When you are playing around with your guitar at home or doing some recording, it can take a bit of work to get the right tone, you play about with the knobs and settings, get the sound you are looking for and let rip. When you are playing live, things can get more complicated, especially if you require different sounds for different songs. You set your pedals up at home, everything sounds right, you get to the gig and your tone is suddenly a disaster. What went wrong?
Well, if you play live then you have to expect a certain amount of problems. No two halls sound alike and many things will affect your tone, anything from the amount of people at the venue to the placement and volume of other band members, even the arrangement of the furniture. You'll never find a default setup that sounds right every time, you will always need to tweak your sound in one way or another but there's one very important element to your setup that will alter your sound drastically if you don't understand how the signal from your stomp boxes interact with the settings on your amp ... volume!
When the venue fills up, band members often crank up, so you turn up your amp to compete and find all your FX now sound like a mess, too much reverb, too much delay, the chorus has disappeared and your solos have become inaudible. Sound familiar? Chances are you've turned up the gain on the amp and everything has changed. This problem occurs as a result of badly matched gain staging. There's no quick fix for this problem, the best you can do is understand what it is so that when it occurs you have a better chance of dealing with it. Not knowing about it just leaves you guessing what knob to twiddle.
Most amps have at least two volume controls, gain and main volume. If your amp has two channels then you'll likely have two or more gains as well as the main volume. Now I don't want to bore you with the technical details so I'll give you a basic explanation of what the differences are.
Guitar amplifiers have two main stages, the pre-amp and the main amp. Two channel guitar amps will have two pre-amps and one main amp. You can think about this as two separate amplifiers in one box (or three for a two channel amp). The reason for this two stage idea is because guitarists like to crank up the volume and overdrive the signal to create distortion. For everything else this is bad news but for loud guitar it's extremely common. So the reason we guitarists get two volumes is so that we can have the amp cranked right up without having it blasting out at full volume. We can adjust the pre-amp (gain) to give us the amount of distortion we want, and the main amp gives us an overall volume so that we can get the right overall level.
This idea works well when the guitar is plugged in directly to the amplifier but when you place something like a multi effects pedal between the guitar and amp, the amp's gain setting has a large affect on the resulting sound. Ideally, once you have got the sound you want from the pedal then the gain on the amp should stay where it is. If later in the gig you decide to use the gain for getting a bit more volume then the sound will change drastically. If you are all out of main volume and forced to turn up the gain, you might find you now need to change the patch settings on the pedal as well.
Effects such as delay, reverb and modulation usually sound best if they are placed in the chain after any distortion. Your pedal is probably setup this way and works well internally but as soon as you turn up the gain on the amp, you introduce more distortion after the pedal. This will often reinforce effects like delay, making them sound much louder and messier than they would with a lower gain level. This can't really be explained any further without getting too technical so the best thing to do is experiment with various pedal patches and listen how they are affected with varying gain levels.
One more thing worth noting. If you use an overdrive or distortion to boost your volume over guitar solos then the gain will have a huge impact on the amount of boost you get. A guitar amp's pre-amp section can only take so much before it max's out on available headroom. What this means is the higher the level, the lower the amount of boost. Again, try it and listen. Set the main volume very low so that you don't blast the house out. Now set your overdrive pedal to max and the guitar amp's gain quite low. When you switch in the pedal you'll notice a massive volume boost. As you turn the gain up higher, the amount of boost gets smaller until eventually the pedal seems to make no difference at all. If you are using this boost to your advantage in live situations then this is also something you must be aware of.
