Low Loss Tone Control

[Ritchie200]

Hello all!

Since I have not read any of the TUT books and know VERY little of the design side, I have a question.  I have not seen a tone stack like the one on the link below.  Of course when you get beyond what little I know about Marshalls, I am pretty much lost anyway.  For all I know, it may be on everything!  It does look interesting.

Thank you in advance!
Jim

http://www.preservationsound.com/wp-content/uploads/2012/01/SimpleToneControlStage.jpg

[MakerDP]

That looks a lot like a James tone stack. It's not exact but the basic structure is there.

Have you read Merlin Blencowe's book on preamp design? It has a really good chapter on tone stacks. It has lots of other really good chapters too!

[Fresh_Start]

I think that's a Baxandall tone stack.

Duncan Amp Tools "tone stack calculator" is really fun to play with.  Fender, Marshall, James, & other tone stacks.

Hey, at least some of the links in the Useful References sticky still work!
http://amps.zugster.net/articles/tone-stacks

Cheers,

Chip

[jojokeo]

I have not seen a tone stack like the one on the link below.  Of course when you get beyond what little I know about Marshalls, I am pretty much lost anyway.  For all I know, it may be on everything!

It is a james/baxandall except for the resistor between the treb & bass pots which affects the mid hump & response, otherwise it's exact (except more standardized values).

[Willabe]

I'm thinking 1MA pots could be used instead of the 3MA pots shown.

But I wonder if that will increase the TS losses?


                Brad   

[kagliostro]

Seems that a 3M reverse Audio pot can be found also now

https://www.tubesandmore.com/products/R-VC3M-RA

https://taweber.powweb.com/store/potsord.htm (wp305RA)

I'm not sure if a reverse one can give problems on that circuit

K

[Willabe]

I'm not sure if a reverse one can give problems on that circuit.

I wonder if you could wire the pot O/X (ends) backwards with a 3MRA? The 1 - 10 markings would be reversed, full off would be 10, full on would be 1, but it might work?

Doug sells 3MRA pots.   


            Brad   

[VMS]

Just wondering here, but why do we need low loss tonestacks?

Usually we need voltage dividers to dump the excess gain on preamps so why not do it with tonestack. 


-v
 

[jjasilli]

Hello all!.  .  . I have a question.


What is your question?


Also, +1 to VMS.  However, this is subjective.  Some players do like James or Baxandall eq circuits in guitar amps.  But generally, this is more applicable to bass amps, or hi-fi.

[jojokeo]

Hello all!.  .  . I have a question.


What is your question?

I think it was?
 

...I am pretty much lost anyway.  For all I know, it may be on everything?

   (Kimo-brah, surprised SG didn't beat me to it?)
 

[MakerDP]

Hello all!.  .  . I have a question.


What is your question?


Also, +1 to VMS.  However, this is subjective.  Some players do like James or Baxandall eq circuits in guitar amps.  But generally, this is more applicable to bass amps, or hi-fi.

According to Melin's book it's the 2nd most used tone stack in guitar amps behind the standard FMV stack.

[MakerDP]

Just wondering here, but why do we need low loss tonestacks?

Usually we need voltage dividers to dump the excess gain on preamps so why not do it with tonestack. 


-v

Well with a low-loss stack you could be a little more precise in exactly how much voltage you are dumping. The swing in your dumps would be less across your settings sweeps in a low loss stack wouldn't they?

[VMS]

Well with a low-loss stack you could be a little more precise in exactly how much voltage you are dumping. The swing in your dumps would be less across your settings sweeps in a low loss stack wouldn't they?

I'm not sure about that and here is my mini rant of the day:

For me the more the treble- middle- and bass-pot does the better. This way I can get different sounds from the amp to suit the music I'm playing at the time.

It sometimes feels like guitar players are afraid to turn the tone knobs and also adjust them more with their eyes than their ears.

Rant over.

