Peak Programme Meter (PPM)PRO
Understanding and using the built-in audio level LEDs.
Overview
The front panel PPM provides at-a-glance audio level assurance for the audio on IP input 1. It is indicative, not a precision metering instrument.
LED Mapping (dBFS)
| LED State | Color(s) | Approx Level |
|---|---|---|
| Lowest (signal present) | Green | -27 dBFS |
| Next | Green | -21 dBFS |
| Next | Green / Red (dual thresholds) | -15 / -3 dBFS |
| Top (tri-color) | Green / Orange / Red | -12 / -9 / -6 dBFS |
To meet EBU R68:
- 0 dB (reference) ≈ -18 dBFS (two green LEDs)
- Normal program peaks ≤ -12 dBFS (max three greens)
- Peaks must not reach orange (-9 dBFS)
Distortion Indicator
All four LEDs blinking red → Detected audio distortion.
Best Practices
- Set encoder audio gain so regular speech hovers around -18 dBFS (two greens) with peaks brushing third LED.
- Investigate any persistent orange/red—likely clipping chain upstream.
Limitations
- Single input scope (IP input 1 only).
- Not a substitute for calibrated ingest meters.