Is Mesa's presence control different than.. 'others?

[mixsit]

" The PRESENCE control is a high frequency attentuator that is placed at the end of each channels pre-amp stage and affects frequencies higher than.. (etc.)"

Is this otherwise done as a neg feedback loop in the output tubes? (or 'around- not sure of the terminology

 

[Greg_L]

" The PRESENCE control is a high frequency attentuator that is placed at the end of each channels pre-amp stage and affects frequencies higher than.. (etc.)"

Is this otherwise done as a neg feedback loop in the output tubes? (or 'around- not sure of the terminology

It's my loose general understanding that some Mesa models do not use any negative feedback. Like the Dual Rec, Roadster, stuff like that. That's partly why they have such gigantic bottom end. Mesa's presence control is basically just another EQ knob, a filter, whereas on most other amps the presence control does interact with the negative feedback and it's effect is dependent on master volume.

I could have that all wrong though, or backwards. I've just heard that some Mesas have a fake presence control and it has something to do with their lack of negative feedback.

 

[mixsit]

Thanks, yeah that's kind of what I was wondering. I never paid all that much attention as to what or how stuff goes on in amps, butI've been trying to get some insights as to how this stuff works -the tone stacks', inter stage gains etc.
One thing that's caught my eye', is I basically (almost always) hate fizz on top. And it occured that as I'm currently running that control' at 'full cut' and still hearing it.. if it were in the output tube loop.. I might be liking the tones better?

BTW, i've been comparing the 'Rectifier, and a few others manuals to the Lonestars (I have the lower power 'special) just to see, and they all pretty much say similar things with regard to this, and the tone controls etc.

 

[Tadpui]

I recently revisited the excellent owner's manual for my Lonestar Special and read that same bit about the presence control. It's such a dark-voiced amp, I was looking for ways to brighten it up without it getting fizzy. I didn't have much success. I did get some better results after realizing that I should dial the bass way down when I have the gain control turned up. That did help the dark voicing a bit...I had just assumed it was so bassy because of my crappy room. 12:00 didn't seem out of the ordinary for the bass setting, but it turns out that was way too high when the gain was up past 2:00.

But yeah, the presence is basically a super-treble on the Lonestar that controls frequencies higher than what the treble knob controls. The tone stack on this thing is like a freaking combination lock. Turn one knob and it affects how all of the subsequent knobs behave. I usually have the presence knob either all the way down, although recently I've started notching it up to about 8:00 or 9:00, in an attempt to help the amp shine through a mix more clearly.

 

[Greg_L]

Thanks, yeah that's kind of what I was wondering. I never paid all that much attention as to what or how stuff goes on in amps, butI've been trying to get some insights as to how this stuff works -the tone stacks', inter stage gains etc.
One thing that's caught my eye', is I basically (almost always) hate fizz on top. And it occured that as I'm currently running that control' at 'full cut' and still hearing it.. if it were in the output tube loop.. I might be liking the tones better?

BTW, i've been comparing the 'Rectifier, and a few others manuals to the Lonestars (I have the lower power 'special) just to see, and they all pretty much say similar things with regard to this, and the tone controls etc.

Try alternating the presence and treble knob. Cut the treble off and use the presence as your "highs". See what that does.

I recently revisited the excellent owner's manual for my Lonestar Special and read that same bit about the presence control. It's such a dark-voiced amp, I was looking for ways to brighten it up without it getting fizzy. I didn't have much success. I did get some better results after realizing that I should dial the bass way down when I have the gain control turned up. That did help the dark voicing a bit...I had just assumed it was so bassy because of my crappy room. 12:00 didn't seem out of the ordinary for the bass setting, but it turns out that was way too high when the gain was up past 2:00.

But yeah, the presence is basically a super-treble on the Lonestar that controls frequencies higher than what the treble knob controls. The tone stack on this thing is like a freaking combination lock. Turn one knob and it affects how all of the subsequent knobs behave. I usually have the presence knob either all the way down, although recently I've started notching it up to about 8:00 or 9:00, in an attempt to help the amp shine through a mix more clearly.

