Happy Nerding FM Aid
Analog through-zero linear FM for any signal
4 HP Eurorack module
FM AID is an analog Through-Zero Linear Frequency Modulation module that enables classic digital-style FM synthesis without aliasing artifacts. Any signal can serve as carrier or modulator, producing sine, triangle, sawtooth, and square outputs with continuously variable FM depth. Its musical character ranges from clean harmonic enrichment to complex wave-folding textures and analog noise generation.
Features
- Through-Zero Linear Frequency Modulation in fully analog circuit
- No digital aliasing artifacts
- Any signal can be used as carrier or modulator
- Four simultaneous outputs: sine, triangle, sawtooth, square
- CAR input normalled to MOD input for single-source operation
- FM depth (modulation index) knob with 0-10 range
- Bipolar CV knob for external FM depth modulation (-5 to +5 scale)
- CV input accepts AC or DC signals at -5V to +5V
- Onboard trimmer for carrier input level calibration
- Accepts carrier inputs from -1V/+1V up to -12V/+12V via trimmer adjustment
- Feedback patching enables analog noise generation
- Reverse polarity protection
Controls & Jacks (13)
- CV — Attenuverter for the CV input — scales and inverts external modulation of the FM depth.
- FM — Controls the FM modulation depth — sets how strongly the modulator affects the carrier frequency.
- CV Input — CV input for modulating the FM depth externally.
- MOD — Modulator input — connect the modulating oscillator here.
- CAR — Carrier input — connect the carrier oscillator here.
- Sine — Sine wave FM output from the modulator side.
- Triangle — Triangle wave FM output from the modulator side.
- Sawtooth — Sawtooth wave FM output from the modulator side.
- Square — Square wave FM output from the modulator side.
- Sine 2 — Sine wave FM output from the carrier side.
- Triangle 2 — Triangle wave FM output from the carrier side.
- Sawtooth 2 — Sawtooth wave FM output from the carrier side.
- Square 2 — Square wave FM output from the carrier side.
How-To Guides
- Classic FM Synthesis Patch
- Single-Source Wave Folding
- Velocity-Controlled FM Brightness
- Audio Rate CV for Sidebands
- FM Feedback Noise Patch
- Hard-Sync FM Static Tone
- Recovering Bass Fundamentals in Dense FM
- Pitch-Dependent FM Timbre Mapping
- LFO FM Wobble and Timbral Tremolo
- Calibrating the Carrier Input Trimmer
Explore the interactive FM Aid panel on BleepDex — tap any control to learn what it does.
