What every knob on a guitar amp does
Gain sets how hard the preamp is driven and therefore how much distortion the amp makes. Volume sets how loud that is. On an amp with both a volume and a master volume, the first sets preamp level and the second sets how hard the power section works, which is a different kind of distortion with a different feel.
Presence and resonance sit after the tone stack and act on the power amp, so they behave differently from bass, middle and treble.
Gain, drive, preamp volume
All three names describe the same job: how hard the signal is pushed into the preamp's distortion stages. More gain means more saturation, more compression and more sustain, and less clarity between the notes in a chord.
Gain also interacts with your pickups. A high-output humbucker reaches a given amount of saturation at a lower gain setting than a single coil does, which is why the same number sounds different on two guitars through the same amp.
Volume and master volume
On a single-volume amp, the volume control does both jobs: it makes the amp louder and, past a point, drives the power section into distortion. This is why old amps only sound like the records at volumes that are impractical indoors.
A master volume splits the two. The first control decides how much preamp distortion you get, and the master decides how loud that is. Power-section distortion is looser and more responsive than preamp distortion, and getting it means running the master high and the preamp lower, which is the opposite of what most players do.
Bass, middle, treble
These form the tone stack, and on most amps they are interactive rather than independent: moving the bass control changes what the middle control does, because the circuit is a single passive network rather than three separate filters.
That interaction is why one control at a time is the only way to learn an amp. It is also why two amps with identical numbers on the panel do not sound the same. The tone stack sits at a different point in the circuit and is tuned around different frequencies.
Presence and resonance
Presence works above the treble range and, on most valve amps, does so by reducing negative feedback in the power section rather than by filtering the signal. In practice it adds bite and air, and it is the control that decides whether a distorted tone cuts through or sits behind everything else.
Resonance, sometimes called depth, is the same idea at the other end: it controls the low-frequency behaviour of the power section and the speaker together. Turning it up adds thump rather than the general weight the bass control adds.
Both act after the tone stack, so they can rescue a tone that the EQ alone could not.
Channel and voicing switches
A channel switch usually swaps between different preamp gain structures, not just different amounts of the same thing. Setting a clean channel's controls and expecting them to carry over to the lead channel does not work; each channel is dialled in separately.
On modelling amps, the voicing or model selector sets the ceiling that all the other controls work inside. Picking it is the first step of dialling in a tone, not a garnish at the end.
Common questions
What is the difference between gain and volume on a guitar amp?
Gain sets how hard the preamp is driven, which controls how much distortion the amp makes. Volume sets how loud the result is. On an amp with a master volume, the master controls how hard the power section works, which produces a looser, more responsive distortion than the preamp does.
What does the presence knob do?
Presence adds content above the treble range and, on most valve amps, works by reducing negative feedback in the power section rather than by filtering the signal. It adds bite and air, and it is usually what decides whether a distorted tone cuts through a band or sits behind it.
What does the resonance or depth control do?
Resonance controls the low-frequency behaviour of the power section and speaker together, adding thump and physical push rather than the broad weight the bass control adds. Like presence, it acts after the tone stack, so it can fix a low end the EQ could not.
Settings for your own amp
This guide covers what is true of every rig. For a specific song on a specific amp, Tonelify reads the documented chain behind the recording and returns gain, bass, middle, treble and presence values for the controls your amp actually has. Free for 7 days, no charge until the trial ends.
Keep reading
- How to EQ a guitar ampSet the gain first, then cut before you boost, and move one control at a time. A repeatable method for EQing any guitar amp, and what each band actually does.
- How pickups change your amp settingsHumbuckers hit the amp harder and darker, single coils lighter and brighter. What to change on the amp when you switch guitars, and why copied settings often fail.
- How to get a metal tone on any ampTight low end, controlled gain, mids you can hear and a gate. How to get a usable metal tone out of a practice amp, a modelling combo or a valve head.