Shruthi-1 no audio output

hey there.

First of all I have to say, that i am a noob with soldering and circuits. During the last two days I built a shruthi with smr mk2.
I prepared myself with some tutorials and used the very well and clearly written instructions on
everything seemed fine during building (means testing of voltages, lcd-display, i get 7.49V on the input and 4.98V if i check the motherboard supply) and i double and triple checked the parts on the pcb. however my shruthi doesnt output any sound at all.
i tried several things: sending midi from ot, using the shruthi-1 sequencer, pressing the 4th knob for 2s to start the test note: nothing. i checked the solderjoints on both pcbs and remade them, if they looked a bit weird. i also bridged the 3 pole adapter for pole selection in the hope, it didn’t make contact with the jumper.

i think the problem has to do with something like this?:

  • i didnt pay attention for the direction of the ic sockets while building the smr mk2 board, but the ics themselves are the right way round (if that could be a problem)
  • still bad solder joints
    -on the other hand, i dont know if midi is really working.

i dont really understand how to narrow down the search. or what could be the problem, also after reading the forum. i hope someone can help me


First things first, did you solder the wire bridge beside the audio in/out connectors?

"Test note

Press S1 for a long period of time to trigger a C4 test note. Press and hold again to stop the test note. Coupled with the sequencer or arpeggiator, this allows the Shruthi to be used as a stand-alone instrument, without an external MIDI keyboard."

So you pressed the wrong switch for a very short period of time for the test note.
Please try again, this time holding switch 1 from the left for something like 10 seconds, post results :slight_smile:
As for the ICs, while it is bad form that you didn’t orient the sockets the right way, it doesn’t do any harm, unless you put something in backwards because you followed the socket instead of the drawing, which could very well destroy the chip.

Did you check that you sent midi on the right channel? If you get sound from the test note, check the shruthi manual & whatever you use to send midi, to see what channel both are sending/expecting midi from.

If you don’t get any sounds from the test note(even after holding the knob for a looong time), post pictures of both sides of the board.

yes, i soldered the bridges next to the audio connectrors.

the testnote doesnt work. i pressed several times for more than 10 seconds.

well maybe its the ics. because first i built the filterboard. and there it didnt say anything about orientation, so i just put them in the way they were laying around. but that was after the power adapter part, so i didnt test it yet. then i built the controll board, where i realized “oops the ics are polarized”. so i went back to the filter board and switched them into the right directions, except for 2 of the TL074. there is this dot on the oposite side of where it is on the other ics, so that confused me. so when i made the first tests with filter and control board combined the two TL074 were connected backwards.
could this mean i would have to order a new filterboard kit?

i tried with midi channel set to 0. nothing happens too. im not even sure if midi works. because there is no note sign on the display when i send midi to the shruthi and midi out and through both dont seem to work if connect my microbrute after it.

i will post some pictures later

ok here are pictures of both boards, front and backside. i dont know, maybe it could also be a weak solder spot? but with the information i got from the internet i cant really tell. some of them have too much solder, but im pretty sure i eliminated all the cold spots and all the spots where the connection to the pcb wasnt good.

1. You have swapped the EEPROM and optocoupler on the control board. That’s why you have no MIDI.

Try swapping them and check that you’ve got MIDI.

From there, if you still have no sound, please trace the signal on the filter board as explained at the end of the filter board assembly instructions.

ah now i see…i give it a try. thank you very much. need to improve my concentration.

ok it works now. thanks a lot for your help. i was worried the problem was much more complicated.