Mesa D800+

[Doufuss]

In the semi parametric section of this amp's tone controls, you have low mid frequency control from 150 to 1800 Hz and in the hi mid you have 300 to 5000 Hz. What is the frequency of each control at noon? And establishing this, would it be reasonable to interpolate frequency centers based on averaging? Or is it logarithmic? Secondarily, what is the Q of each of these controls?

Thanks in advance.

 

[600 Ohms]

Hang on... I’ve done the work. I need to dig it up.

The Q is quite wide. Andy should chime in, but they sound wider than 1.0 to me. More like 0.7 or 0.8. Curious to know the real number.

You can't really interpolate the other positions, and your pots may vary from mine in their tolerances. The pics below are from my own unit, and I found them by sending a sine wave at those frequencies and finding the peak by sweeping.

 

[600 Ohms]

 

[600 Ohms]

I decorated my faceplate with commonly needed frequencies for quick reference.

Note how close 300 and 500 are.

 

[agedhorse]

IIRC, the Q is about 1.4

 

[600 Ohms]

IIRC, the Q is about 1.4

One octave, in other words. I’m shocked!! It sounds even more gentle.

 

[agedhorse]

1.4 is pretty wide actually, one octave bandwidth.

 

[600 Ohms]

I measured a Q factor of 1.6:

707 - 382 = 325 (Bandwidth)

Audibly it feels broader than 1.6. Interesting! The good news is you can't make it sound bad. One of the better tone stacks of the current era.

 

[Doufuss]

Hang on... I’ve done the work. I need to dig it up.

The Q is quite wide. Andy should chime in, but they sound wider than 1.0 to me. More like 0.7 or 0.8. Curious to know the real number.

You can't really interpolate the other positions, and your pots may vary from mine in their tolerances. The pics below are from my own unit, and I found them by sending a sine wave at those frequencies and finding the peak by sweeping.

Nice. What a great idea. This is going to be a great help.

 

[cyberhawk]

600 Ohms,
You didn't happen to scope the freqs of the voicing control?
I love my 800+!

 

[600 Ohms]

600 Ohms,
You didn't happen to scope the freqs of the voicing control?
I love my 800+!

View attachment 4109753

Voicing is what got me scoping this thing in the first place, cause it's a one-knob wonder and I wanted to know what it was doing, and what it's doing is actually pretty sophisticated. The purple line is the flat setting and each grade is the knob at the "clock-face on the hour", starting with 8:00, know what I mean? You can also see the 30Hz HPF in effect at all times. Voicing's dip is centered around 650Hz (my chiclet is a few pixels under by the looks of it).

 

[cyberhawk]

Thanks! That's fantastic.

 

[Doufuss]

This is cool. Thanks @600 Ohms.

Here's a thing that amp manufacturers could add to their manuals that might help the user.

From Markbass

 

[600 Ohms]

This is cool. Thanks @600 Ohms.

Here's a thing that amp manufacturers could add to their manuals that might help the user.

From Markbass

View attachment 4109862

I agree. It's nice to have a visual, even though you're using your ears to dial it in, because I'd rather learn something from the correlation, but most people are happy to turn knobs till it sounds good. I've always been the take-it-apart guy.

 

[agedhorse]

I made the mistake on a product years ago of including graphical data. I had so many players proclaim that it couldn't possibly sound good because "everybody knows..."(fill in the myth of the day) WITHOUT EVER TRYING THE AMP that it cured me of providing graphs.

The problem isn't with folks that (really) understand the information that the graphs provide, but the vast majority who haven't the slightest clue yet proclaim to be experts. They provided the disincentive, and it was a crystal clear lesson in human nature.

Yes, there are 5 simultaneous things happening with the voicing control, some absolute changes and some relative changes.

 

[600 Ohms]

I made the mistake on a product years ago of including graphical data. I had so many players proclaim that it couldn't possibly sound good because "everybody knows..."(fill in the myth of the day) WITHOUT EVER TRYING THE AMP that it cured me of providing graphs.

The problem isn't with folks that (really) understand the information that the graphs provide, but the vast majority who haven't the slightest clue yet proclaim to be experts. They provided the disincentive, and it was a crystal clear lesson in human nature.

Yes, there are 5 simultaneous things happening with the voicing control, some absolute changes and some relative changes.

Yeah, I can understand why that would put you off! Judging a book by its cover is one of the failures of human nature. The only reason I like to measure is to increase my understanding after I've got to grips with what it sounds like. I suppose I'm a Kelvinist at heart (and in the minority).

 

[agedhorse]

Yeah, I can understand why that would put you off! Judging a book by its cover is one of the failures of human nature. The only reason I like to measure is to increase my understanding after I've got to grips with what it sounds like. I suppose I'm a Kelvinist at heart (and in the minority).

Agreed, and when measurements don't match perception, I investigate to see if the measurements are off or my perception is off. I see many folks take measurements as gospel yet fail to recognize when the measurements are simply wrong!

 

[600 Ohms]

Agreed, and when measurements don't match perception, I investigate to see if the measurements are off or my perception is off. I see many folks take measurements as gospel yet fail to recognize when the measurements are simply wrong!

And as you say, my perception was clearly off in my initial guess. This is why I like to know.