On my Marshall JCM 800 2203 and 2204, they both have the least negative feedback of the entire Marshall lineup. They can start to get bottom heavy as the volume goes up. The louder you turn them up, the less "bass" setting you actually need.

 

[Tadpui]

On my Marshall JCM 800 2203 and 2204, they both have the least negative feedback of the entire Marshall lineup. They can start to get bottom heavy as the volume goes up. The louder you turn them up, the less "bass" setting you actually need.

And I should have known that. That's kind of a rule of thumb with amplifiers...I've had a few hi-fi systems that had the "groove" or "max bass" button that's intended to enhance the bass when listening at low levels. But above a certain volume, they aren't needed because the amplifier/speakers produce plenty of bass. It seems like the same principal at work here.

 

[Greg_L]

And I should have known that. That's kind of a rule of thumb with amplifiers...I've had a few hi-fi systems that had the "groove" or "max bass" button that's intended to enhance the bass when listening at low levels. But above a certain volume, they aren't needed because the amplifier/speakers produce plenty of bass. It seems like the same principal at work here.

With "loose" amps, yes that seems to be the case. Mesas, Vox, and the two Marshalls I mentioned are pretty loose with a less restrictive negative feedback loop. Vox and Marshall counters this with top boosts and bright caps. Mesas just stay fat and blubbery. My JVM and Plexi are "tight" though with a lot of negative feedback and they stay tight and articulate pretty much no matter what the volume does. The JVM especially. Modern Marshalls are very tight amps with a lot of negative feedback to preserve that tight Marshall midrange at higher gain settings. They can sound stiff though at lower volumes, so Marshall has recently started putting in a "resonance" control which acts like a presence for the bottom end. Works great for lower volumes. Not necessary when the volume goes up.

 

[mixsit]

Mesas, Vox, and the two Marshalls I mentioned are pretty loose with a less restrictive negative feedback loop. Vox and Marshall counters this with top boosts and bright caps. Mesas just stay fat and blubbery. My JVM and Plexi are "tight" though with a lot of negative feedback and they stay tight and articulate pretty much no matter what the volume does. ..

Greg, are you referring to neg. feedback for their presence controls, or more the fixed types in part of the amp's designs?

I might add that loudness contour on hifi's is coming from a bit of a different direction- i.e, tone shaping to compensate for our ears at low volume. Needing to cutting lows as the distortion goes up, while Fletcher Munson's in play, I'd bet part of it is more lows' can work and you can get away with it more lower (cleaner') volumes, but starts to make a mess of it at higher gains.

 

[Greg_L]

Greg, are you referring to neg. feedback for their presence controls, or more the fixed types in part of the amp's designs?

I only know about a few Marshalls, and not even too much about them, but I know that the negative feedback is fixed via resistor on the circuit board. I don't know the technical specifics, but I know that once that little resistor can't control the negative feedback anymore, the presence control begins to lose it's effectiveness. If I remember correctly, the negative feedback wire on my 2204 comes off of one of the lugs of the presence pot. People swap out resistors or taps on the output tranny to achieve different neg feedback values which will tighten or soften the power section. I modded a pot into my JVM to "loosen" it up some and act more like a 2203/2204 when I want it to. I can have the amp at it's low-resistance-high-neg-feedback stock value, or twist the pot until there's no negative feedback whatsoever. But at some point on every fixed-value amp eventually the whole system breaks down and the power tubes go wide-open full power. This is usually at a volume that will knock down walls. You can hear the amps come alive. The phase inverter plays a role in this too. That's part of the "cranked Marshall" magic. This just my very rudimentary layman's understanding of it. I could have it all wrong, so don't take my word as definitive.

 

[mixsit]

Cool, and thanks. I don't need to get deep into it so just getting the gist of it helps.

 

[freddycash]

The whole eq is different than normal amps. The presence is like extra treble. I can give you my settings if you want. A clean boost in front will tighten up the low end too. And I use a boss ns2 to keep the amp quiet