Shruthi SVF Clone Parameter/Sound Issues

Hello! I’ve got a clone of the Mutable Instruments Shruthi with a Dual SVF board that I can’t get to function properly. I’m fairly confident in my soldering and component choice, and reinstalled the firmware to version 1.03. Everything powers on as expected, but parameter selection isn’t reflected on the main display. I attempted to replace one of the multiplexers to address the issue (I erroneously used a 74hc165E where I needed to use the 165N), but without luck.

Additionally, sound output is a mess. I get a distorted, grinding buzz that changes depending on what parameter page is selected. (I don’t have video of this yet, but I can post it if needed.)

I can provide more photos of the boards if needed. I’m using a generic center positive 12V 5A AC/DC.

Have you selected “svf” as the filter in the system settings? If the wrong filter is selected the output will be distorted.

Thanks for the quick reply! Unfortunately, yes. I went through and made sure I had the right filter board and control board selected first.

My working theory right now is that either the voltage draw of the alternative LED’s or a busted Atmega644p may be the issue, but I don’t know enough to be certain

Here are some images of the boards:

I’m continuing to update this thread since this seems to be a recurring issue that’s difficult to resolve.

I removed the LED’s with the intention of using something much closer to the original specs, but the garbled sound continues. I don’t have another atmega chip, so I can’t test that yet.

Could this be an issue with the screen? I’m using one of these, and I’m worried the backlight may be the source of my woes.

I resolved the issue with some help from the Pusherman’s DIY Eurorack Noobs Facebook group. It turns out the issue was compiling the firmware using a version of gcc that was too new (I had 6.x something in my toolchain, but needed 4.3.3). It was suggested that this pointed Shruthi toward incorrect memory addresses, which would explaining the garbled noise and the nonsense printed on the page displays.

I ended up uploading a pre-compiled hex file from, sure enough, @Bjarne’s excellent YAM firmware, and now the UI is behaving as expected! (Of course, as these things go, I’m not getting any sound out at all, but I’m hoping this is a filter calibration issue).

Thank you!

TL;DR: If you must compile your own, try Emilie’s vagrant box. Otherwise, use a precompiled hex file. catch(err): make sure you aren’t using too new a version of gcc - it’s really easy to get the wrong version through Arduino’s package control.

I’m afraid this is very unlikely to be the cause of your problem – filter calibration only affects note tracking and cutoff matching between the two filters.

1 Like

I had the wrong filter type selected :man_facepalming:

Choosing the correct one was instant success! I have one more (non-MI) filter board to troubleshoot, but I’m now the elated owner of a singing Shruthi! Thank you for designing such an awesome little monosynth