AC/DC coupling on ring and "ring" modulators

DIY STUFF
1

As I cannot find suitable transformers to build a classic transformers/diodes ring modulator, I acquired several other components that can be used to build circuits that result in a similar sounding effect (MC1496, etc).

As usual, I am working my way from the most simple to the more complex designs starting from a simple design that comes from the Korg MS-20 service manual which uses the CD4011 (ARP Odyssey also used the CD4011 to a similar effect).

My build seems correct, although I cannot seem to get the module to work with all the different sources that I tried at the inputs. It works with simple CD40106 oscillators and all kinds of LFOs, but not with the pulse VCO output from my Crave. After thinking about it for a while, I concluded this behaviour must be due to a need for DC coupled inputs. The oscillators and LFOs are all DC coupled, but I suspect that the Crave VCO outputs are not.

If anyone cares to weight in and confirm this, I will just plug the module back to the case and move on to the next “ring” modulator project!

2

There are diodes to half rectify the input signals, of course this will alter the shape of any non pulse wave zero-centered input. Still it seems it ought to do something, unless the peak voltage is too small — 10 Vpp would become 5 Vpp after rectification. In that case just an amplitude boost would maybe fix it.

But maybe your inclination to move on is the right move. This circuit seems simplistic and maybe not worth trying to patch up.