Shruthi-1 Polivoks/4PM Sourcing


I’m in the process of sourcing the parts for two control boards, a 4PM filter board, and a Polivoks board, but have a few questions on substituting some of the IC’s. Trying to do most of my order from Digikey, but can branch out if necessary.

For the TL072, I found a TL072ACN (Digikey #: 497-7658-5-ND)

For the TL074, I found a TL074ACN (Digikey #: 497-7660-5-ND)

For the LM13700, I found what appears to be the same part (Digikey #: LM13700N/NOPB-ND)

For the LM4250CN, I found what appears to be the same part (Digikey #: LM4250CN/NOPB-ND)

For the 6N137, Digikey recommends 6N137MFS-ND

Any input on these choices would be appreciated, especially what to look for when judging the viability of replacements.


Looks good.

when in doubt, read the data sheet. The suffix usually relates to packaging or other non-important stuff

Awesome, thanks guys.

Sometimes I’ve seen the suffix change details like the pinout or the gain bandwidth for an op amp. The details may be minor, but I’m not 100% on what’s important when sourcing audio parts.

Well, the pinout is quite important :wink:

Of course, lol. I meant that I agree that most times the details that change are minor, but that the devil’s in the details sometimes.

This LM4250CN component now seems to be discontinued can anyone point me in the direction of an equivalent, Ideally from mouser.

There is no equivalent. It’s a very odd part – a rare function (programmable op-amp), with just the right specs to be used as a filter for audio range frequencies.

You can still find the chip on ebay or from brokers!

I didn’t want to take the chance of buying fakes on Ebay and brokers are just as much a gamble.
Thank you for a prompt reply, I guess I’ll have to see what I can come up with. Any finding I’ll add here for anyone else looking to build it.

An alternative might be to go with the original Polivoks chips and some modifications of resistor values as mentioned in (not sure about what does values should be though).

Ericasynth sells k140ud12 (corresponding to UA776).


I just noticed that the 4250 is still available at some small scale suppliers, e.g. electrokit in Sweden:


… it’s also available from Banzai music: , so basically you should be able to source one from somewhere…


Thank you for spending time to find all these places. I’ll give them a go.

I have another question…
I’ve just finished building the SMR4 board but it causes the main board to crash/hang after a few seconds.
I’ve tried it on another Shruthi and there’s no issue with the CS or SVF boards I have, any ideas?

No idea, but it’s probably power-supply related… That’s the only thing I can think of that would influence the behavior of the digital board.