Intro:
- Setting amplifier gains can be as complicated as using an oscilloscope with a dummy load or simply using a $10 digital multimeter (DMM) and Ohm’s Law. A scope will let you know when the output signal is clipping (distorting). The DMM method assumes you know at what voltage for a given load the output signal will clip. I will discuss the latter.
- Since most (brand-name) amplifiers will do their rated, continuous power per spec, all you need is to connect the multimeter to the speaker output of the amplifier and raise the gain until you achieve the required output voltage while playing a tone through your cd player
- Ohm’s law is used to determine amplifier output voltage. An online calculator can be found here: Ohm's Law Calculator
- Use an attenuated tone, such as -10dB or -5dB as this will allow additional volume for ‘quiet’ tracks. 0dB tones may be used in lieu of attenuated tones IF you listen to heavily compressed music.
- Tones can be downloaded here: Realm of Excursion
- The tone should be in the bandpass of what you are setting the gain for. For example:
- If you are setting subwoofer amp gains, use a 40hz tone.
- If you are setting midrange amp gains, use a 1khz tone.
Setting gains with a DMM:
- Here is a quick guide to properly setting your system gains using nothing more than a DMM.
- Reset all your cd player DSP features, balance, fader, etc to ‘default’.
- Disconnect all speakers to keep from damaging them (and your hearing).
- We will assume your cd player puts out clean, undistorted signal at near maximum. Play your tone (-10dB suggested) and increase the headunit volume to a click or two below max.
- Knowing the amps’ rated power at a given load (ohm) obtained from manufacturer’s spec (assuming they are a reputable brand), use Ohm’s law to determine voltage needed.
- For example, with a 4 ohm load and 100wRMS rating, the output voltage should be 20VRMS.
- Set the DMM to “VAC”, which is AC Voltage.
- Connect the leads of the DMM to the amp’s appropriate speaker output and increase the amp gain until you achieve this voltage
- Repeat for each channel.
You’ve now set up your system to maximize output and performance with a wide variety of music.
Keep in mind, when level matching, you can use your decrease amp gains as opposed to decreasing output level on your DSP. Though, I choose to maximize the gain structure up the chain as much as possible and make adjustments at one place (such as a DSP) just to keep things simple.
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