[jjasilli]

VMS, I agree with you to the extent that I prefer the FMV tonestack, with it's built-in mid-cut and despite its large insertion loss.  We are not alone, as the FMV tonestack is, and long has been, the benchmark for guitar amplifier tone. 


To get a meaningful tone change, there should probably be about a total 20dB change for each control pot.  The FMV stack provides that (a little less for the mid pot).  The Baxandall stack typically lacks a mid control, because lowering the other two pots "boosts" the mid by comparison.  Presumably the Baxandall-style stack in this thread provides for such relative tone changes, with less overall insertion loss. 


But if you prefer the mid-dip for guitar, then the FMV tonestack fits the bill.  The interactivity of the controls can be off-putting at first.  It just doesn't work like hi-fi eq.  This might make people timid in trying to use it.  But once you get used to it, it's a simple and effective tool.


For bass guitar mid-cut is less of an issue; and for hi-fi it's unacceptable. 


IMHO, insertion loss in the tonestack is not a problem in guitar amps.

[Ritchie200]

Hello all!.  .  . I have a question.


What is your question?

Leave it to my "GOOD BUDDY" jojo to make me pay.  I did leave the door wide open.    Like jojo said though, I have not seen a tone stack wired quite like that.  I thought this was something completely different.  I just wanted to know what it was - that was my question.  This is obviously a dated article.  I didnt even consider the hifi application.  Plus, way back when jojo was born (40's, 30's?), the preamp tubes did not have a lot of gain so loss was important.


VMS, good rant.  I wore out the pickup switch on my strats.  Dynamics and tone, make the songs and the player interesting.  Heck, even Black Sabbath did "Fluff" - played at the end of every ear splitting bludgeoning (Concert) when you walked out.


Jojo.... You sir, had better be careful or I'm gonna tell all the guys here you use a music stand and wear glasses when playing out with your band - old man! Remember, I've got that picture of you playing at your last concert showing the huge....crowd.  I'll post that too if your not careful!


Thank you everyone - except Jojo.


Jim

[jojokeo]

Hello all!.  .  . I have a question.


What is your question?

Leave it to my "GOOD BUDDY" jojo to make me pay.  I did leave the door wide open.    Like jojo said though, I have not seen a tone stack wired quite like that.  I thought this was something completely different.  I just wanted to know what it was - that was my question.  This is obviously a dated article.  I didnt even consider the hifi application.  Plus, way back when jojo was born (40's, 30's?), the preamp tubes did not have a lot of gain so loss was important.


Jojo.... You sir, had better be careful...

Thank you everyone - except Jojo.

Nice, that would make me your & my dad's age! But that's okay because we're all working our way there and arrive sooner or later. BTW, since when are you concerned with tone stacks? It was you that reminded me that you just swipe them all the way up in one slick fluid motion then turn around facing the crowd with an evil grin and a power E chord to wake the dead and El Diablo himself!?

Insertion loss is actually very important in certain respects. If anyone plays around with placement only then you know & understand what a profound affect this has even without voltage dividers and such. In a simple BFDR, Basman, Vibro, etc all it takes is placing after the two stages rather than between and the change is dramatic. Forget about Fender shimmery cleans as it would never occur without the accompanying insertion loss AND mid notch both working  together, IMO.

Jimbo, you're not welcome 

[tubeswell]

As for 'low-loss', it also depends on the source impedance driving the tone stack. The lower the source impedance, the lower the tone stack loss will be.


You could 'lose' your passive tone stack altogether and go for active tone controls (e.g; presence and resonance controls sourced from the global NFB loop, or active controls based on local feedback loops) - that way you would have boost instead of loss.

[MakerDP]

Well with a low-loss stack you could be a little more precise in exactly how much voltage you are dumping. The swing in your dumps would be less across your settings sweeps in a low loss stack wouldn't they?

I'm not sure about that and here is my mini rant of the day:

For me the more the treble- middle- and bass-pot does the better. This way I can get different sounds from the amp to suit the music I'm playing at the time.

It sometimes feels like guitar players are afraid to turn the tone knobs and also adjust them more with their eyes than their ears.

