Ambika SVF filter card issue, broken low pass?

On my Ambika I have 2 SVF cards. I’m quite fond of them, I haven’t been able to play around with them as much as I wanted, but I was testing them this evening and noticed an issue.

I will disassemble the Ambika later on and see if I can’t trace the issue with my multimeter, but from the way the filters sound, one of the SVF cards is lacking a proper low pass filter (it actually kind of sounds like the high pass filter is acting like a low pass filter).

Please listen to https://soundcloud.com/portervance/ambika-svf-filter-issue

The first 3 samples are SVF card #1, opening up the LP, BP, and HP filters then bringing them back down to 0. The second 3 samples are SVF card #2 (the one that has issues) doing the same order of filters. The last 2 samples are just a comparison of SVF #1 LP filter and SVF #2 LP filter. What’s going on here?

That’s one of the things I hate with SVFs (vs cascades for example) - if something breaks, the whole filter behaves differently and you can’t know where…

Check all the solder joints on the faulty voicecard. Check for styroflex capacitors inserted in the wrong set of holes. Check for leads of styroflex capacitors touching the board sitting on top of them.

Hmm, it must have been an issue with components touching each other in the stack of SVF cards. I swapped the top and bottom cards and also bent the styroflex caps a little more towards the board. Seemed to do the trick, both SVFs are working as intended now. Thanks for the quick response!