VCA-1.3

Third batch of the old school VCA has landed. A few minor changes have been implemented in the design to get rid of the annoyances I encountered using them. And since I’m the C-level executive of S&C, whatever I say goes! I also empty the trash bin and mop the floor, comes with the perks of being a one-man company. But, more to the point:

  • It’s has a black front panel now with some nice fancy graphics.
  • An extra CV input has been added for all your tremolo or other CV shenanigans. One of the CV’s goes directly to the VCA while the other one has an attenuator. This makes much more sense.
  • The output has been boosted a little bit.

Schematics

updated schematics

Links

DIY info

Check the board you have. v1.2 or v1.3 ( v1.3 has a big white square on it, also, it comes with the black planel with the ‘old school VCA’ graphics)

If you have the board v1.3, just follow the instructions as you find them above. Use 2n3904 transistors.

For v1.2 owners:

Apparently there are different versions of the BC550 transistor which have different pinout configurations. I don’t know who thought that would be a great idea, but here we are. So, here is how things should be oriented: ( E=emitter, B=base, C=collector )

In order to make that work for you, first, check the BC550 resistors you have on hand and determine where the emitter and collector is located. You can check the datasheet of your supplier for this, or ditch the BC550’s and use 2n3904 transistors which don’t have different versions with different pinouts. Then orientate the transistors as shown on the picture on the left.