Rant over.

Let's be real about this... the reason the FMV tone stack is the most common tone stack and is most people's "favorite" stack is because it is the cheapest TMB stack to mass produce and so it has become "the standard" that all other stacks are compared to.

If you've compared it to other stacks and it is still your favorite, that's cool but don't discount the influence of your familiarity with how the knobs react when you turn them and the ease with which you can find a setting that works for you is based on how often you've used it because it was on nearly every amp you ever owned.

"rant" over...

[jjasilli]

@jojo:  I think we're saying the same thing in different ways.  The insertion loss itself can be made up by a tone recovery stage; or as you say, the placement of the tonestack within the gain stages.  However, the tonestack will have less effect the further downstream it is, as tone will have been substantially shaped before it gets to the tonestack.  Also tone controls have different affect pre- vs. post- distortion.  But whatever the gain stage topography, the stack's insertion loss can easily be accounted for either by accepting it, or by actively re-boosting it.  However approached, it's often a practical necessity to produce a mid-dip to avoid a muddy el guitar sound, which dip comes ready-made in the FMV stack.


@ tubeswell:  i) +1 to source impedance.  There's a recent thread on the Bassman 5F6A cathode driven tonestack, which has signifigantly less insertion loss than the plate driven stack.  ii) Going active is another option, but the purpose of the circuit first posted by Ritchie200 is to have low insertion loss in a passive eq circuit.   This may be useful for hi-fi where an extra gainstages are usually avoided, because they detract from signal fidelity by adding to harmonic distortion, hiss & noise, etc.


@makerdp:  it is possible that the FMV tonestack is popular by sheer market force.  But my belief is that it is popular due to the merit of the mid-dip tone.


 

[jojokeo]

However, the tonestack will have less effect the further downstream it is, as tone will have been substantially shaped before it gets to the tonestack.  Also tone controls have different affect pre- vs. post- distortion.  But whatever the gain stage topography, the stack's insertion loss can easily be accounted for either by accepting it, or by actively re-boosting it.  However approached, it's often a practical necessity to produce a mid-dip to avoid a muddy el guitar sound, which dip comes ready-made in the FMV stack.

Hmm what you're saying makes sense and has validity but in my experience when the stack is earlier & placed after the first stage as in a typical Fender BF amp (using as an example) and you were to add an additional stage or two afterwards, the tone controls seem to have less effect not more on the overall amp's control after doing this. And it seems to help keep the tone & response in more of a Blues-type of amp category, feel, and sound - to me.

When there's several preamp stages either cascaded or separated by gain pots (with or w/out a CF stage in there at some point) feeding the tone stack after all of this I get better overall control of the signal and I get a much truer rock/high gain affect that has a greater "dialing-in" range to the overall sound & tone by the stack being placed later in the circuit.
 
There is no "right or wrong" here. But for me, this is my experience while trying the same basic ideas used for some of the Dumble influenced & many other circuits we've all seen here. YMMV?

Regarding tone stack types, I've spent countless hours using the Duncan program as well as experimenting & playing with many types & values yet seem to usually go back to the tried & true FMV stack topography. But some designs require slight adjustments with a bit more or less bass here and/or mid response there depending on the design. I've also done many bypassing, partial bypassing, and lifting as well as subbed for fixed values like tubenit's done a few times here and there (when he feels a Bass control isn't necessary but still designs a fixed value to set it at a certain point). This is basically setting high & low pass filters also which I'll also do in my effects pedals designs when I feel is needed for a certain response. So for me I always have a starting place and make final adjustments from there during the final tweaking & voicing process I go through with a new design.
 
*You JJ, Maker, & Tubeswell all make valid (obvious) points that should not be left out of the conversation for consideration.

[jjasilli]

When there's several preamp stages either cascaded or separated by gain pots (with or w/out a CF stage in there at some point) feeding the tone stack after all of this I get better overall control of the signal and I get a much truer rock/high gain affect that has a greater "dialing-in" range to the overall sound & tone by the stack being placed later in the circuit.


