 2 reverse.