Waveform 0/1 and not -1/1

Hi, I’ve passed audio of shruthi-1 in an oscilloscope and seems that signal is not from -1/1 but 0/1! someone can explain me?

I think you are speaking for the OSC signal from the Digital Board?

If so think yourselves: how could a +5 V powered Circuit emit negative voltages?

If I plug a guitar into my soundcard and then recor audio, I see the signal that go from -1 to 1 (min to max of the range), but if I plug shruthi I see only from 0 to 1 (middle to max of the range)

What waveforms or presets did you use?

I have scrolled from all the osc shape, and reported the same result

Are you talking about the output of the Shruthi or the OSC> pin?



Maybe you have a problem with the 5V rail, or maybe an op-amp with a bad soldering joint on the V terminal…

While we are at it: on which point the offset Voltage is added to the OSC signal? Im staring at the schematics but obviously im do dumb to see…

Does C21, the 4,7µF Bipolar Elko do the trick?

Yes, this is not an offset, just high-pass filtering with a ridiculously low cutoff.

This is the difference from shruthi and virus saw waveform recorded on the same input of my soundcard. both are init patch, cut off at maximum, only osc1 saw shape! what is the problem?

The problem is the Virus doesnt produce a nice Saw :wink:

Noooooo, :frowning: , the shruthi is the first image! I must understand if this is ok, the standard work for shruthi or if I have done something wrong in soldering some piece!

No this is not normal, you have a problem with your build. Check at which point in the filter chain the problem starts to happen. Is the -5V rail OK?

I don’t know, can you send me an image of wath point on the board, and what test I have to do with multimeter? thanks very much!

Nix Multimeter, see here and here but you may use your soundcardoscillodings as well instead of listening.

The Virus doesnt have a nice Saw because on the negative edge its kinda smeared. I never measured but i think many other Synths can do better and produce a sharp Edge. And it doesnt look linear on the rising side.
Even i can do better.

from the troubleshooting section on the build page

OK, now my shruthi-1 is perfect, thank tou all very much!

Now you see how a Saw should look like. No pesky swing swangs like on the Virus - as if this would matter after Digital Filtering :wink: