FULL KIT: Dual LM13700 linear VCA (4HP)
3 in stock.
THIS LISTING IS FOR A KIT - IF YOU WANT A PRE-BUILT MODULE, YOU CAN GET IT here
Another module brought to you by the Department Of Keeping It Simple.
The LM13700 is one of those chips that has been knocking around for years, minding its own business, despite the fact that it is a mind-bogglingly useful and versatile piece of silicon. Granted, it can be a bit of a pain to work with, but it's still useful nonetheless.
This is a dual VCA, each channel of which uses one of the transconductance amplifiers on the 13700. Other than the addition of a couple of linear current sources for CV control this isn't massively different from the circuit you'll find in the datasheet. It works best with signals in the +/-5V range, although it's relatively unbothered by particularly hot CVs from envelope generators.
Is it perfect? No - far from it; depending on your envelope generator there may be a bit of CV bleedthrough, but then if you want ultra-high fidelity then you're probably better off with the THAT2180, which has a unit cost about 10x that of the LM13700 ... that being said, they work well enough that I actually keep a couple in my own system.
Personally, I find that the LM13700 gives a bit of warmth to a sound, but that could just be me ...
This is a full kit - all the necessary componentry is supplied; all you need to do is put it all together - there are a couple of SMD transistors but these are pre-soldered. You can get the BOM and schematic from here: https://github.com/yorkmodular/otavca
The supplied panel is fabricated from 1.6mm FR4 and is dark purple (RAL4007) with gold lettering.