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[Hot Rats]

Here is the description form the version of the manual I have (although it might have been an earlier version from when we were testing the prototype):
PASSIVE MID CONTROL: This eq control is an integral part of the amplifier’s voicing circuit and is responsible for the amount of midrange frequency content present in the signal, relative to the rest of the spectrum. Midrange is primarily responsible for voicing and articulation character of the instrument. This is a passive control with cut only, the amount of cut roughly proportional to the counter-clockwise rotation of the control. Due to the specific way this filter is implemented by the use of make-up gain, most users will find that their flat or neutral tone will be from the 10:00 to 2:00 position, and this might give the appearance of boost as the control is rotated farther clockwise. This filter’s Q (width) symmetry and response is quite different from the parametric mid section, which is typically used more for precise tuning of the amp’s response.

EDIT: As best I recall from discussions during the manual review and beta testing, Andy had had not made too many tweaks to the mid control circuitry as he believed most folks liked how it worked on the original WA. I think he mostly just made sure it was well integrated into the new circuit design. This makes me think that the that the original WA employed a very similar mid circuit, but that it may not have been as thoroughly explained in the manual. Andy and Mesa wanted to be sure the WD-800 manual helped users get the most out of the head by providing a deeper understanding of the design features (especially the unique ones) than even their usual manuals do (which are quite comprehensive IME).

Yep, that's a good, thorough explanation and pretty much how I've come to understand it through experience. I'm sure it's a misprint in the early manuals as the word boost only doesn't make much sense within the paragraph. I was pointing out the confusion part of it.

 

[TomB]

Here is the description form the version of the manual I have (although it might have been an earlier version from when we were testing the prototype):
PASSIVE MID CONTROL: This eq control is an integral part of the amplifier’s voicing circuit and is responsible for the amount of midrange frequency content present in the signal, relative to the rest of the spectrum. Midrange is primarily responsible for voicing and articulation character of the instrument. This is a passive control with cut only, the amount of cut roughly proportional to the counter-clockwise rotation of the control. Due to the specific way this filter is implemented by the use of make-up gain, most users will find that their flat or neutral tone will be from the 10:00 to 2:00 position, and this might give the appearance of boost as the control is rotated farther clockwise. This filter’s Q (width) symmetry and response is quite different from the parametric mid section, which is typically used more for precise tuning of the amp’s response.

EDIT: As best I recall from discussions during the manual review and beta testing, Andy had had not made too many tweaks to the mid control circuitry as he believed most folks liked how it worked on the original WA. I think he mostly just made sure it was well integrated into the new circuit design. This makes me think that the that the original WA employed a very similar mid circuit, but that it may not have been as thoroughly explained in the manual. Andy and Mesa wanted to be sure the WD-800 manual helped users get the most out of the head by providing a deeper understanding of the design features (especially the unique ones) than even their usual manuals do (which are quite comprehensive IME).

So maybe I'm a little dense, but does "cut-only" imply that "flat" is achieved with the mid control dimed? Is "flat" even an issue with this amp? It's been a while since I played a Walkabout, sorry.

 

[agedhorse]

Please read the description of the mod control that Al posted above. That's how the control works, there are multi-dimensional aspects to how this control works. It's similar in the original WA, but the WD includes some additional fine tuning as requested by many players to be even more useful.

 

[Al Kraft]

So maybe I'm a little dense, but does "cut-only" imply that "flat" is achieved with the mid control dimed? Is "flat" even an issue with this amp? It's been a while since I played a Walkabout, sorry.

Agedhorse will have to save the day here as I suspect the 100% technically correct answer may tread into some proprietary design aspects. To me, the simple answer is that the fundamental filter design is one where you would have full mids at full clockwise and and a continuing scoop (or attenuation) as you rotate CCW from the full position (very much the classic passive mid). However, there is an added make-up gain circuit that actually boosts the mid signal in a way that this ordinarily passive (cut-only) control actually has its flat position around 10-12 o'clock. There is a musically subtle difference between this and a totally active control where you have have no boost at noon, boost past noon and cut below. Andy will need to explain the specifics and why it makes such a difference to the player while not compromising any trade secrets...I'm already a bit out of my comfort zone and technical depth.

 

[nostatic]

"Flat" is a term of art meaning the frequency curve is...flat. "Cut only" is also a term of art meaning the control only attenuates frequencies. The two don't necessarily mean that dimed is neutral but it can, depends on how the tone stack is done. "Neutral" is another term that some use as a synonym for "flat".

I may have misspoke about flat being dimed, but given @agedhorse mentioning somewhere between 10-2 being neutral, that leads me to believe that there may not be much "flat" going on due to other interactions. For my purposes, I just go where I like the sound which is around 3:00.