I think we are are at a point where subjective preference is mixed (blend pot?!?  ) with the objective reality of the circuitry. It is axiomatic that the first gain stage(s) set the tone for the amp.  And, if some of the signal band is attenuated or removed early, then we can't get it back later.  It's like sawing-off too much wood.  We can always trim it more, but we can't add wood back later.

Guitarists may opt for a pedal or rack unit with EQ units both before and after an overdrive or distortion box.  Typically too much bass or mids into an OD/distortion circuit results in muddy output.  So it's nice to trim lows on the way in.  OD/distortion inherently generates its own new set of harmonics; i.e. overtones that were not in the original signal.  It's nice to have EQ after that to adjust the overtones.


In contrast, guitar amps typically have only one adjustable EQ point*.  EQ is going on at every stage, but it's hard-wired and non-adjustable except for the tonestack.  The tonestack has to go somewhere.  You seem to prefer cascading gain stages.  They tend to produce a smoother, creamier type of OD for Blues-Rock; or OTOH hi-gain square-wave clipping, for Metal-Shred.  In this topography I agree that it makes sense to put the tonestack late in the chain of gain stages, to have control over the result of the distorted output.  But this relies on the signal band being pre-adjusted for you by the hard-wired R-C circuits connecting (and blocking B+ DC) in the earlier gain stages. 

*Presence controls; bright switches; etc.,  are exceptions for additional flexibility.

[Ritchie200]

There is no "right or wrong" here.

Oh yes there is.  I am always right.  You are always wrong.  Oh wait, that's what my wife says....


But I digress, there is really only one tonestack.  I'll post it below so Jojo can blow it up, print it out, and set it on his music stand - after he puts on his glasses.


Great discussion guys, thanks again!
Jim

[tubeswell]

Yeah the 1967 is a classic circuit, but I vote for taking one of the unnecessary triodes (and volume controls) away from V1 and using that triode as a DC-coupled CF in conjunction with the 'volume recovery' stage in order to drive the tone stack with low source impedance.  And you'll still have the 12AU7 to drive the grids of the KT88s - making full use of its bandwidth capabilities. (and you won't have to change the NFB insertion point)

[jojokeo]

And, if some of the signal band is attenuated or removed early, then we can't get it back later.  It's like sawing-off too much wood.  We can always trim it more, but we can't add wood back later.

Not true, and bad analogy. Our primary low level high impedance signal is practically the same when being amplified the first time as an already amplified signal that is attenuated some and then re-amplified once again later. There isn't anything "lost", the musical signal information didn't just vanish away (like a piece of cut wood). It may not be "exactly" the same but definitely enough for tones or effects we're after in a guitar signal and it may actually be preferred and have positive uses. I'll use noise and/or notch filters as an example which is a way to specifically target & limit or enhance a specific frequency or range yet maintain the important majority of primary signal.

You seem to prefer cascading gain stages.

Not necessarily, it depends on what I'm designing for or working with to get what I want on a specific quality, sound, tone or response.
 

Oh yes there is.  I am always right.  You are always wrong.  Oh wait, that's what my wife says....

But I digress, there is really only one tonestack.  I'll post it below so Jojo can blow it up, print it out, and set it on his music stand - after he puts on his glasses.

Your wife IS right, you are always wrong...once again! Now some of us actually read music & notation, make notes for arrangements due to limited practice & rehearsal times and/or complexity of music, help to remember song lists, words in songs, etc. and due to corneal rigidity that affects everyone as we age gracefully over those rare few idiot savants that require no such things, are indeed appropriate to help by any means necessary to put on a good performance and save one's self from the ultimate embarrassment of screwing up royally on stage is all good in my book my bruddah.   
 

