What does "presence" do?

[randelli]

I have a Fender Ultra Chorus and it has a "presence" control in the drive channel. I have turned the knob a few times but could not hear much of a difference in tone.

Does it affect the tone more with higher gain OD than a low gain setting?

A brief explaination of the function and ome suggested settings would be helpful.

Thanks!

[hbucker]

It's like a more focused treble knob. I use it with my treble to dial out harshness.

[slowhand0461]

Originally Posted by hbucker

It's like a more focused treble knob. I use it with my treble to dial out harshness.

+1

[bildozr]

I keep it about 8 and use my volume knob on my guitar to mess with the gain.
It's like an "Attack" or "Bite" knob.

[PMcG No.6]

I have it on my Hot Rod DeVille and don't notice a huge difference in tone either. Mine is at about 3 currently.

[Splattle101]

It's a high pass filter, like the treble control, but it passes higher frequencies. The presence control deals with frequencies you get in sibilance and cymbals, or in the hissing crackle of an over driven guitar amp.

Splat

[monroe]

In a tube amp, the presence control is not in the tone stack, it is in the NFB loop.
Changing the amount (or EQ) of the NFB signal varies the damping factor of the amp, thus effecting the perceived tone and feel of the amp.

[randelli]

OK so since this is a solid state amp, when I get the high-gain shhhhhhhhhhhhhhhh sound, I can roll the presence off to remove that. Kind of like a notch filter on a PA board.

[voxac30dude]

no because it will get really muddy with it off.

[toneguy86]

I think what the presence knob does really depends on the amp. On my Lonestar it affects the feel and stiffness of the attack. With the knob at lower levels you have a spongier, more compressed feel and a bit darker sound. At higher levels you have a brighter sound and a stiffer, more pick resistant feel. That may partly be due to how Mesa uses that control. I have played other amps with a presence control that didn't seem to have such a great effect on the sound.

Mark

[996ttcab]

Presence covers a mere half-octave of 4 kHz to 6 kHz, it is an often-used band of frequencies. This range makes most vocals and melody instruments sound closer and more distinct. Over-boosting causes a irritating and harsh sound. Equalization centers around 5 kHz."

Audio waves that are "out of phase" will cancel each other out. Negative feedback exploits this. Tube amps are hardly "linear" or "flat" when it comes to frequency response. Specifically, there is usually a 'bump' in the midrange. In many hi-fi circuits (and guitar amps starting with the fender brownface amps, since Leo was always looking for a more 'hi fi' sound) there will be a small amount of the output signal "fed back" into the audio path at an earlier point with polarity inverted so that it is out of phase with the main signal.

Since we know that two signals out-of-phase will cancel, this means that a little bit of the audio gets cancelled out. This works to "flatten" the frequency response, since the frequencies that are loudest in the fed-back signal get attenuated most in the overall output. The loudest bits of the fed-back signal are doing "the most cancelling," to put it another way.

If you add tone controls (like a simple capacitor treble-bleed off tone control as on your guitar) to the negative feedback circuit, you control how much treble gets fed back and "cancelled out." By turning the presence "up" we are actually 'darkening' the signal in the negative feedback loop, making it so that the treble frequencies are "less cancelled." This gives not just a brightness, but an overall liveliness in the top end that cannot be accomplished with a simple treble boost.

[toneguy86]

Originally Posted by 996ttcab

Presence covers a mere half-octave of 4 kHz to 6 kHz, it is an often-used band of frequencies. This range makes most vocals and melody instruments sound closer and more distinct. Over-boosting causes a irritating and harsh sound. Equalization centers around 5 kHz."

Audio waves that are "out of phase" will cancel each other out. Negative feedback exploits this. Tube amps are hardly "linear" or "flat" when it comes to frequency response. Specifically, there is usually a 'bump' in the midrange. In many hi-fi circuits (and guitar amps starting with the fender brownface amps, since Leo was always looking for a more 'hi fi' sound) there will be a small amount of the output signal "fed back" into the audio path at an earlier point with polarity inverted so that it is out of phase with the main signal.

Since we know that two signals out-of-phase will cancel, this means that a little bit of the audio gets cancelled out. This works to "flatten" the frequency response, since the frequencies that are loudest in the fed-back signal get attenuated most in the overall output. The loudest bits of the fed-back signal are doing "the most cancelling," to put it another way.

If you add tone controls (like a simple capacitor treble-bleed off tone control as on your guitar) to the negative feedback circuit, you control how much treble gets fed back and "cancelled out." By turning the presence "up" we are actually 'darkening' the signal in the negative feedback loop, making it so that the treble frequencies are "less cancelled." This gives not just a brightness, but an overall liveliness in the top end that cannot be accomplished with a simple treble boost.

Is this how all presence contols work?

Mark

[hbucker]

It really does depend on the amp. All eq's do for that matter. EQ and Presence are generally set for the amp, not universally.

[996ttcab]

Mark:

Generally, yes. Although people do tend to refer to presence as treble, people who I generally felt where in the know such as studio whizes, sound engineers and etc. have always told me that presence was a bit above treble in the frequency range. I have not recorded in a studio in years, but I believe my memory is correct.

hbucker:

One could say that each amp manufacturer sets bass, mid and treble controls on slightly different frequencies (again, I dunno), but I believe a true presence will always be the step above treble and in the 4k and up range. Simply adding another treble boost in the same frequency range as your treble control would not accomplish the objective of presence as stated above. But, yes, you are correct is a presence is a more focused treble in general terms.

