The Balanced Modulator combines to audio signals to create interesting overtones, not unlike a ring modulator but lacking many sidebands.
The circuit here is based on the Yusynth Double Balanced Modulator with minor tweaks to make it more Eurorack friendly. The changes I've made are thus:
- Selected resistors appropriate for +/-12V rails,
- Added polarity protection so that a backward power header doesn't fry anything (twin series schotty diodes: BAT54SL),
- Full surface mount design,
- Reduced module to a single balanced modulator.
The Yusynth page is a treasure trove of information about this circuit that I am too amateur to claim as my own; please read that outstanding page before using this circuit. The page provides many details and other implementations of this circuit that you may find suitable.
The KiCAD project here uses the library/footprints found in my companion repo.
12hp on an Intellijel 1U rack.
Jacks:
- Carrier Signal:
A sin(f_1 t) - Modulating Signal:
B sin(f_2 t)
Output jack for modulated signal: A sin((f_1 + f_2) t) + A sin((f_1 - f_2) t)
There are three sets of jumpers for setting whether the inputs and outputs will be AC or DC coupled. Use three jumpers to choose how the signals will be coupled.
TBD
There are part numbers in the BOM for many of the parts (not for basic passives though) at the following vendors:
- Mouser: Needs no introduction. Get your ICs from here (or digikey).
- Tayda Electronics: Good supplier for passive components; audio jacks, and potentiometers. Their audio jacks are slightly smaller than the thonkiconn from thonk.
- Love My Switches: Has really good knobs to go on those potentiometers!
- OSHPark: Fast and (relatively) cheap PCB manufacturer.