Car Amp Gain [SETTING CHART]

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.

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.