Volume and gain – musicians use these two all the time but if you ask them to explain to you the differences among them and how they relate to each other, chances are they wouldn’t even know where to begin. Sure, you don’t need to know exactly how to explain volume and gain in order to make the most out of it — you mess around with the two into you get the right amount of loudness and distortion – but it never hurts to know. And if you happen to be in the market for a new amp, the information is more valuable since volume and gain are closely related.
But before we get into that, let’s start off with some amplifier basics. A guitar amp can be thought of as a device that has two stages. A relatively weak signal goes from your instrument into the first stage, where it is processed and handed to the second stage, which boosts it into a strong signal—the sound that then comes out of the speakers and rocks the house.
That first stage is the preamp stage. On some amps, you can control the level or strength of the signal sent through this first stage; this control is called “gain” (also often labeled as “drive”). Gain can be thought of as the input volume to the preamp stage (gain adjustments can produce changes in overall volume, which might account for some of the confusion between the terms), although it’s more of a tone control than a volume control. Your gain setting determines how hard you’re driving the preamp section of your amp. Setting the gain control sets the level of distortion in your tone, regardless of how loud the final volume is set.
What this means is that your gain setting determines how clean or dirty your sound is regardless of the master volume setting. You can set the gain high for a dirty tone, but set the overall volume of that dirty tone from near silent to near deafening using the master volume control.
Master volume is an entirely separate entity that lives in the second stage of your amp, the power amp section. It provides the muscle. Think of it this way: the preamp (and gain control) provides the shape of the sound; the power amp provides the overall strength of the sound.
In amps with only a single volume control (and no gain control), that volume control is usually placed early in the signal path—in the preamp stage—thus controlling both volume and gain. And there you have it – the difference between volume and gain!
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What are some of the ways you use the volume knob aside from how loud you want your guitar?