Just finished this one up tonight. Crazy as I remember, need to play around to see what all it can do. What is the trimmer for? Kind of sounds like it increases and decreases the modulation?
This Gorva enclosure is incandescent and changes colors based on the light angle.
If I recall (been a while since I built mine), the internal trimpot is for gain. Might have to take mine off the wall and mess around a bit, as I always liked the arp setting