Measuring Amplifier Gain

Gain is a matching knob, not a loudness knob. Use this page to match the source and amp cleanly so the system makes rated output without getting noisy or clipping early.

Tiny Version

Set the source clean, pick the right test tone, then adjust the gain until the amplifier reaches the right output cleanly.

Setup Checklist

• Source EQ flat, loudness off, bass boost off, and processing disabled unless it is part of the final tune.
• Know the source clip point before setting the amp.
• Load the correct test tone for the channel you are setting.
• Subwoofer channels usually use a low-frequency tone such as 40 to 50 Hz. Full-range channels usually use a midband tone such as 1 kHz.

Target Voltage Formula

V_target = sqrt(P_rated x Z_speaker)

Beginner Path: True-RMS DMM

1. Disconnect the speaker from the amp channel you are setting.
2. Connect the true-RMS DMM across the amplifier speaker output.
3. Play the correct test tone from the source.
4. Raise the source to its known clean limit.
5. Turn the gain up until the meter reads the target voltage.

Deep Path: Oscilloscope

1. Connect the scope across the amplifier output.
2. Play the correct test tone and raise the source to its known clean limit.
3. Increase gain until the waveform reaches the target voltage without flattening.
4. If flat tops or bottoms appear first, back down until the waveform is clean again.

Common Mistakes

• More gain does not make the system stronger. It can make noise and clipping worse.
• Using the wrong test tone for the channel can give you a misleading result.
• Setting gain before you know the source clip point makes the whole number chain less trustworthy.