What looks like an issue with the filter board (SMR4mk2)

Hello -

I’ve been building up a Shruthi-1 kit (v0.8 PCB, SMR4mk2 filter). I’ve been documenting my progress here - http://www.flickr.com/photos/infovore/sets/72157633835378992 .

It’s all together, which means I could start to tune the filter. However, that’s not proving possible.

When I turn off both VCOs and set the filter so it ought to self oscillate, I hear absolutely nothing from the output - well, not quite; just a faint hissing.

Also, when I try scrolling through the presets, it’s as if the filter board isn’t quite working: cutoff and resonance controls do effectively nothing (and as such, all the sounds are pretty similar - a bit buzzy, not quite like the demos of said presets).

I don’t have an audio lead or hi-res camera with me today, so can’t post audio demos or photos, but can do so on Monday. In the meantime: any idea what might be up, and where I ought to start looking?

Forget the tuning for the moment (the filter does work well without it)… Can you confirm that nothing at all happens when you modify cutoff and resonance? Have you plugged the audio cable in the right jack output?

(also: everything feels as if the envelope release is “dragging” a bit, but I think that might be related to the filter issue, so I’m going to solve the self-oscillation problem before I try anything else).

Audio jack is going into the right-hand jack socket, marked out on the board.

And yep, nothing happening there - some crackling, as if something is shorting out.

Is the VCA working?

Hunh, no - the two envelopes are having no effect on anything.


Entirely my fault: I’d absent-mindedly missed out soldering a few pins from IC2 on the filter board. Finished them up, all go - envelopes and filter working.

I did that the other day when building this filter. Its easy to miss.