Gain Staging

Gain staging is the one topic in recording and live sound that I think most beginners in the industry need to know more about.

Vocabulary is important! You'll want a good understanding of words like level, gain, impedance, and more.

Do you fully understand the difference between gain and volume? How about unity gain? Do you know what balanced vs unbalanced connections are and how they affect gain?

The main "levels" we deal with in audio are "Microphone" level, "instrument" level, and "line level". Microphone level is very low and needs lots of "gain" to become line level. Instrument level needs to be transformed to line level by adjusting the impedance.

Line level is the standard level that audio is listened to when sent to either an amplifer and speakers, or a headphone amplifer and headphones. Line level is also the level at which recording devices record audio. This is true for analog and digital recording equipment. Remember, all digital equipment is analog on the way in and analog on the way out. 

With a microphone, we use a "microphone preamplifier" to increase the gain of the signal up to line level. Once you have added enough gain to the mic signal to bring it up to line level, you can then adjust the volume of the signal. This is usually done with a fader, potentiometer, knob or other device that changes how much of the line level signal is passed through to the next device.

The most important case of when you need to know this is selecting the input level of your recording device. If you are plugging a microphone into the device, you must select mic level input, which will send the signal into a microphone preamplifier. If you are using an external microphone preamplifer, you absolutely must make sure your recording device is set to line level input. Even if turned down enough so that it isn'y clipping or in the red, the line level signal will still sound harshly distorted if run into a microphone preamp.

Think of it this way, the gain knob starts at zero when it is turned all the way down. As you turn it up, you add gain to the signal to help it achieve full line level.

Whereas the volume knob or fader starts at zero (unity), but is zero is usually almost all the way up. The zero mark of a fader or knob will usually be indicated with a bold line. At zero, the fader doesn't turn the volume of the signal up or down, it just passes it through with the same amount of level as provided by the preamp. When you turn the fader down from zero into the negatives, you decrease the volume of the signal. Often faders have a small amount of gain you can add by pushing the fader up past the zero mark.

Contact me if you have questions about signal levels and gain staging and stay tuned for more audio tips on this blog!

Graham @XFO