As a guitar player, I’ve spent countless hours turning the knobs on my amp trying to dial in the perfect tone. And one knob that has always confused me is the gain control. What exactly does gain do on a guitar amp? And how is it different from volume?
In this article, I’ll explain exactly what gain is, how it affects your tone, and how to use it to get the sounds you want. Whether you play rock, blues, country or jazz, understanding gain is crucial for dialling in your amp.
The Short Answer
Gain controls the level of the guitar signal going into the preamp section of your amplifier. It’s measured in ratios like “Unity Gain” or decibels. Higher gain boosts the strength of the guitar signal before it reaches the power amp. This allows you to overdrive the preamp tubes, creating distortion if you want it.
Gain increases the amplitude or voltage of your guitar signal. More gain makes your guitar louder at a given volume setting. But gain is not the same as volume, which controls the power amp section.
The Long Answer
Now let’s dig into the details. Gain refers to the amount of boost applied to the guitar signal as it enters the preamp section of your amp. This part is called the “preamp” because it amplifies your guitar signal before it reaches the power amp section.
With tube amps, increasing the gain drives the preamp tubes harder, causing them to compress and distort the signal. This is how overdriven and distorted sounds are created. Solid state amps emulate this effect using analog circuits and digital modeling.
Gain is measured in decibels (dB) to indicate how much boost is applied. “Unity gain” means no boost at all—the signal enters the preamp at its original strength. Higher gain settings like +20dB or +40dB dramatically boost the signal level entering the preamp.
Gain vs Distortion
Gain and distortion are closely related, but not the same thing. Here’s the key difference:
- Gain controls signal strength entering the preamp
- Distortion occurs when the preamp tubes are driven past their clean headroom limit
Adding gain does not necessarily create distortion. You can boost the signal without going past the point where the preamp tubes compress and distort the sound waves.
But increasing the gain does take you closer to that point. Once the signal becomes too hot for the preamp to handle cleanly, the peaks of the waves get compressed and clipped off. This distorts the signal and shapes the sound waves, adding overdrive.
So in summary:
- Gain boosts signal strength
- Too much gain overloads the preamp tubes
- Overloading the tubes causes distortion
The Difference Between Gain and Volume
Gain and volume controls operate at different stages of an amp’s circuitry. Think of an amp in two parts:
- Preamp section
- Power amp section
Gain works in the preamp stage. It controls how strong the signal is when it leaves the preamp to go to the power amp. The preamp is where you shape the tone.
Volume controls the power amp section. This sets how loud the amplified signal coming out of the preamp will be. Volume determines the final output level you hear through the speakers.
So gain causes volume, but they are not the same control. Gain happens first in the preamp, which then feeds the power amp controlled by the volume knobs.
Master Volume vs Preamp Volume
Many amps split volume control into two knobs:
- Preamp volume
- Master volume
Preamp volume operates right after the preamp gain to control the signal level going into the power amp. Master volume is the final output level.
Having separate preamp and master volumes allows you to overdrive the preamp without being overly loud. For example:
- Set high preamp gain
- Max the preamp volume to overdrive the tubes
- Lower the master volume to reduce overall output level
This setup allows for cranked tube distortion at lower volumes, perfect for home playing and recording. The master volume does not add more overdrive, it just controls loudness.
High-Gain vs Low-Gain Amps
Understanding the difference between high-gain and low-gain amps will help you choose the right amp for your music. The main differences come down to gain staging and headroom.
Low-Gain Amps
Low-gain amps are designed for clean tones. They have plenty of “headroom”, meaning the preamp can accommodate hotter signals without breaking up and distorting.
Some key characteristics of low-gain guitar amps:
- Higher clean headroom in preamp
- Gain knob mainly controls volume, not distortion
- Often higher wattage ratings like 40W to 100W
- Usually no master volume control
- Popular with jazz, country, classic rock players
Fender amps like the Twin Reverb and Bassman are classic examples of low-gain designs focused on clean tones. At lower gain settings you can turn them up very loud while retaining clean headroom.
High-Gain Amps
High-gain amps are designed to distort. They have far less clean headroom, so the preamp tubes compress and overdrive at lower volume levels.
Typical features of high-gain guitar amps:
- Preamp distorts at lower gain settings
- Gain knob controls amount of distortion
- Lower wattages like 15W to 30W
- Separte preamp and master volumes
- Popular with metal, hard rock, grunge guitarists
The classic Marshall JCM800 is a good example of a high-gain amp. Turning up the gain knob produces creamy tube overdrive even at low volumes, perfect for rock and metal.
How to Use Guitar Amp Gain
Now that you understand the basics of preamp gain, let’s go over some tips for using gain to achieve different guitar tones.
Clean Tones at High Volumes
For clean tones with plenty of volume, use lower gain settings on an amp designed for headroom. This allows volume with no distortion:
- Set gain low to maintain clean headroom when loud
- Turn up master volume to desired loudness
- Use EQ to shape tone brightness
This works well with low-gain amps like Fenders. The key is keeping gain low even when maxing the master volume.
High-Gain Distortion
High-gain amps specialize in distortion by overdriving the preamp. Here’s how to use gain for metal/rock tones:
- Increase gain until desired level of distortion
- Max preamp volume to overload tubes
- Lower master volume to manage loudness
- Use EQ to shape tone as needed
This technique really lets you control the amount of gain and distortion independent of final output volume. Perfect for classic rock and high-gain metal.
Edge of Breakup Overdrive
One cool sound is when the amp is just on the edge of distorting. You get tube warmth and compression but still retain some clean headroom and dynamics. Try this gain setting:
- Set gain so picking lightly is still clean
- Harder picking compresses signal and distorts
- Back off volume to control loudness
The goal is to ride that line between clean and dirty. Lower gain gives a cleaner sound with some transparency.
Finding the Sweet Spot
Gain, volume, and distortion are all connected but each affects the tone differently. Here are some tips for dialling in that perfect tone:
- Start with gain low and tone controls at 12 o’clock
- Increase gain until amp just starts to compress and break up
- Back down gain slightly until you reach the sweet spot
- Use volume controls to set loudness as desired
- Fine tune EQ settings to shape the sound
It takes some tweaking to find that magical tone we all seek. But understanding gain puts you in control of the three key factors: gain, volume, and distortion.
Conclusion
If you’ve ever been confused about gain on your guitar amp, hopefully this clears things up.
Here are the key points:
- Gain controls the level of signal entering the preamp
- Higher gain increases volume and drives the preamp tubes harder
- Too much gain causes distortion as tubes are overdriven
- Volume controls final output level through the power amp
- Low-gain amps focus on clean headroom, high-gain amps on distortion
- Use gain to find the edge of breakup and other sweet spots
So now you have a better understanding of gain and how it interacts with volume, distortion and headroom. Knowing how to use gain will help you dial in amazing tones.
Next time you’re tweaking your amp, think about where the gain is set. Lower gain for clean headroom and dynamic response. Higher gain for tube compression and distortion. Let your ears be the judge to find that perfect tone.