Reverb after V15
The symptom: after updating from V14 to V15, the reverb’s long fade-out seems to be gone.
The cause: V15 changed effect (and envelope) parameters from a 0–10 scale to 0–100, and kept the stored numbers as they were. A decay of 8, which was near the top on V14, is now 8 out of 100, and that rings for about half a second.
The fix: set reverb Decay to 80–100. On our unit, decay 100 brought the long fade straight back.
On the synth
- Press FX. The screen shows the six effects (Filter, Reverb, Delay, Distortion, Chorus, Phaser). A bright box means the effect is on, a dim box means it is off.
- Turn SELECT to put the blinking dot under Reverb.
- Knob 4 switches it on. Knob 1 picks the type (Room / Hall / Plate), knob 2 sets the mix, and knob 3 sets the decay: turn it all the way up.
- Save the voice if you want to keep the setting.
Over MIDI
Send these on the Effect Channel (default channel 2). The values follow Baud Girl’s FM-1 MIDI guide and M-VAVE’s CC table.
| CC | Reverb parameter | Values |
|---|---|---|
| 4 | On/off | 0 off, anything else on |
| 5 | Type | 0 Room, 1 Hall, 2 Plate |
| 6 | Decay | 0–100 |
| 7 | Mix | 0–100 |
CC 7 is reverb mix, not volume. If a DAW sends CC 7 for track volume on channel 2, it changes the reverb mix instead.
Measurements (V15)
This was measured on one unit over USB:
- Reverb was set by CC, then a 300 ms C4 note was played at velocity 110.
- The FM-1’s own USB audio output was recorded.
- Each figure is the time for the sound to fall 40 dB after the key was released.
| Setting (mix 60) | Time to fall 40 dB |
|---|---|
| Reverb off | 0.08 s |
| Hall, decay 5 | 0.40 s |
| Hall, decay 8 | 0.50 s |
| Hall, decay 10 | 0.72 s |
| Hall, decay 25 | 1.5 s |
| Hall, decay 50 | 2.3 s |
| Hall, decay 75 | 3.7 s |
| Hall, decay 100 | ≈ 5 s (full fade ≈ 7 s) |
| Room, decay 100 | 3.7 s |
| Plate, decay 100 | 4.3 s |
The envelopes changed scale too. If old V14 sounds feel shorter or snappier, raise their attack and release values.
Measure it yourself (Linux)
The FM-1 shows up as a USB audio device. Its capture format is 24-bit packed (S24_3LE), stereo, 44.1 kHz, so record through ALSA’s converting device:
ffmpeg -f alsa -sample_rate 44100 -channels 2 -i plughw:FM1 -c:a pcm_s16le -t 7 take.wav
(hw:FM1 fails, because ffmpeg cannot open the 3-byte format directly.) The sweep script is reverb_sweep.py: it sets the reverb by CC, plays a note, records it and times the tail.
Battery note: on battery, a loud held high note with a long reverb can make the battery bar drop briefly. That is most likely the voltage dipping under the speaker’s load. Check whether it recovers after a minute of silence.