Intermittent electrical noise - SVF filter board

Hello, everyone!

I just bought a Shruthi-1 with the SVF filter from its original owner, and I’m worried they sold it to me because it broke. It creates a lot of electrical noise - not all the time, but intermittently. Sometimes it will just be a quick burst of noise, sometimes it lasts 5 minutes and totally drowns out any other sound coming from the device. It seems to happen most if I adjust the parameter of either oscillator, or if I tweak the second filter in any way, but other times it just starts without me tweaking anything. It is not similar to the noise generator, it’s a crackly, loud, gnarly noise. The filter setting on the utility screen is set to svf.

I don’t have any electrical tools of my own, so I don’t know what I can even do about this. But does anyone here know what the issue might be? I’m hoping it’s fixable.

Edit: nevermind

The first place to look will be the connectors between the PCBs, the output connector and the power connectors. I would reflow and/or redo these solder joints. These are the ones that get the most abuse.

After that you’ll have to look for other bad joints on the PCB before investigating if there’s any bad components. Also make sure socketed ICs don’t have legs folded under the IC body.

Thanks for the suggestions. I’ll open it up this evening and take a look. I’ve never dealt with electronics before, so if there are no obviously loose connections I’ll post some pics here and hopefully someone will be able to tell me what I’m looking at.

It might just be a borderline external power supply that just barely provides enough current - I have one plugged into my Shruthi offering variable voltage ‘taps’, and if I turn that voltage down to a lower setting the sound starts to occasionally break up, rather than fail altogether.

It might be worth trying a replacement before investigating further.


Have a read here for instance.

(Some minutes later, I finally tracked down a post I made way back in April 2012 detailing what happened with different PSU voltage settings and my own Shruthi SMR4-mkII here ).

Hope it helps!


Maybe a wrong 4052 . The normal 74HC4052 works with 5 Volt . Some special with +/- 8 Volt .
Bu have +/- 8 Volt power on the rails .Or use a CD 4052.
The other thing can be - a bad contact on the 6 pol headers
Check it .



Thanks for the suggestions, everybody. I haven’t actually been able to open the thing up because I don’t have a small enough allen wrench for some of the screws, but I’ll have to pick one up if a new power supply doesn’t help (thanks for that tip, yewtreemagic). FWIW I am using a 9V 400mA PSU right now. The only other 9V I have is 600mA. You mentioned in that thread that running the Shruthi with a higher ampage will cause some components to become a bit hotter than usual. Will that potentially cause damage?

> You mentioned in that thread that running the Shruthi with a higher ampage will cause some components to become a bit hotter than usual

That’s not correct. You might be confusing voltage (V) and current (mA).

A power supply only delivers as much current as the circuit need. So if the circuit requires 100mA, a PSU rated for 400mA and a PSU rated for 600mA will both deliver 100mA.

Overheating will occur only if you use a higher voltage (12V instead of 9V for example).