[glp]

Monroe got it right! It is a variable control from the NFB circuit.

Which is not to say that 996ttcab didn't expand correctly on the subject.


www.recycledsound.net

[randelli]

I knew I could count on MLP'rs to know the answer to this!

Thanks

[ossie]

Maybe this will help, knowing what is going on inside an amp can help decide how best to use it. WARNING what comes next is brief, boring, and not really comprehensive. I mean you could literaly write a PHD thesis on feedback, and bore the hell out of everyone, esp me.

OK, NFB (negative feedback) is added to an amp design to increase linearity and produce a cleaner signal. It works by phase cancellation... one signal being combined with another out of phase signal. When these two signals combine they cancell each other out. When a portion of an amps whole signal is fed back to a previous stage of the same amp the whole signal is attenuated, This reduces distortion, and volume. With enough NFB you could make an amp go silent. When you selectively decouple any frequency from this loop, disconnect it, you precieve a boost in that freq range (even though it is not a boost, just a lack of attenuation). Presence controls work this way.

I think you could say that in general that "presence" features give contoll over the higher frequencies. I think most players associate the feature with the presence control on old marshall amps. Some prefer to think of them as high pass filters but these circuits are in in fact low pass filters (hold on) located in the NFB loop of the poweramp.

The procesess is real simple... A small amount of signal is taken directly from the secondary of the output transformer(speaker out) and fed through an r/c network to form a filter, in this case a low pass filter.. The output of this filter is combined with the primary signal, usually at the phase inverter (allthough the majors had it fed all the way back to the cathode follower of the tone stack, really you can feed it anywhere you want to but it must be out of phase to work otherwise you will have postive feedback and armageddon). Now, because this filtered signal is out of phase with your primary signal the primary signal is attenuated at all frequencies that can pass by the filter. Now if the filter is set to pass all frqs below say 2khz all freqs above 2kz become stronger in relation to the lower freqs . The freqs above 2k have been attentuated at the low pass filter and dont pass on with the same strength as the lower feqs and thefore do not have a strong cancelling effect .

Now a company can design the resistor/capacitor network forming the filter to raise or lower the cut off of the filter and change what freq's are attenuated, and how much, so not all pres controls work the same way. You might even consider tailoring that control to your needs.

So in conclusion, (thank god) your pres controll decouples the freqs as set by the r/c network (the filter) from the NFB - so they are no longer being attenuated and as a result they become pronounced.. As a side not the "resonance" control is just the opposite of the pres, it decouples the lower freqs from the feedback loop resulting in a loose big bottom.

Hope you can make sense of this drivel..

Ossie

[st.bede]

Originally Posted by 996ttcab

Generally, yes. Although people do tend to refer to presence as treble, people who I generally felt where in the know such as studio whizes, sound engineers and etc. have always told me that presence was a bit above treble in the frequency range. I have not recorded in a studio in years, but I believe my memory is correct.

to my knowledge you got it 100% right...and it was very well put...when I say this question I was dreading to write a responce...yours was way more elegent then I could of ever done...

the next thing, I would point out: is that a lot of people belive that the reason for a vox having it's chime (or it's own tonal charteritics) has to do with it being a class A amp, that is not true...it has (in a large amount) to do with the negitive feedback (as describe above)....(now, an hiwatt is a class A amp....)

of course, it has been a long time since I read this stuff, so it is based off my memory...so if I am missing something, please chime in and tell me)

(and, sometimes people will speak about the range in which presence lives as air or an hi-fi type sound.....the "smile" curve adds a little "air" or "presence".....if there is too much it sounds harsh or strident and is fatiguing)

[monroe]

Originally Posted by st.bede

(now, an hiwatt is a class A amp....)

Class A

[randelli]

Originally Posted by ossie

As a side not the "resonance" control is just the opposite of the pres, it decouples the lower freqs from the feedback loop resulting in a loose big bottom.

SOMEBODY has been messing with my "resonance" control! Or, perhaps, I'm just getting older.

[ossie]

Originally Posted by randelli

SOMEBODY has been messing with my "resonance" control! Or, perhaps, I'm just getting older.

I set 'em up and you knock 'em down.

[diceman]

Great info in this thread. I have a "presence" knob on my Laney GH50L - I knew what it did to my sound based on my experience using it, but had no idea what it was actually doing.

You guys really helped make sense of it all!

[mojofilter]

I'll give it to you simple,Presence when turned all the way up will put the sound right your face along with some high[treble] frequencies! ALL amps vary to a different degree.many amps do not have presene controls also.hope this helps buddy!

[jo07]

it shape the sound

[Blind Willie]

From an article I have on amplifier EQ.

10-14kHz: This range is another two-edged sword. It's the "presence" range on most amps, and used correctly, can take the blanket off of an otherwise muffled sounding guitar. However, it's also the range most responsible for sibiliance...that nasty "sssss" sound that plagues vocal microphones. Adjustments in this range can also sometimes be sneaky in that it's easy not to notice the difference in tone an adjustment here has made, often resulting in the player making larger and larger adjustments. However, walking away from the project and coming back to it later can often reveal dramatic and harsh effects on tone that large adjustments can produce. Keep it subtle.

[Stowburst]

Originally Posted by mojofilter

I'll give it to you simple,Presence when turned all the way up will put the sound right your face along with some high[treble] frequencies!

My amp is so raw that I dont use the precence.. its just too brutal and sharp