RDL ST-ACR2 — Bench Certification Protocol

Private working document · Jim Slagle · 27 Aug 2026 · est. 45–60 minutes
Companion signal source: forest.jslagle.net (run it in a browser on the Reaper workstation)

1. Equipment

2. Getting audio onto screw terminals (no soldering)

Option A — instrument cable, no cutting. Take any ¼″ TS (guitar/patch) or 3.5 mm male-male cable. Plug one end into the interface output. The other plug's bare metal is your connection point: wrap a few inches of stripped hookup wire tightly around the sleeve (the long barrel) and tape it; press or tape a second wire firmly against the tip. Tip wire = signal hot; sleeve wire = signal ground. Crude, and entirely adequate for a 45-minute bench test.

Option B — sacrificial cable. Cut any expendable 3.5 mm aux cable in half, strip: tip conductor = hot, sleeve/shield = ground. (Skip earbud cables — their enameled litz wire won't make screw contact.)

Option C — adapter. A "3.5 mm male to screw terminal" adapter (~$7 on Amazon) is the tidy version of Option B if the test waits until one arrives.

Levels: the ST-ACR2 triggers on −30 to 0 dBu — line/headphone output is plenty. Start with system volume around 30% and the app's Level at CAL (−4 dB).

3. Wiring

1. With the 24 V supply unplugged: confirm supply polarity with the meter (DC volts, plug in briefly if unsure: red wire ≈ +24 V relative to black; then unplug again). Red → screw 4 (PWR +), black → screw 5 (PWR ⏚).
2. Jumper across screws 2–3 (see box above).
3. Signal hot (tip) → screw 1. Signal ground (sleeve) → screw 3.
4. Screws 6, 8, and 10–12 remain empty. Nothing connects to 7 or 9 — the meter probes touch those screw heads during the test.

4. Functional test

Record every observation in §7, including what the LED does at each step — write down whatever it shows, without interpreting it.

1. Rest state, powered, silent. Plug in the supply. App stopped, room quiet. Meter on continuity: probe 7–8 → expect beep (closed). Probe 7–9 → expect silence (open). This is the correct de-energized state per the faceplate ("shown de-energized").
2. Baseline the trimmers. Turn SENS 20+ full turns counter-clockwise (minimum sensitivity — soft clicking at the end stop is the clutch, harmless). Turn DELAY 25+ turns counter-clockwise (minimum, ≈5 s).
3. Trigger test. In the app: 1 kHz tone · Continuous · Level = CAL (−4 dB), START. Leave the meter across 7–9. Slowly turn SENS clockwise, counting turns. At some point the relay clicks audibly and 7–9 goes closed (beep). Record the approximate turn count. Give it another half turn of margin.
   If nothing happens even after 25+ turns: raise the system volume to ~70% and repeat. Verify signal is actually present: meter on AC volts across screws 1–3 — expect roughly 0.1–1 V with the tone playing. Signal present but no click across the full SENS range = the unit has genuinely failed; stop here, record it, and the gallery plan proceeds with the iDili.
4. Release test. With the relay closed, press STOP in the app. The relay should release (click; 7–9 open) roughly 5 seconds after the tone stops (DELAY is at minimum).
5. Threshold behaves like a threshold. Drop the app Level to −16 dB. If the relay no longer triggers, turn SENS clockwise until it does. This demonstrates the trimmer is doing its job — the observation that was missing on 21 Aug.
6. Program the production delay (15 s). Switch the app to Burst + stopwatch, 10 s, 1 kHz tone. Press START; the burst triggers the relay; when the burst ends the stopwatch counts up. Press STOP at the release click (watch the meter, or listen). The app reports the measured hold time. Turn DELAY clockwise to lengthen (≈2 s per turn — from the 5 s floor, expect roughly 5 turns) and repeat until two consecutive runs measure 15 ± 1 s. Do not touch DELAY again after this.
7. Filmed verification. Set the app back to Burst 10 s. Position the phone so the frame shows the RDL and the meter (continuity beeper on 7–9). Film one complete cycle: tone starts → click, beep → tone ends → ~15 s of silence → click, release. Thirty seconds of video. This is the exhibit for Bogdan: his unit, doing exactly what it was bought to do.

5. What the outcomes mean

6. Handling note

When the test ends, leave the wiring on screws 4–5 and the 2–3 jumper in place, coil the test leads, and transport the unit gently — the certified state (especially the DELAY setting) is part of what you're bringing to the gallery.

7. Results record

Prepared with AI assistance (Claude, Anthropic) from RDL's ST-ACR Series documentation (891-0031H) and the project record. For Jim's use; not for distribution.