smr4 mkii filter tuning problem

I have just completed building a shruthi XT, but hit a snag when I went to tune the filter. Everything else seems to work as it should.

The self oscillating tone is very faint and there is also a background whitish noise (with the settings as stated in the instructions).

I did not install the 1M resistor and after scouring the forum before posting this, I now realize I should have. Will this likely correct my issue?

If not I can post a pic of my board.


> Will this likely correct my issue?


First thing to check: at the exception of the self-oscillation issue, does your filter still sound normal?

I believe the filter is working correctly as long as I’m not in the shape “none” on osc 1 and 2.

I just plugged it in again and the self oscillation was working. Clean pure loud sine tone. Almost had the filter tuned after a couple mins of fiddling, then the sound disappeared to what I explained in my first post. Sounds like a bad solder somewhere?

I have photos of my board to share if needed.


Which PSU do you use?

Olivier, thank you. I tried a different PSU and everything is working fine. Mark this one solved.

I now have an Anushri, Ambika and XT all built and working wonderfully. Will be starting Ambika #2 shortly!