Really easy to build.
The choice is between buffered and un-buffered.
Building a buffered one today.
Here is the breadboarded test circuit.
The basic schematic
The opamp can be a TL084 or TL074
The pinout is identical for both ICs
This particular circuit uses a 074
One change I decided to make was to add a LED to give some sort of indication as to the type of signal this multiple was carrying.
Inspired a bit by the makenoise CV bus
To quote the manual:
"The CV Bus was originally designed for Alessandro Cortini's personal Make Noise system. It provides visual indication of level, rate and polarity for up to 4 control signals that will be shared throughout a patch. ..."
The MN CV bus is I understand passive/unbuffered & those jacks have LEDs built into them.
Here is my 1st perfboard 2HP module.
And the rear
I used a 1K LED resistor. ... experiment a bit.
This LED is standard so will only indicate rate & level.
I'll need to use a bipolar LED to get an indication of polarity.
It works !
I'll build a few versions with different coloured LEDs and try some bipolar ones too.
Bipolar LEDs work well.
(cATHODE to ground)
Use a 470R resistor for green-red LEDs