Shruthi-1 ssm2044 : Very Low Volume from Output

Hi Shruthi folks !
I’m a new happy builder of ssm2044 version, everything work nice except that the sound from output is very low ! i have checked the trimmer for gate but it doesn’t change something. I have turned the other one but same thing. Can you indicate me what’s measures i must find on ssm2044 or 2164, it seems that vca doesn’t work properly.
Thanks.

Do you have access to a scope?

Yes

Yoohoo! I’ll scope a few strategic points tonight and tell you the readings…

Thanks a lot Man :slight_smile: !

Hello.
I have built a kit with smr-4 filter today.
Everything looks fine but i have also very low sound.
I have to set my mixer input to max sensitivity and the shruti and i can barely notice that there is a sound.

I have been looking everywhere on the boards to see a short or a bad soldering but i do not see anything.

Sadly I dont have a scope.
But i have a multimeter.

Do you have any suggestions?

@jazzdoktorn: Read this: http://mutable-instruments.net/forum/comments.php?DiscussionID=563&page=1#Item_17 . Someone had the same problem and it was a missing “bridge” on one of the pads for the pots.

I was looking around the discussions here on the forum and i found exactly the same post that you were telling me about.
I was just coming back to try to remove my post here so i wouldnt have to feel stupid and blind.
Then i saw your post…

Thank you for a fast response.

@pichenettes

maybe change the “solder in” bridge to a “break circuit” bridge as the missing bridges seem to cause more problems than nonworking volume pots… :wink:

Any update ?

  • a: oscillator waveform with unfiltered HF content, ~3V pp
  • b: same as a, but attenuated, 10mV pp
  • c: nothing if the HP filter is set to 0. As the cutoff of the HP is increased, you should see the equivalent of a progressive low-pass filter sweep on the oscillators signal
  • d: VCA output, 200mV pp
  • e: final output, ~2V pp
  • f: filtered envelope CV. With the “init” patch: peaks at 2.5V, 1.5V on sustain, then 0V when key is released
  • g: filtered envelope converted to the SSM2164 log response: 3.6V (or whatever your op-amp clips at) when no key is pressed, down to 0 or 0.5V when a key is pressed

You cannot probe the output of the SSM2044 directly, it is a current! It is directly fed into the VCA (which has a current input).

Hi Pichenettes,
great, thanks a lot for your explanation. I will probe them next day, i’m just coming back from my studio and too tired to go back.
I have probe osc and vca connectors and heard normal sound in osc but strange sound in vca connector.
I will let you know asap.
Have a good night
K.

Oh yes another question, you can read TL084 into board but in BOM that’s TL074 which is indicated. Of course i have bought and put TL074 into board.Is it important ?

It’s not a big problem. I prefer TL084 for CV signals since they have slightly better DC performance (low offset), but it’s nitpicking.

Hi

I have the same problem : very low sound. I’ve build 2 Shuthi with SMR4, both of them work perfectly, but this analog filte refuse to work as it should, and can’t fix it ( double check components, solders … ) evrything seems ok, but with a very low sound.
here is my readings
a : 2v pp
b : 90 mv with a square waveform
c : constant 50 mv
d ( out of ssm2164) 200 mv pp
e: 50 mv pp
f : 1,72 v
g ; peak 3,92v ( key pressed : 720 mv)

and the resonace knob seems to work as a overall reverse volume knob : 0 : max ( low sound) 128 : almost no sound

Here is an example :

did I miss something ?

Ok, i have made some measures with my scope
a = 150 mV
b = 0
I have checked resistor value between a and b and it’s correct 47k
c = 0
d = 50 mV
e = 0,4 V
f = 0.2 V
g = 40 mV

Very low value ???

@ereyre: The problem seems to be located in the final amp stage, which has a 10x gain you’re missing.

@kroutshev: Your problem is different, it looks like a bad gain in the mixer section. Can you confirm that the voltage at the pin 1 of IC2 is 150mv pp? If this is the case, then there’s a bad resistor value or something wrong in the mixer section. Your picture is not clear enough for me to check the resistor values (and there’s a cap hiding them).

Ok pichenettes, i’ll check values tonigth.
Thanks

Values are correct but i use xOxbOx jack connector instead those which are indicated into bom. These jacks are stereo and not mono as musikding model … that’s why volume is so low i suppose …

@ Kroutshev

I am not sure you can use the x0x ones, they are normally closed and hacking them into the shruthi may be doing something that you dont expect. Check and make sure you are not shorting the tip to the sleeve