JRC/NJM 2121

[RobA]

I've been looking for some ways to do audio routing and presets from a microcontroller and I came across this slick op amp, the NJM2121D. It's essentially a slightly beefed up 4558 with two input sets and a single switched output. I think it would be pretty slick for use in various effects, but I can't remember seeing it used anywhere. Does anyone know of an effect that uses one of these?

Here's the link to the spec sheet,
http://semicon.njr.co.jp/eng/PDF/NJM2121_E.pdf

[stecykmi]

i've never seen this device before, but it is pretty cool.

[RobA]

I bought a couple of them from Mouser to test. I had a chance to do some playing with them today. They do sound good. I built a couple of distortion circuits with multiple gain structures that could be switched with the switch input. It works really well. I think there's lots of potential here for things like channel switching and having multiple filter types. But, I think there's room for more creative stuff too. I've only been switching it with a toggle so far, but the switching seems fast enough and quiet enough that it should enable some things like stutter distortion.

[stecykmi]

ya this is such a unique device, we'd have to invent some cool uses for it.

how about a envelope driven stutter? the envelope could control the ratio between the on/off time.

or an asymmetric distortion? hook up the audio signal to a comparator. the comparator drives the switch, such that the positive side of the signal gets a different gain/filter structure than the negative side.

an octave effect might also be possible using flip-flops like the lowrider.

[RobA]

Every one of those is an interesting idea. I've got a couple of ideas I want to try out before I talk about them. One of them is related to the envelope driven stutter.

I hadn't thought of the octave effect at all. I wonder if it is fast enough at switching to do it.

I've placed a couple of parts orders today to get some things I need to experiment with. Hopefully I'll get to do some breadboarding by this weekend.