Testgen
Testgen: main parameter page.
A measurement source: TESTGEN replaces its track's audio with a known test signal, so you can measure the Octatrack's own path, a USB audio stream, or another module. It runs with the sequencer stopped and no trigs.
Access
An effect on a track: select the track, press FX1, and pick TESTGEN.
FX1 is the only working slot; an instance on FX2 passes audio through
untouched. Put on FX1, it feeds a known signal into the same track's FX2.
Not in an official remix; build the test remix testgen.
LEVL starts at 0, so choosing TESTGEN makes no sound until you turn it up. Start low: a full-level tone is hard on ears and speakers.
FX1 SETUP with TESTGEN selected: the SINE mode and CHAN.
Operation
MODE on page 2 picks the signal:
| MODE | Signal |
|---|---|
| SINE | a sine at FREQ (with FINE), peak 0 dBFS at LEVL 127 |
| SWEP | an exponential sweep, 20 Hz to 20 kHz over LEN, then 1 s of silence, repeating |
| PINK | pink noise, RMS -14.4 dBFS at LEVL 127 |
| WHIT | white noise, one generator per channel |
| IMPL | one full-scale sample every LEN/4 seconds |
| NEDL | a periodic needle pulse train at FREQ and FINE (a line spectrum) |
| DC | a constant, scaled by LEVL |
- FREQ is a select that shows Hz: the 31 ISO third-octave centres from 20 Hz to 20 kHz plus A440. FINE tunes -200 to +197 cents in 3.125-cent steps.
- LEN is the sweep length in whole seconds, LEN/8 + 1 (32 gives 5 s, 120 gives 16 s).
- CHAN: L+R, L only, R only, L with inverted R (a polarity check), or MONO. With L+R the two noises are independent; MONO gives the same noise on both.
- LEVL steps are 0.5 dB, with 1 at -63 dBFS and 127 at 0 dBFS.
- Changing MODE, FREQ or LEN restarts the signal from its first sample.
- On speakers, start DC at a low LEVL: whether DC reaches the analogue outputs is not measured, and an offset pushes a speaker cone off centre.
Using it
- Level or channel check: SINE at 1 kHz, LEVL 127, then step LEVL to find where a path clips.
- Frequency response: record a whole SWEP period and deconvolve it with its inverse.
- Noise floor: PINK into a third-octave analyser reads flat for a flat path.
- Dropouts and latency: IMPL, then count samples between impulses in a capture.
- Measuring another effect: TESTGEN on FX1 with the effect under test on FX2.
Parameters
| Page | Knob | Range | What it does |
|---|---|---|---|
| 1 | LEVL | 0-127 | output level; 0 is silent (default) |
| 1 | FREQ | 32 steps | SINE and NEDL frequency, default 1 kHz |
| 1 | LEN | 0-127 | sweep length; impulse spacing is a quarter of it |
| 1 | FINE | -64..+63 | SINE and NEDL fine tune |
| 2 | MODE | 7 signals | SINE, SWEP, PINK, WHIT, IMPL, NEDL, DC |
| 2 | CHAN | 5 | L+R, L, R, L/-R, MONO |
Measured through the unit's main out into an audio interface on a MKII (4 Oct 2026): LEVL steps within 0.002 dB, THD at 1 kHz about -94 dB at 0 dBFS.
Screen Reference
Testgen: effect selection and setup parameters.
Status: on hardware: Ignorato's MKII, images OCTABAM4-6 and 10 (remix testgen), 3-4 Oct 2026; 0.1 measured at the main outs; FX1-only in the emulator so far.
Module facts (developers)
Measurement source: a sine, sweep, pink or white noise, impulses, a needle pulse train or DC replace the track's audio.
| Detail | Value |
|---|---|
| Author | Ignorato |
| Category | Effects: on a track |
| Kind | dsp_effect |
| Test status | on hardware: Ignorato's MKII, images OCTABAM4-6 and 10 (remix testgen), 3-4 Oct 2026; 0.1 measured at the main outs; FX1-only in the emulator so far |
| FX2 ID | 0x17 |
| Parameters | LEVL@0, FREQ@1, LEN@2, FINE@3, MODE@6, CHAN@8 |
| Included in | no official remix |
On GitHub: https://github.com/sambanks/octabam/blob/main/modules/testgen/README.md