Bridging Channels on AudioControl CM-Series Amps
Bridging Channels on AudioControl CM-Series Amps
The CM2-750, CM3-750 and CM4-750 amplifiers support channel bridging for more output per zone — particularly useful for 100V line speaker distribution. This is the installer's wiring and configuration reference. Read the impedance warning before connecting anything.
Physical connection
- CM2-750 and CM3-750: bridge by taking the positive (+) terminals of Channel 1 and Channel 2. On the CM3-750, Channel 3 cannot be used as a bridged output.
- CM4-750: two independent bridge options — bridge the + terminals of Channels 1 & 2, or the + terminals of Channels 3 & 4.
DIP switch — set for the speaker type
Each channel has an A/B DIP switch:
- A (UP): 70V speakers, or 8-ohm low-impedance speakers
- B (DOWN): 100V speakers
For UK commercial and multi-room distribution this will usually be B (DOWN) for 100V line.
Impedance — do not skip this
A bridged output has a minimum impedance of 8 ohms. Do not connect a 4-ohm speaker to a bridged channel. Doing so risks damaging the amplifier.
Enable the bridge in the web interface
This step is easy to miss and silences the zone if skipped:
- Open the Global settings (gear icon).
- Go to Amplifier settings > Bridge.
- Tick the box next to the bridged outputs.
With the box ticked, both channels output identical audio at equal power. If it is left unticked, no audio reaches the bridged zones — even though the wiring is correct. If a freshly bridged zone is dead on first power-up, check this box first.
This article was adapted from AudioControl's original guidance: "How to bridge amp channels on the CM-series 70 Volt amplifiers" — https://support.avproglobal.com/portal/en/kb/articles/how-to-bridge-amp-channels-on-the-cm-series-70-volt-amplifiers-14-11-2025 Habitech-edited for UK trade installer context. Original © AudioControl (via AVPro Global KB).