Home » How To » Car Amp Gain [SETTING CHART]

An amp gain setting chart can be used when you want to set amp gain through a multimeter. Set the multimeter probes on the amp output. Increase the gain from zero to reach the target output value mentioned in the chart for the given wattage and resistance readings.

For many people, the concept of “gain” on the amp remains unclear. They consider it a synonym for “volume.” However, that’s not the case. Volume is essentially the setting of “loudness” at the “output” of the amp’s channels. Meanwhile, the gain is the setting of “tone” at the “input” of the amp channels (preamp).

The amp gain setting determines how hard the preamp section of the amp is driven. In other words, when you set the gain control, you manage the distortion level of the tone irrespective of the loudness of the final volume.

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How do I set the gain on the amp?

You can either set the gain on your amp audibly or you can set it via multimeter for more precision (more on these two methods later). When you opt for the latter, you will need a target output voltage reading for the given amp power and the total resistance/impedance of the connected speakers.

EXAMPLE:  The gain should be set at the target output voltage of 20V when the amp is 100W with a total speaker resistance of 4 ohms.

Resistance (Ohms) 4 2 1 2.67 1.5 1.33
Amp Wattage (W)  
100 20V 14.14V 10V 16.33 V 12.25 V 11.55 V
125 22.36V 15.81V 11.18V 18.26 V 13.69 V 12.91 V
150 24.49V 17.32V 12.25V 20 V 15 V 14.15 V
175 26.46V 18.71V 13.23V 21.6 V 16.2 V 15.28 V
200 28.28V 20V 14.14V 23.1 V 17.32 V 16.33 V
225 30V 21.21V 15V 24.5 V 18.37 V 17.32 V
250 31.62V 22.36V 15.81V 25.82 V 19.36 V 18.26 V
275 33.17V 23.45V 16.58V 27.08 V 20.31 V 19.15 V
300 34.64V 24.49V 17.32V 28.29 V 21.21 V 20 V
325 36.06V 25.5V 18.03V 29.44 V 22.08 V 20.82 V
350 37.42V 26.46V 18.71V 30.55 V 22.91 V 21.61 V
375 38.73V 27.39V 19.36V 31.62 V 23.72 V 22.37 V
400 40V 28.28V 20V 32.66 V 24.49 V 23.1 V
425 41.23V 29.15V 20.62V 33.67 V 25.25 V 23.81 V
450 42.43V 30V 21.21V 34.64 V 25.98 V 24.5 V
475 43.59V 30.82V 21.79V 35.59 V 26.69 V 25.17 V
500 44.72V 31.62V 22.36V 36.52 V 27.39 V 25.83 V
550 46.9V 33.17V 23.45V 38.3 V 28.72 V 27.09 V
600 48.99V 34.64V 24.49V 40 V 30 V 28.29 V
650 50.99V 36.06V 25.5V 41.64 V 31.22 V 29.45 V
700 52.92V 37.42V 26.46V 43.21 V 32.4 V 30.56 V
750 54.77V 38.73V 27.36V 44.72 V 33.54 V 31.63 V
800 56.57V 40V 28.28V 46.19 V 34.64 V 32.67 V
850 58.61V 41.23V 29.15V 47.61 V 35.71 V 33.67 V
900 60V 42.43V 30V 48.99 V 36.74 V 34.65 V
950 61.64V 43.59V 30.82V 50.34 V 37.75 V 35.6 V
1000 63.25 V 44.72V 31.62V 51.64 V 38.73 V 36.52 V

If your amp and speaker readings don’t fall in this amp gain setting chart, you can calculate it on your own by using this variation of Ohm’s law.

V= √ (PxR)

Multiply the amp wattage with the total speaker resistance and take its square root, you will find the target output voltage for the right amp gain setting.

How to set amp gain WITH a multimeter

  1. Set the gain, volume, EQ settings, and other boosts on your amp to zero.
  2. Remove speaker wires from the amp and place the multimeter probes on those output ports. Set the meter on AC volts.
  3. Play the test tone on the amp and set the volume at 2/3of its maximum capacity (e.g. if the volume knob has the max reading of 75, set it at 50).
  4. Now slowly start increasing the gain on your amp by moving the gain/level knob clockwise and monitor the voltage reading on the multimeter.
  5. As soon as the voltage reading reaches the value as per the above amp gain setting chart, stop turning the gain/level knob anymore.

How to set amp gain WITHOUT a multimeter

If you are not after the full precision, you can set the amp gain by listening to the sound.

  1. Set the gain, volume, EQ settings, and other boosts on your amp to zero.
  2. Play the test tone on the amp and set the volume at 2/3of its maximum capacity.
  3. Now slowly start increasing the gain on your amp by moving the gain/level knob clockwise and notice the sound for any distortion.
  4. When you think you are hearing the crispest and clearest sound on the given volume setting, stop twisting the gain knob any further.
  5. Now, you can increase the volume to the max and monitor it for any distortion.
  6. If you experience any distortion, twist the knob both ways to find the point where there is no noise.

What does gain do on an amp?

Gain on an amp regulates its preamp section to set the level of distortion in the output sound irrespective of its loudness.

How do I know if my amp gain is too high?

The amp gain is considered high when the amp has reached its full operating power without volume at max. In such a situation, increasing volume drives the amp to clip. To put it simply, if an amp starts clipping when the volume is far from its max limit, its gain is perhaps too high.

Does gain affect wattage?

Yes, the gain is directly proportional to wattage with constant voltage input. If you turn the gain down, the output power of the amp will also go down at the given voltage input.

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