Happy Nerding — FM AID
Download the FM AID 2020 Manual (PDF)
Happy Nerding FM AID (2020) — Cheat Sheet
Overview
FM AID is an analog Eurorack module for through-zero linear FM synthesis. Any signal can be used as Carrier or Modulator for wild, aliasing-free wave shaping and FM tones. Saw-tooth input recommended for "classic" FM outputs, but all source types yield unique results.
Panel Reference
Top Controls
- FM Knob: Sets modulation depth (FM index).
- CV Knob: Bipolar attenuator for CV input, mixes with FM knob.
Jacks
- CV IN
- Voltage Range: -5V to +5V (accepts AC or DC)
- Purpose: Controls FM depth (modulation index) via external voltage.
- MOD IN (Modulator)
- Voltage Range: Preferably -5V to +5V (accepts -1V to +1V up to -12V to +12V with trimmer adjustment)
- Purpose: Signal input that frequency-modulates the Carrier.
- Note: Carrier is normalled to Mod if no patch present.
- CAR IN (Carrier)
- Voltage Range: Preferably -5V to +5V (trimmable up to ±12V)
- Purpose: Main signal to be modulated.
- Note: Sawtooth gives most "classic" FM outputs.
- Outputs (All: -5V to +5V, 1kΩ impedance)
- Sine: Smoothest output, classic sine when fed sawtooth.
- Triangle: Brighter than sine.
- Sawtooth: Bright, reproduces saw input when fed saw.
- Square: Brightest, gives square when fed saw.
Quick Start
- Install in 4HP space, connect 10–16 pin power (red stripe = -12V).
- Feed sawtooth to CAR IN for "classic" FM output shapes.
- Plug MOD IN for external modulation, or use default (normalled) for wavefolding.
- Use FM knob to set FM index (intensity).
- Use CV knob to add/shape modulation from the CV input.
- Patch outputs to get Sine, Triangle, Saw, or Square variants.
Tricks
- Self-patch any output to MOD IN for feedback tones and analog noise.
- Patch velocity or pitch CV to CV IN for dynamic, keyboard-driven timbres.
- Hard-sync both carrier & modulator sources to eliminate frequency beating.
- Lower carrier/modulator octave or switch to sine/triangle to restore low end if the main tone gets lost at high FM depth.
Calibration
- Onboard trimmer adapts module for input voltage ranges from ±5V to ±12V.
- To calibrate: Feed saw into Carrier, set FM fully CCW, monitor Saw output, and trim for cleanest output.
Input/Output & Control Summary Table
| Function |
Jack/Control |
Type |
Typical Voltage Range |
Description |
| FM depth |
FM knob |
Knob |
Manual |
Sets FM index |
| CV attenuator |
CV knob |
Knob |
Manual |
Mixes CV with FM knob |
| FM depth CV |
CV IN |
Jack |
-5V to +5V |
Modulates FM depth |
| Modulator |
MOD IN |
Jack |
-5V to +5V (adj. up to ±12V) |
Frequency modulation input |
| Carrier |
CAR IN |
Jack |
-5V to +5V (adj. up to ±12V) |
Source to be FM-modulated |
| Sine out |
Output |
Jack |
-5V to +5V |
Sine-like output |
| Triangle out |
Output |
Jack |
-5V to +5V |
Triangle-like output |
| Sawtooth out |
Output |
Jack |
-5V to +5V |
Sawtooth output |
| Square out |
Output |
Jack |
-5V to +5V |
Square output |
Generated With Eurorack Processor