Home >> Hobbies >> Other Hobbies

How to Calculate an Audio Mixer Circuit

In audio mixer circuits, a component called an operational amplifier, or op amp, plays a central role. A mixer combines two or more audio signals electronically in varying proportions to produce a musically pleasing result. To accomplish this, the op performs several mathematical operations. First, it adds signals together and then it multiplies the result by a common factor to produce signal gain. When designing a mixer, a technician adds the expected values of audio signals and then finds a gain factor that produces clean, undistorted sound.

Things You'll Need

Calculator

Instructions

- 1
  Input the op amp's power supply voltage into the calculator. Press the ̶0;multiply̶1; key, enter ̶0;.8̶1; and press the ̶0;equals̶1; key. Write the result down or press the ̶0;Memory Recall̶1; or equivalent key to store it in the calculator̵7;s memory. For example, if the op runs on 15 volts, 15 times .8 equals 12 volts.
- 2
  Enter the number of inputs for the mixer and press the ̶0;multiply̶1; key. Enter the number ̶0;50,000̶1; and press the ̶0;multiply̶1; key. For example, your mixer has five inputs, so 50,000 times 5 equals 250,000.
- 3
  Press the ̶0;Memory Recall̶1; key to recall the stored result of the earlier calculation or enter the figure manually from what you wrote down. Press the ̶0;equals̶1; key. The result is the value in ohms for each input resistor that feeds a signal to the op amp. Continuing the example, 250,000 divided by 12 equals 20,833. The op amp̵7;s feedback resistor is 50,000 ohms and each input resistor becomes 20,000 ohms; this is the closest available value for standard resistors.

Other Hobbies