Out of all the controls on a guitar amp, the presence knob is the one that causes the most confusion. In this article I’ll be explaining exactly how a presence control works, how it affects the tone, and why it’s NOT the same as a treble control.
Looking for a quick answer? Here’s a brief definition…
The presence control on a guitar amplifier sits in the power-amp stage and is used to boost the high-end frequencies resulting in a brighter, livelier and more raspy sound when using distortion.
Basic Function of the Presence Control
In a basic sense, the presence control on a guitar amplifier is used to adjust the overall treble and upper-mid range frequency response.
These frequencies shape how bright and crisp the tone is. Having more presence, results in a brighter and more lively sounding tone, whilst reducing the presence is useful if the tone sounds too harsh.
With this basic definition, the overall function of the presence and treble controls on an amp sound quite similar. However, these controls work very differently to one another. To understand this, we need to go into more depth on how an amp actually work, and hence how the presence control functions.
How Does the Presence Control Work?
Before we address the presence control directly, we need to go back a little bit and talk about the pre-amp and power-amp stages of an electric guitar amplifier.
- The pickups in the electric guitar produce a weak signal called the “instrument level” signal
- The pre-amp stage of the amp raises this signal from instrument level to line level
- The power-amp stage raises the line level signal to speaker level signal
The pre-amp stage is largely responsible for shaping the tone, whereas the power amp stage is mostly responsible for increasing the volume.
The presence control sits in the power-amp stage of the amplifier so it is able to boost the upper-mids and treble frequencies. For this reason the presence control is also commonly referred to as a “high-frequency shelving boost”.
It’s important to recognise that the presence control boosts, rather than cuts or limits these frequencies as these two methods of adjusting the high-end frequency response have quite different impacts on the tone (more on this later).
Presence vs Treble Control
The presence and treble controls are both responsible for affecting the high-end frequencies and controlling how bright and defined the tone is, however they work quite differently to one another.
On an amp you’ll typically find 3 traditional EQ controls: bass, mids and treble.
The bass, mids, treble and gain controls on an amp are part of the pre-amp section. Hence, they shape the tone when it is being raised from instrument to line level.
Whereas, the presence control is part of the power-amp section of the amplifier so shapes the tone when it is raised from line to speaker level.
This is an important distinction to make as it affects how these controls are actually able to alter the overall tone of your electric guitar.
EQ Controls (Pre-Amp Stage)
The EQ (bass, mids and treble) controls work in a subtractive way because they sit in the pre-amp stage. This means that they cannot increase or boost these frequencies, but they can decrease them. Essentially, they control how much of the potential frequency actually goes through to the power-amp stage.
Presence Control (Power-Amp Stage)
The presence control works in an additive way because it sits in the power-amp stage. This means the presence control cannot reduce the upper-mids or treble frequencies, but it can increase them. In other works, the presence controls boosts these high-end frequencies.
To summarise…
Both the presence and treble controls affect the high-end frequencies so can be used to adjust how bright and defined the tone is. However, the presence control sits in the power-amp stage so can boost the high-end frequencies, whereas the treble control sits in the pre-amp stage where it can limit them.
How Does This Affect the Tone?
Okay so now we know that the treble and presence controls sit in different stages of the amp and work very differently to one another, we can now address how they affect the tone too.
The treble control is fairly straightforward. Having it on a high setting will result in more high-end frequencies being amplified, resulting in a brighter and crisper tone. Decreasing the treble control will limit those high-end frequencies and cause the tone to sound more mellow and less defined.
The presence control also will cause the tone to be brighter and crisper when on a high setting, similarly to the treble control however it also has some more interesting effects, depending on whether the tone is clean or distorted.
Clean Tone Effect
When using clean amp settings where the amp is not pushed to the point of overdrive, the effect of increasing or decreasing on the overall tone of the amp is similar when adjusting the treble and presence control.
For maximum brightness, you’d want to increase the treble control (so the frequencies are not being limited) and also increase the presence control (so the frequencies are being boosted as well).
The difference is that the presence control is capable of creating a treble peak which causes the tone to have more brightness and cut.
Distorted Tone Effect
The interesting effects of the presence control become apparent when the amp is pushed into overdrive.
When using distorted/ overdriven amp settings, the presence control will also affect the distortion of those higher upper-mid range and treble frequencies because it sits in the power-amp stage and boosts the frequencies.
This is what causes the tone to sound more raspy and unpredictable, giving it that liveliness that you’d associate with a high presence setting. Since the presence control only adjusts the high-end frequencies, the result is that these frequencies are more distorted compared to the lower-end frequencies.
This creates an interesting effect because it means you can take a high gain sound from dark to biting just using that presence control.
The treble control does not have this effect as it is incapable of controlling the distortion of those high-end frequencies as it sits in the pre-amp stage of the amplifier where it can only limit the frequencies.
To really understand how the presence control affects tone, it’s a good idea to listen to a demo. Here’s a YouTube video which demonstrates the difference between a high and low presence setting.
Looking to get the most from your guitar amp? Check out my complete guide to electric guitar amp settings and controls for everything you need to know.
Which Amps Have a Presence Control?
Fender first introduced presence controls on some of their guitar amps in the ’50s but many other brands use them too including Marshall and Blackstar. Typically, the presence control is seen on more expensive tube amps, but it can be found on less expensive solid state amplifiers too.
Here’s a list of popular electric guitar amps which have a presence control:
- Marshall Origin
- Marshall DSL
- Marshall Studio Classic and Vintage
- Marshall JMV
- Marshall JTM
- Marshall Silver Jubilee
- Fender Hot Rod Deluxe
- Fender Blues Deluxe
- Fender ’59 Bassman
- Blackstar Silverline Deluxe
- Blackstar HT Venue Stage
- Blackstar Silverline Deluxe
- Boss Nextone
- Boss Waza
- Peavey Vypyr Pro
- Peavey 6505
- Peavey Inective.120
- Vox MVX