AS2164 VCA odd output

[nigeld]

Thanks to some help here before I got a VCA model based on the @HAGIWO dual VCA, sort of working. What I have on the breadboard is here:

I’ve annotated this with what I think the parts are doing!

When I look at the output in @HAGIWO’s video I see something like the following:

Now that I’ve got past some of the problems I was seeing with the trimpots I get the following output:

Sorry if this is not very clear I just have a small handheld oscilloscope that I have to take pics of with my phone! It looks like I never get any positive output of the incoming signal and I get nothing if the CV goes below 0.

The questions I have are, do I need to apply an offset to ensure my CV is always above 0V? Also, why am I only seeing half of the output? I’m expecting to see a ‘diamond’ pattern based on @HAGIWO’s example.

BTW If you’re curious about the inspiration for this it can be seen on YouTube here.

[nigeld]

As an update I got a suggestion of adding in a cap and resistor to remove DC offsets on the input, so I updated the design to test the results. Here’s what I added to the design (ringed in red):

This let me do some tests and I got the following results:

So the addition of the DC offset works really well for this, except for the sine wave? Can anyone explain what’s happening here, do I need to keep this as part of my design or is there a better solution out there?