In some cases, it will be necessary to plug your guitar amplifier into a mixing board. When you are recording guitar, the mixer sends the sound from the guitar amplifier into the recording device, whether it is a tape or a computer. When you play a show, the mixer functions in a similar fashion, but the sound is then sent to a public address system for the audience to hear. The most common way to plug a guitar amp into a mixer is through the use of a microphone, but you can plug it directly into a channel using the direct out as well.
Turn the two main sliders down on the mixing board. This will prevent any popping or excessive loud noises when you are hooking up the guitar amplifier to the mixing board for live or studio use. The main sliders control the input that is sent to the main outputs of the mixing board.
Set the guitar amplifier to the sound you would like to record or amplify. Plugging your guitar amp will allow you to record it or send the sound to a public address, or P.A. system for a concert or event. Set the volume you will need as well as the various equalization points for the tone. Set the amount of gain you will use for each channel as many guitar amplifiers have more than one channel.
Plug an instrument cable into the direct out output, which is located on the back of the amplifier. This sends the signal to an outside source. Some amplifiers have speaker simulators for use with the direct output, but most do not. The direct out will work in a pinch when a microphone is not available. Plug the other end of the cable into the input of a channel on the mixing board.
Place a microphone in front of one of the speakers on the guitar amplifier. Plug a microphone cable into the microphone and plug the other end into a channel on the mixer. Use a different channel if you are using both a microphone and the direct out of the amplifier.
Slowly raise the sliders of the individual channel or channels while someone plays the guitar. Raise the level until the clip lights on each channel light up on notes that are hit hard. Lower the slider if the channel is constantly clipping. This will let you know the signal is strong.
Raise the master faders slowly as well until the sound is strong through the P.A. or in your headphones. Look for clipping on the main LEDs as well. Keep the volume high and the sound of the amplifier clear. Listen for distortion or unwanted noise and make any volume adjustments as necessary.