Setting your gains properly with a multimeter is easier than you think. The gain control is used to level match the amplifier to the head unit. It is not a volume control. Set it once correctly and everything plays nice: the amp isn't stressed, the speakers aren't stressed.
Step 1: Calculate Your Target Voltage
We're looking for the RMS voltage output that corresponds to the amplifier's rated power into your speaker load. Use this formula:
Plug in your amplifier's rated RMS power and your speaker load impedance to get your target.
Step 2: Set Up Your Test Tone
Download the 50 Hz test tone from mtx.com/testtones. It's recorded at the same level as a normal CD. Load it into your head unit, select the track, and loop it.
Step 3: Prepare the Amplifier
- Disconnect the speakers. No need to have them hooked up. The sine wave will stress them unnecessarily.
- Gain all the way down.
- Bass boost all the way down.
- Subsonic filter all the way down.
- Low pass filter all the way up. This gives the widest possible bandwidth before you add the feature set in.
Step 4: Turn Up and Connect Your Meter
Set your multimeter to AC voltage and make sure the range covers your target voltage. Turn the head unit all the way up. Connect the multimeter leads to the amplifier's speaker output terminals.
Step 5: Adjust the Gain
- Slowly turn the gain control up until the meter reads your target voltage.
- Stop. That's your gain set.
Step 6: Finishing Up
Turn the head unit all the way back down. Reconnect your speakers. Put in music you know well and set your filters.
