Understand a constant-voltage line
In a 70 or 100 V system, each transducer transformer presents a selectable power tap. The sum of those taps is the starting point for amplifier sizing. Amplifier outputs and transformers must match the chosen line voltage.
Do not confuse this topology with parallel low-impedance wiring. Directly connecting a low-impedance transducer to a 100 V line without a suitable transformer and design can cause damage.
Add the tap loads
Twelve transducers set to 6 W present a nominal 72 W line load. Set each tap to the needs of its area; the highest tap is not automatically the correct choice.
Pload = Σ (count × tap watts)Define the reserve convention
If 20% of amplifier capacity must remain unused, the load is limited to 80% of rated capacity: a 72 W load therefore needs at least 90 W. Adding 20% to the load instead gives 86.4 W. These are different reserve conventions.
Pamp ≥ Pload / (1 − reserve fraction)Include the cable
Loop length, conductor cross-section and material determine line resistance. Cable dissipation reduces power reaching the load. Record each branch’s load and length separately on long runs.
Total line wattage alone does not determine conductor size. Use the cable-loss tool alongside the load estimate, then check routing, terminations and applicable installation requirements.
Check before commissioning
Prepare a schedule of counts, group taps, zone loads and cable routes. After installation, verify wiring and actual line load with suitable equipment; do not test a circuit connected to a powered amplifier.
- Match amplifier line voltage and transformer ratings.
- Keep each channel load within its rating.
- Document reserve, cable losses and future expansion separately.