Testing frequency changes related to pulse width

Update: Solved - it is not pulse width that is the issue, it's the pulse amp CV, just as in the waveshaper

 
The AS3340 suffers from a problem with the pulse width circuit where the oscillator frequency changes when the pulse with changes. 

I have made a separate circuit to prevent this, and tonight I did some measurements on the VCO to see if the fix worked.

Surprisingly, it did NOT:

 

The frequency is clearly directly related to pulse width. I don't know why, but it definitely means I have to look into this. Again. At least, this time I have a good tool for measuring stuff.

 

For reference, without modulating the pulse width, the frequency is stable:

Update - found the reason

For simplicity, I had connected the pulse width CV and the pulse amp CV together, even if the pulse amp is not in use.

When grounding the pulse amp, the frequency became stable:

 And then, with a stable pulse width (CV at 2.5V) and a changing pulse amp CV, frequency changes

 

Testing with updated VCA

With the new component values, the frequency is stable:

 

Pulse wave amplitude is changed a lot without showing up on frequency

Linear FM

And while we're at it, I checked linear FM (and routing of exponential FM), it works as expected:

Yellow: Output of DCO B, blue: output of VCO. DCO modulates VCO pitch

 

 

Red is VCO frequency, it clearly follows the DCO above. Note also that it is capped at 0, a through-zero FM VCO would work better here. That's for the next version of the VCO.

All in all, I'm pretty confident the new VCO version works as it should.