Singing in the car is probably the second most popular hobby while driving, as playing your favorite music is without a doubt the first. With this detail in mind, you most likely want the sound quality to be the best possible.
Method 1 of 2: Set Gain Audibly
Step 1. Set the volume to zero on the car stereo
You should make sure to turn it on without distorting the sound.
Step 2. Lower the gain of the amplifier to minimum
The amplifier is usually a replacement part that is installed in the trunk of a car or in the back of a truck. You will find a knob labeled "gain." Gain reduction means that the amplifier is not amplifying the signal coming from the stereo head (the part mounted on the instrument panel).
Step 3. Turn on the stereo and play a CD, or tune in to a radio station
You won't be able to hear anything yet, since the volume will be at zero.
Step 4. Turn up the stereo to 2/3 of the maximum volume
This is the best range to use when setting the gain, as it avoids overloading the stereo head. If you overload the stereo head, you could end up sending distorted sounds to the amp. Digital displays make it easy to tell when the volume is at 2/3. However, if you don't have one, you can turn the volume up to maximum (counting the number of laps) and then go back 1/3 of the way. For example, if you turn the volume knob 3 times to reach the maximum volume, you must return it 1 full turn to reach 2/3 of the volume.
Step 5. Turn the gain dial on the amp
Turn it (clockwise) until the sound (music, conversation, test tone, etc.) is as loud as you'd like to hear it, as long as you don't detect any distortion in the sound or overload the speakers. If you detect a distortion, you should lower the gain until it disappears. Some amps have a knob that can be turned by hand, but others may require the use of a screwdriver to adjust the gain.
Step 6. Adjust the volume to a normal level
Now that you've set the gain, you can return to the driver's seat and enjoy your music.
Method 2 of 2: Set the Gain with a Multimeter
Step 1. Calculate the target output voltage
You will need to use a variation of Ohm's law, v = √ (P ∙ R), to calculate the target voltage. To verify the calculations behind this procedure, you can check out an electrical engineering formula wheel. If you don't want to do these calculations, you can use a virtual converter to connect the amplifier power and the speaker resistance and get the target output voltage.
Step 2. Keep in mind that the way you connect the speakers affects the resistance
This detail can drastically change the voltage reading you get and is worth knowing.
- Series-connected speakers are daisy-chained and increase the resistance of the system, decreasing the amount of power each speaker receives. All added speakers will also increase the resistance of the system. The formula to calculate the total resistance for speakers connected in series is Z1 + Z2 + Z3…. = Ztotal, where Z is the resistance of a given speaker.
- For example, if you have 3 speakers with resistance values of 4, 6, and 8 ohms, the total resistance wired in series would be 18 ohms (4 + 6 + 8 = 18).
- The speakers connected in parallel are all connected directly to the amplifier. This detail decreases the resistance of the system, which means that each speaker will receive more power, since you will reduce the resistance of the system by adding speakers to the circuit. Avoid lowering the resistance too much or you will damage the amp. The formula to calculate the total resistance of loudspeakers connected in parallel is a bit more complicated: (Z1 x Z2 x Z3…) / (Z1 + Z2 + Z3…) = Ztotal.
- For example, if you have 2 speakers with 6 and 8 ohm resistors, the calculation would be as follows: 1) Multiply the values: 6 x 8 = 48 ohms. 2) Add the values: 6 + 8 = 14 ohms. 3) Divide the top by the bottom to calculate the total resistance. 48/14 = 3.43 ohms (rounded).
Step 3. Prepare a test tone
You should create a tone that allows you to test the system. You can do this by using a program like audacity or by downloading a suitable ringtone from the internet. You should use a 50-60 Hz sine wave to test a subwoofer or subwoofer amplifier, and use a sine wave that is in the 1000 Hz range to test a mid-range amplifier.
Step 4. Download the tone to an external medium
You should play this tone through your car stereo, so you will need to put it in a CD or MP3 player.
Step 5. Unplug any additional accessories
All speakers, additional amplifiers, etc. they should be unplugged from the back of the amp you plan to test. This will leave only the stereo head (the part mounted on the instrument panel) and the amplifier connected.
Step 6. Turn off all EQ settings on the amp
The amplifier has the ability to filter certain sound bandwidths. To set the gain, you need the maximum bandwidth range, so you must disable the equalizer setting or set it to zero. This will prevent sound waves from leaking out.
Step 7. Set the gain to zero
Usually this means turning the dial to the left as much as possible.
Step 8. Set the multimeter to read AC volts
If your multimeter has multiple settings for AC volts, be sure to choose the range in which the target voltage resides.
Step 9. Play the test tone through the stereo
Insert the CD or connect the MP3 player that contains the test tone. Turn on the stereo. Remember that volume and gain are set to zero, so you won't hear the test tone yet.
Step 10. Turn the stereo up to 2/3 of its maximum volume
This will prevent the stereo head from sending distorted sounds to the amplifier and will be able to adjust the amplifier to a crisp and clean sound.
Step 11. Put the multimeter leads into the output ports of the amplifier
In this way, you will be able to measure the voltage coming out of the amplifier.
Step 12. Raise the gain to reach the target voltage
Turn the gain dial clockwise until the multimeter reads the target voltage. Once you reach the target voltage, the gain will be set to the amplifier.
Step 13. Turn off the stereo
You no longer need the test tone. You can save it to use it later.
Step 14. Plug the accessories back in
You should plug in everything you removed before setting the gain (speakers, amps, etc.).
Step 15. Enjoy your music
This is why you bought the amp in the first place. Then you can start enjoying it!
- Avoid setting the volume to the highest setting as it can distort the sound.
- You must set the gain on multiple amps one at a time.