Moog Rogue: adding a Filter CV input
The Rogue in its original form includes keyboard CV and Gate inputs and outputs. It’s a slightly odd arrangement of TRS (stereo) jacks – one for the CV, with the input on one terminal and the output on another, plus signal ground, while the Gate connector has an even more awkward arrangement of short-to-ground on one terminal and positive trigger on another, either of which can act as input or output. It’s not great. But it does work, providing you have the right cables.
Rather than split these into separate jacks, which would be a handy mod, I just use custom made cables for my interconnects between CV devices. However, the Rogue lacks a CV input for the filter, which I thought might make a useful addition. It’s a simple enough job.
I decided to use a 3.5mm minijack for the sake of convenience. Pick a spot on the rear panel and drill a suitable hole:
I had a switched 3.5mm mono socket to hand, so used that:
Solder a ground wire from the appropriate jack terminal to the Rogue’s jack PCB. Its large solder plane is suitable and easy to work with:
The filter CV input requires a 45k3 resistor to give the same scaling as the keyboard. As presented here, there is no onboard scaling, so if you want to run the input as anything other than 100% follow, use an external amplifier/attentuator. It would also be possible to build such a circuit into the Rogue, but I chose not to for simplicity.
The other end of that blue wire goes to the filter CV node on the main PCB. Rather than outline it on the schematic, I’ll just show you where that is on the board. This is the point where various filter CV inputs are summed. It’s an easy job to solder a wire at the top of this area:
Here’s a wider shot. Note the longer black wire is a previous bodge and not related to these mods and repairs:
I used a Dymo labeller to add the finishing touch to the back panel:
Hey presto! A filter CV input scaled at the same degree as the keyboard. I use a Kenton MIDI-CV interface, which has an auxiliary output for filter CVs, amongst other things, so this little mod should come in quite handy.