Open Theremin V3 Volume issue

Hi,
I have an Open Theremin V3 which I have recently set up with an old amp, using an old laptop as grounding through USB.

Up until today, it all worked perfectly, but now the volume antenna has a strange issue: it is not linear from zero volume - when I lift my left hand, there is silence until a certain point and then the tone cuts in.  From there it is a linear volume progression.

Any idea what could be causing this?

the only thing I have changed since yesterday is to tidy up and cable tie the cables of the amp and speakers, not the USB or audio cable from the theremin.

Hi,I have an Open Theremin V3 which I have recently set up with an old amp, using an old laptop as grounding through USB.Up until today, it all worked perfectly, but now the volume antenna has a strange issue: it is not linear from zero volume - when I lift my left hand, there is silence until a certain point and then the tone cuts in.  From there it is a linear volume progression.Any idea what could be causing this?the only thing I have changed since yesterday is to tidy up and cable tie the cables of the amp and speakers, not the USB or audio cable from the theremin.

It looks like the issue was that I had the theremin sitting on top of the amp.

I built a three-shelf stand, which I used to house the speakers at the bottom, laptop for power and grounding in the middle and the theremin sitting on the amp at the top.

I moved the amp so that it is now on the middle shelf, and that seems to have solved the problem.  The theremin has the top shelf to itself.

Don't know 100% if it was electrical or inductive interference from the amp, but if anyone else has similar issues while positioning their Open Theremin on top of an amp, might be worth moving the amp to see if that sorts it.