The Presence Knob, Demystified

October 06, 2016 8 Comments

Many of Carvin Audio’s guitar amplifiers come equipped with a knob labeled Presence (such as Carvin Audio’s V3M, Legacy, and Belair, to name a few). Though the exact technical details of this mysterious knob may vary, its overall purpose generally remains the same- to add edge and brightness to your guitar tone and serve as an additional tone shaping tool. 

 

Presence Knob History

Most early single channel guitar amplifiers usually had this knob in the power amp section connected to the feedback of the amplifier. The Belair and Nomad Carvin Audio amplifiers use this location. The result of this location changes the high frequency roll off of the amplifier. This is different from a treble control that is located in the preamp EQ (equalization) section called a shelving filter, where it boosts or cuts the sound around a center point. At the center point, the treble knob is neutral, and tone is passed through unchanged. A presence knob only rolls off or cuts the high frequencies. It also changes its frequency of roll-off as it is turned up and down. On later multi-channel amplifiers the presence knob moved to the preamp section, usually located around the channel’s volume where it could be on each channel. The result was similar using a locally located high frequency roll off filter. Note the thinking is the presence knob is boosting frequencies like the other knobs, but it is actually in the circuit backwards and it is just cutting less. The center position is still cutting, but it is usually at the center position where you will achieve the amp designer’s intended sound.

 

Your Tone With the Presence Knob

When used in conjunction with the rest of the EQ controls, the presence knob can drastically change your guitar sound. This is especially true when used with the treble knob. The roll-off of the presence changes the treble knob to a peaking filter, where it boosts lower treble tones with a narrower peak. It will enhance the mids and bass also when turned down, because they will sound much louder. On the V3, V3M and Legacy the presence control adds high frequency content in the 5kHz to 10kHz range when turned up. This is a slightly higher range than where the treble control starts adjusting, making it especially useful for further fine tuning your tone. For a warmer sound, turn the presence down. Turn it up for added bite and clarity. You may want to adjust the treble again to fine tune further.

While the presence control naturally lends itself to crunchy rhythm guitar playing and searing leads when used in conjunction with a thick overdrive, it also is right at home with a clean tone. The Belair’s presence control, called the Acoustic Presence control, is slightly different. As mentioned it is located in the amplifier section, but only works with the clean channel. The point here was to let you adjust it for your clean tones and not affect the soak channel. The Belair’s Acoustic Presence control adjusts frequencies within 8kHz-20Hkz range. When applied to the clean channel, it adds a subtle shimmer to your guitar’s high frequencies, which is perfect for ringing out chiming fat chords.

Just like with any other of your amplifier’s controls, it definitely pays to be judicious with your adjustments. While turning up the presence control can be helpful and add filling character to your guitar tone, too much of it may clutter up the overall mix with the band. The “sizzle” from a drum kit’s snare drum or cymbals, a singer’s voice, and overtones from a piano also live in the range of 5kHz and above. In instances like these, turning down the presence control- rather than turning it up- may be the ticket to a guitar sound that sits nicely in the mix. Think of this knob as an additional tool to find the sweet spot in your tone.

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