[jjasilli]

There isn't anything "lost", the musical signal information didn't just vanish away (like a piece of cut wood). . . I'll use noise and/or notch filters as an example which is a way to specifically target & limit or enhance a specific frequency or range yet maintain the important majority of primary signal.
You are correct that attenuated signal is not literally lost, but I'm not sure that applies within the context of guitar amp circuits.   Using refined active EQ, a specific signal band that was attenuated, can later be re-boosted into the main signal.  This is possible in the studio, or with pre- & post-distortion parametric EQ boxes in a rack or on a pedal board (which I mentioned in a prior post).  I'm not sure that guitar amps contain the circuitry to recover a signal band.  Typically if we drop lows, mids or hi's in a guitar amp, they stay dropped relative to the rest of the signal.  Perhaps someone can identify such a circuit inside a guitar amp, possibly a Mesa Boogie, Marshall or Soldano.


Now some of us actually read music & notation, make notes for arrangements. . .
I saw Phil Lesh & Friends in concert including Robben Ford and personnel from Little Feat.  They really rocked-out.  Each member of the band had a music stand and were reading from it.  It was a bit disconcerting at a rock concert to see the entire band reach in unison to turn a page!

[shooter]

the entire band reach in unison

As a visual artist I would find that more artistic than if they were all outta sync 

now visualizing a fat man in a bathtub, THAT is disconcerting 

[tubeswell]

It was a bit disconcerting at a rock concert to see the entire band reach in unison to turn a page!

Yep its a real PITA when you have to turn your own pages whilst performing. The real pros have other people whose job it is to stand there and read along and turn the pages for you LoL


(Edit: What am I saying? Everybody is moving to iPads these days)

[jojokeo]

   I don't EVER turn a page...during the song at least! (I don't have three arms & hands) 
 
*see what you started Jim?! I know you're laughing your butt off...

JJ - not sure we're on the same page here? The guitar's signal is very small. A single tube or transistor increases it up significantly...I'm not trying to say that a tone stack can or will do it alone by itself? So my prior comments were made in this respect that when/if a signal is attenuated that it can be increased again (via more gain stages) and then refined further if wanted with high or low pass networks, etc... as much as one would like to. You then could even create additional frequencies from the various orders of harmonics, filter them, and play with them in all sorts of manner (as done with certain effects pedals). This is getting way out there beyond the scope of this thread but I'm merely pointing out many ways that frequencies & signal can be manipulated as a whole.

[Ritchie200]

  Yup!


Jojo and JJ, you are both wrong and I am right!!! (where is my wife....)


Imagine if you will.... Dolby B, C.  You can taketh away and you can giveth back!


Not a "guitar amp application" you say?  I would say that every rocker from Page, Blackmore, Beck, May, etc., etc.... used various forms of a treble booster.  Each had different tonal results but with the same sonic result - lots of drive without picking up every radio station in town with uncontrolled feedback.  How?  Dolby 101.  You boost the highs from the guitar and attenuate them at the amp.  Result, low noise floor, high gain.


Jim

[jojokeo]

Nice! That even shows my "good" side?  Don't know how you hacked that one off my wife's phone but since we're in a sharing mode I was actually able to find the long lost deep track you told me about when you once made an appearance with Bon Scott before he moved on to AC/DC? If I'm not mistaken you said you were only able to groove next to the drummer on this one since your Major was broken down (once again) at the time and you couldn't find a competent amp tech handy?

https://www.youtube.com/watch?v=t2B8KSDKcIM

[Willabe]

Hey, I don't think that's Jojo, I think that's the real Jimbob your finally showing us! About time! We'll still be your friends.


            Brad     


 

[jjasilli]

You boost the highs from the guitar and attenuate them at the amp.  Result, low noise floor, high gain.


Yes, you can do that so long as you go outside the guitar amp.  That is granted.  But this thread was about a low loss eq circuit inside an amp. 


Also your low loss circuit calls itself a tone control.  This is a hint that it concerns stereo amps.  "Tonestack" is a word unique to the guitar amp world, and not used elsewhere.  No one calls the tone controls on their stereo a tonestack.  And in the studio, tone controls are often more complex, and called EQ. 