 

[TomB]

Agedhorse will have to save the day here as I suspect the 100% technically correct answer may tread into some proprietary design aspects. To me, the simple answer is that the fundamental filter design is one where you would have full mids at full clockwise and and a continuing scoop (or attenuation) as you rotate CCW from the full position (very much the classic passive mid). However, there is an added make-up gain circuit that actually boosts the mid signal in a way that this ordinarily passive (cut-only) control actually has its flat position around 10-12 o'clock. There is a musically subtle difference between this and a totally active control where you have have no boost at noon, boost past noon and cut below. Andy will need to explain the specifics and why it makes such a difference to the player while not compromising any trade secrets...I'm already a bit out of my comfort zone and technical depth.

Ah, great explanation! ...assuming you're right . Thank you & Happy Holidays all!

 

[Doug Parent]

Anyone try the Subway 212 yet?

 

[Hot Rats]

Crud. I apologize for interjecting the original Walkabout mid control into this thread. I see now that it's about the new Subway amplifiers. Wrong thread......Merry Christmas everyone.

 

[Al Kraft]

Ah, great explanation! ...assuming you're right . Thank you & Happy Holidays all!

I'm pretty sure if Andy was giving our posts grades I would be getting at worst a B+ on this one. I know I got the concept right, but may have lost points on my technical nuance description...those Mesa guys have high standards and Andy is a particularly tough grader when it comes to technical accuracy and precise answers!

 

[/\/\3phist0]

Fwiw the Sonic difference the the passive mid makes is a fairly wide Q, sounds to me to be centered at about 800hz with a drifting center Q, when moving past @2:00 begins to raise the frequencies at and above slightly more than the frequencies below the center.
And when cutting, the bell curve seems to be narrower, and the dip, is moving bias a little lower in the frequencies..

 

[Acoustic356]

WD Serial Number 87... I think it's cool that they are signing them!

 

[nostatic]

drifting center Q

I hear they did a Christmas album this year...

 

[Al Kraft]

Fwiw the Sonic difference the the passive mid makes is a fairly wide Q, sounds to me to be centered at about 800hz with a drifting center Q, when moving past @2:00 begins to raise the frequencies at and above slightly more than the frequencies below the center.
And when cutting, the bell curve seems to be narrower, and the dip, is moving bias a little lower in the frequencies..

...and this could easily be the place I lost the "musical subtlety description points" in my answer.

 

[TomB]

Fwiw the Sonic difference the the passive mid makes is a fairly wide Q, sounds to me to be centered at about 800hz with a drifting center Q, when moving past @2:00 begins to raise the frequencies at and above slightly more than the frequencies below the center.
And when cutting, the bell curve seems to be narrower, and the dip, is moving bias a little lower in the frequencies..

Fascinating stuff, and fun to play with, I'm sure. It sounds like a very cool control. Thanks for your indulgence and explanations.

 

[agedhorse]

There are multiple things going on with the mid control, that's what makes it more useable. We did improve the smoothness of operation of the filter with control rotation.

 

[nostatic]

I will reiterate my first impression - there is a lot of territory to explore just using HPF, bass, and mid control. The parametric then can be used to fix a bass or room, or to dial in some particular sound.

Despite the same logo on the front, I find the D800/+ and WD800 to be fairly different sounding heads.

 

[Al Kraft]

I will reiterate my first impression - there is a lot of territory to explore just using HPF, bass, and mid control. The parametric then can be used to fix a bass or room, or to dial in some particular sound.

Despite the same logo on the front, I find the D800/+ and WD800 to be fairly different sounding heads.

There is no question about that! To me the D-800 series has a slightly different (warmer/darker) tonal center and more limited/defined tone shaping that is perhaps easier for a musician of any experience level to use. I found the WD-800 to be inherently brighter (but easily reduced to D-800 warm/dark if you want) and much more of an unbounded palette in terms of tone shaping in many aspects - a true, experienced player's head that allows a lot of experimentation in addition to simply sounding great straight-up out of the box.

 

[Acoustic356]

There is no question about that! To me the D-800 series has a slightly different (warmer/darker) tonal center and more limited/defined tone shaping that is perhaps easier for a musician of any experience level to use. I found the WD-800 to be inherently brighter (but easily reduced to D-800 warm/dark if you want) and much more of an unbounded palette in terms of tone shaping in many aspects - a true, experienced player's head that allows a lot of experimentation in addition to simply sounding great straight-up out of the box.

I found rolling the Passive Mid (band pass filter) all the way down not only darkened the amp up, but it also made it sound tighter and more punchy.

 

[mikeluch]

I typically like "darker" sounding amps, but when I tried the WD 800 against my D800+, I enjoyed what seemed like more articulate notes and that the note "hung on" a little longer. Depending on the bass played, it did at times seem a bit brighter, but I could dial that back a bit with the mid and not having to extensively use the Para EQ.
So far I have only used it at home with my Barefaced Big Baby and Super Midget. Will give it a better trial tomorrow at rehearsal, but overall very positive first impressions.
I have a good feeling that this will work out well, particularly after more experimentation

 

[AMJBASS]

Despite the same logo on the front, I find the D800/+ and WD800 to be fairly different sounding heads.

Agreed! I had a D800 a few years ago, and I find the D800+ to be a different beast. The variable HPF really lets you change the character of the amp.