Measuring Amplifier Gain

Procedure for setting and verifying gain:

Equipment: Oscilloscope or DMM (true RMS)

1. Connect oscilloscope across amplifier speaker output (or DMM set to AC RMS)
2. Apply 0 dBFS 1 kHz sine wave to head unit
3. Set head unit to 75% volume
4. Measure amplifier input voltage (RCA signal level)
5. Adjust gain until output = √(Prated × Zspeaker) volts

Clipping detection:

On oscilloscope: Flat tops or bottoms on sine wave = clipping. On music: Use 0 dBFS test tone — any waveform distortion visible at rated output indicates clipping.

Input sensitivity calculation:

V_input_needed = V_output_at_rated_power / Gain_linear

Most car amplifiers have input sensitivity range of 200 mV to 4–6V RMS, adjustable by gain control.