Also, guitar amps usually have only passive tone circuits.  They only attenuate.  Gain circuits inside the amp tend to boost the entire signal range.  So, the attenuated band stays dropped in relation.

Re Dolby: Yes, if you actively boost a frequency band you can drop it later passively.  But active tone shaping does not usually happen inside a guitar amp.  It is possible that the Mesa Boogie model, copied by Carvin & Acoustic, with parametric sliders, has active EQ in addition to a tonestack.  I'm not much familiar with this amp.  But it might be an exception along the lines that you & Jojo are saying.

[jjasilli]

Found it.  The Mesa Boogie Mark IIb is an example of what you guys are talking about, inside a guitar amp.  http://el34world.com/charts/Schematics/files/mesa_boogie/Mesa%20Boogie_Schematics.htm


Note that the preamp schematic is drawn "backwards", with the input on the right side.  Starting off Fender like, the FMV tonestack follows the 1st gain stage.  This allows for pre-distortion eq. Then comes 4 cascading gain stages, with rather elaborate, semi-adjustable tone shaping circuits between these stages.  Then comes active SS parametric EQ. This would enable selective boosting of previously attenuated signal bands, inside the guitar amp. 

[jojokeo]

Good find JJ, I can build or repair an amp from either direction fine but trying read a schem backwards is like trying to hit a curveball from a lefty...something that you don't see all that often.

[Ritchie200]

Yes, you can do that so long as you go outside the guitar amp.  That is granted.  But this thread was about a low loss eq circuit inside an amp. 

Oh who's paying attention to those details....

The first Major, the Pig, had active tone controls.  Actually it was call the "Marshall 200".  Mick Ronson used them through the Bowie Ziggy Stardust years both in the studio and on tour.  They sold about 5 of them because everyone complained about how they sounded.  That's when Marshall had GEC come up with a more traditional tone stack - but was not traditional at all!  It was perfect.....

Jim

shut up jojo.....

[jjasilli]

"All things must   pass. "


Aspen Pitman agrees with Ritchie:  https://books.google.com/books?id=JT1I7Ld76YsC&pg=PA75&lpg=PA75&dq=marshall+200+active+tone&source=bl&ots=It19LUf2bj&sig=Y6ImLCJCZLfb6w7htZUu3_rga7A&hl=en&sa=X&ei=6nIyVZ6gFJKHgwTj8oL4Bw&ved=0CEoQ6AEwCg#v=onepage&q=marshall%20200%20active%20tone&f=false


@makerdrp:  Also it seems to me that for a guitar amp on stage, the FMV tonestack is easier to use on the fly, than non-interactive tone controls:  Marshall 200 "Tone" Controls

[jojokeo]

Oh who's paying attention to those details....

 - but was not traditional at all!  It was perfect.....

Jim

shut up jojo.....

*somewhere between okay and perfect?   

"The first ones were simply labeled Marshall 200 and billed as the 'World's most powerful distortion-free amplifier.' The first Plexi-paneled amps were a design departure form the 100w series, featuring 'active' tone controls are rather unmusical because each EQ band is separated and controlled by a preamp stage - and is sucking tone like little FX loops. The passive approach is more direct and player-interactive. But if you wanted LOUD and dYnAmIc, this was the amp."

[PRR]

> a Baxandall

Bax described a *negative feedback* tone control.

The passive 20dB loss has been ascribed to James, though others proposed similar plans.

This one is very much in the James family. The canonical James has a 100s-K resistor between B and T wipres with output at the T wiper. This does not. I had assumed this cross-resistor reduced interaction, but a hasty sim suggests it is quite usable as shown.

> the reason the FMV tone stack is the most common .... is because it is the cheapest TMB stack to mass produce and so it has become "the standard"

Cheap, yes. Also avoids a coupling cap.

