Live Sound Power Requirements: Electrical Planning for Shows

Understanding live sound power requirements prevents blown circuits, equipment damage, and show-stopping electrical failures. Audio equipment draws significant current, and venues vary widely in electrical infrastructure. Calculating power needs before arrival enables proper planning and reveals potential problems before they become emergencies.

Basic Electrical Concepts

Watts measure power consumption. Audio equipment specifications list wattage ratings indicating how much electrical power the device uses. These ratings guide power planning calculations.

Amperage measures current flow—the amount of electricity moving through wires. Circuit breakers trip when amperage exceeds their rating, protecting wiring from overheating. Standard US circuits provide 15 or 20 amps at 120 volts.

Voltage represents electrical pressure. North American standard wall voltage is 120 volts. Some high-power equipment uses 208 or 240 volts for efficiency, reducing amperage requirements for equivalent power.

The relationship between watts, volts, and amps follows Ohm’s Law: Watts = Volts × Amps. A 1,200-watt amplifier on a 120-volt circuit draws 10 amps (1200 ÷ 120 = 10).

Calculating System Power Draw

Powered speakers list power consumption in specifications. A typical powered 12-inch speaker draws 200-400 watts. Two speakers plus a powered subwoofer might total 800-1,200 watts, drawing 7-10 amps from a standard circuit.

Mixers draw modest power, typically 20-100 watts depending on size. A compact analog mixer might draw under 30 watts; a large digital console could draw several hundred.

Amplifiers for passive speakers consume substantial power. A 1,000-watt per channel amplifier might draw 1,500-2,000 watts at full output, requiring dedicated circuits or high-current connections.

Backline amplifiers add to total draw. Guitar amps range from 15 watts for small tube combos to several hundred watts for high-power solid-state heads. Bass amps commonly run 300-800 watts.

Circuit Capacity Planning

Standard 15-amp circuits safely handle 1,440 watts (15 × 120 × 80% safety factor). Standard 20-amp circuits handle 1,920 watts. Exceeding these limits trips breakers, potentially mid-performance.

Separate circuits for different equipment groups prevent cascade failures. FOH system on one circuit, monitors on another, and backline on a third distributes load and isolates problems.

Identify circuit breaker locations before soundcheck. Knowing where breakers are enables quick reset if one trips. Mark breakers serving performance areas for easy identification.

Older venues may have undersized or aging electrical systems. Buildings with 60-amp service total struggle with modern sound system demands. Assess venue capacity before committing to shows.

Power Distribution Equipment

Power strips rated for the connected load safely handle multiple devices. Use power strips rated for 15 or 20 amps matching the circuit capacity. Avoid daisy-chaining strips, which creates fire hazards.

Power conditioners from Furman, APC, and similar manufacturers provide surge protection and noise filtering. These units protect sensitive digital equipment from voltage spikes and electrical noise. Rackmount power conditioners integrate with mixer racks.

Heavy-duty extension cables rated for the load prevent voltage drop over distance. Long runs of undersized cable cause equipment to receive insufficient voltage, potentially causing damage or malfunction. Use 12 AWG or heavier cable for runs over 50 feet.

Generators for outdoor or temporary venues require proper sizing and conditioning. Inverter generators produce cleaner power suitable for audio equipment. Standard generators may require power conditioning to reduce noise and voltage fluctuation.

Avoiding Ground Loops

Ground loops occur when equipment connects to different ground points, creating a loop that picks up electromagnetic interference. The symptom is persistent hum at 60 Hz and harmonics.

Connecting all audio equipment to the same electrical circuit eliminates most ground loops. The common ground reference prevents potential differences that cause hum.

Ground lift switches on DI boxes interrupt the ground connection at the input stage, breaking ground loops without compromising safety ground connections on power cables.

Hum eliminators from Ebtech, Morley, and others insert between problem devices to break ground loops. These devices use transformers to pass audio while interrupting ground paths.

Safe Practices

Never defeat the ground pin on three-prong plugs. The ground connection protects against electrocution if equipment faults. Equipment operating on two-prong connections presents shock hazards, especially on stages with metal microphones and wet floors.

Inspect cables for damage before each use. Frayed insulation, exposed conductors, and damaged plugs create shock and fire hazards. Replace damaged cables rather than repairing them.

Keep electrical connections dry. Outdoor events require waterproof connections and routing that prevents water accumulation near electrical equipment. Cover open connections with electrical tape.

Position generators downwind and away from audience and performer areas. Generator exhaust contains carbon monoxide, which is colorless and odorless. Adequate ventilation prevents dangerous accumulation.

Planning for Problems

Carry spare fuses for equipment that uses them. Many amplifiers include user-replaceable fuses. Having appropriate replacements enables quick recovery from fuse failures.

Identify alternate power sources at venues. An outlet in a different area might run on a separate circuit. Extension cables long enough to reach alternate sources provide options when primary circuits fail.

Communicate power requirements to venues in advance. Technical riders should specify power needs including total wattage, number of circuits, and any special requirements. Advance notice allows venues to prepare appropriately.

Load-in assessment includes verifying power availability matches expectations. Check outlets with a tester to confirm proper wiring. Measure voltage under load to verify stability.