A/C - D/C switches on Shapechanger and Navigator


#1

Can someone help me understand how these switches work? I’m not sure I see a difference in my images when manipulating them while various CV sources are plugged in. Perhaps it just depends on whether you’re using audio or CV to modulate?
Jim


#2

I asked Jonah about this at KnobCon and he really helped clarify this for me. A/C refers to alternating current, so basically that switch lets you use “through zero” sources that alternate between positive and negative voltages. The way I like to think of it is that, with AC selected, you can “turn the knob” both left and right with your CV source, so long as that source is alternating.


#3

James’ answer is good! To put it another way, turning AC mode on is removing any slow moving content from your modulation source. It’s a high pass filter with its cutoff at frame rate.

With a positive DC biased signal (like 0-1V video) the signal is always additive. If you add it to a mix, the mix becomes brighter. If you subtract it from a mix, the mix becomes darker. You are modulating brightness.

When you AC couple this signal, rising voltages will add, but falling voltages will subtract, since the relative DC offset (gray level) is gone. This gives the behavior with the modulation source adding brightness when it rises and subtracting brightness when it falls. In other words, you are now modulating contrast.


Pendulum AC/DC Switch
#4

Lars and James – thank you kindly. I want to learn as much as I can about this stuff, as it’s all the more exciting with some technical understanding. Whatever resources you can point me to for reading material would be greatly appreciated. I’m having great fun with my new LZX stuff and just treasure these incredible modules.
Jim