But IMHO *the* reason it is well-loved is that it likes to boost bass and treble, and notch midrange, in a way that makes a naked steel string sound "better", bigger, brighter. More orchestral, less solo soprano. It complements the strong mids of a naked guitar string. The James/Bax can do the same, almost, but more of the rotations are not much used, and there is no 700Hz notch to mute the strong 500-1K output of the strings.

[jojokeo]

It's been 6 or 7 years since I did a lot of post EF86 tone control experiments and the James/Bax loaded down the signal more than my current Fenderish stack I like in most of my amps. In actuality the Marshall puts more load than a Fender stack too when using that 33k slope resister that's so common and combined with both 0.022 caps for the bass & mid, it doesn't have as much low end either. Now combine that with the small 0.68uF Plexi bypass cap and there is even less low end and gain. End results are that Fender values + stack has much more gain than Marshall's. Believe it!

So "perfect"!? Definitely not for all applications. But when used as Jim M used this for his amps that also got used in post cf stages then it works beautifully due to prior stages' much lower impedance from loading it down.

[jjasilli]

@PRR &makerdp:  The cheapest tonestack is a treble bleed.  Tweed tonestacks are also cheap; reasonably effective; and preferred by some.  Blonde tonestacks (in contrast to stacked Blondes) have not endured.  See, e.g.: http://amps.zugster.net/articles/tone-stacks  In fact many tonestacks have come & gone.  But the FMV endures.  So I agree that it has merit.


@jojo:    In actuality the Marshall puts more load than a Fender stack too when using that 33k slope resister. No, the 33K slope resistor is cathode driven, not plate driven.  The result is substantially less load & less insertion loss. See:  http://el34world.com/Forum/index.php?topic=18505.msg189191#msg189191

Also I suspect that the 0.68uF bypass cap has the purpose to "cut bass" > overdrive to avoid a muddy overdrive tone, per prior posts on this thread.

[jojokeo]

I don't want to belabor the point much further but here is two screenshots for disbelieving eyes below. Now here's the caveat which you cannot ignore: to compare apples to apples you must use the same Zsrc for each for a true comparison and make things equal for both. The top line / sweep curve in each screenshot is "the Fenderish values I like most" and the lower is the beloved Marshall (losing) tone stack. My Fenderish stack has more Bass & Treble gain in both while also showing a slightly lower mid dip. One is displaying at the Fender stated 38k & the other at 1.3k - so it's as if the Marshall stack was put into a Fender position and if my Fenderish stack was placed in a Marshall position.

Here is one of my amps which has the benefit of some of what I'm describing, however it is also multi-stage biased which pronounces the differences in this case. This biasing system is what separates things apart. But the real truth is in the testing, listening, and playing using different stacks in the same amp to form your own conclusions, however the screen shots support my experiences in not just this amp.
http://el34world.com/Forum/index.php?topic=9954.msg125523#msg125523

[Ritchie200]

"All things must   pass. "

Yes, but you notice the truly special things in life tend to be those fleeting moments of brilliance!

I like how he clapped at the beginning of the video to show the volume!   
The bass got very "blatty" but the treble sounded good.

Jim

Its like a shining beacon on the mountain....a silver mountain....the man!

[jjasilli]

Jojo: not sure what you're comparing.  Typical Fender is 12AX7 driver with 63K Ohm Plate Impedance > 100K slope resistor; then, 250pF Treble Cap; 250K bass pot & 10K mid pot (Though 5F6A uses 25K) > 1M following impedance.  Your charts show substantially different component values.  Also, you show all controls dimed, which is not typical use, and masks the FMV mid-dip.


For typical Fender component values, the Duncan Tonestack Calculator shows the signal curve straddling the -20dB line with all controls @ 5; and still a mid-dip below -20dB with all controls dimed. This is substantially different from your curve plots.



In my experience a 12AX7 plate-driven tonestack, with less than a 100K slope resistor, is dark with inadequate treble.

[jjasilli]

@Ritchie:  https://www.youtube.com/watch?v=A5cneCgNA9U

[Ritchie200]

Haha!  You got it!


Actually it can be fixed.  The same amp....