Separating tone stack across multiple gain stages

[jlapalme]

Hi,

Many of the classic passive tone stack designs create interactions between the controls.
Is it possible to separate the control of Treble, Mid and Bass across multiple gain stages in order to minimize interactions ?
In order words, is it possible to have 1 control per gain stage ?

Cheers,

James

[shooter]

the B & T should be doable, M probably needs some math 


surf up band pass filter, or band trap, for audio.  maybe try tone cut

[shooter]

Here’s a Bogen example where T and B are “basically” individual circuits.

Guessing T is C8,9 & R4
B is C10,11 & R14,3
Again guessing T&B are “mixed” with R15,16

Unkown;
R13

[kagliostro]

There is an UK Kit by Ampmaker that has the Treble & Bass control after the first stage and the Middle control after the second stage

http://www.ampmaker.com/store/Double-Six-switchable-power-amplifier.html

http://www.ampmaker.com/infocentre/forum-7.html



Franco

[sluckey]

Is it possible to separate the control of Treble, Mid and Bass across multiple gain stages in order to minimize interactions ?
In order words, is it possible to have 1 control per gain stage ?

yes

[jjasilli]

I think the passive Baxandall circuit is non''interactive.   It can also be made active.  OTOH simple bleed circuits can be placed between gain states; but if not precisely filtered, their frequency ranges might overlap. Not to mention presence controls in the feedback loop.


Many believe that interactive tone controls are a good thing. 

[PRR]

> passive Baxandall circuit is non''interactive.

No.

> Many believe that interactive tone controls are a good thing.

Yes.

[jjasilli]

Interesting points on Baxandall:  https://www.thegearpage.net/board/index.php?threads/whats-a-baxandall-tonestack.805784/


Also: there's parametric EQ, once somewhat popular on the face of a few guitar amps. 


I think some Fender Tweed amps had tone controls between different gain stages.

[jlapalme]

I think the passive Baxandall circuit is non''interactive.   It can also be made active.  OTOH simple bleed circuits can be placed between gain states; but if not precisely filtered, their frequency ranges might overlap. Not to mention presence controls in the feedback loop.


Many believe that interactive tone controls are a good thing.

Why ? What is the advantage ?

[jjasilli]

N.B.:  I overstated the point re Baxandall - it's not "non-interactive", but less interactive then FMV.


Probably players like the interactive FMV tonestack, because it provides good tone changes quickly with little fiddling.  Effective for live performance.  Contrast with, say, 15 band parametric EQ.  A player cannot fiddle with 15 sliders on stage.  That works better in the studio. 


E.g., if you want more bass, you may need a tad more treble to compensate.  That could involve adjusting 5 or so parametric sliders, or 2 Baxandall knobs, or 2 tone controls located in different gain stages.  With the FMV tonestack, just turn up the bass, and a little less treble will bleed to ground also.  In practice, it works well for a player in spite of itself; though it would not be suitable for studio mixing.

[d95err]

I agree with the post above. The FMV tone stack just works. Almost all settings provide useful tones and it’s very easy to dial in the tone you want.

The mid dip of the FMV tone stack integrates well with the mid focus of the guitar speaker and with the mid focus of a distorting preamp.

Most amps I’ve tried with e.g. ”active three-band EQ”, are very difficult to dial in. They usually don’t have that natural mid dip and the useful range of each control is very narrow.

[DummyLoad]

interesting semi-para i've thought about building. kind of off topic, but maybe something to draw other ideas from.


--pete

[shooter]

Pete, we have a huge hog processing plant close by, I can probably get all kinda tails for that circuit 

fwiw;
if you want the "theory of how/why" this might be fun 
https://www.electronicshub.org/active-low-pass-filter/

the high-pass is linked also

[Backwoods Joe]

There used to be a amp maker in Raleigh NC that had a great sounding amp (can't remember the company name) that used a layout some thing like this; First triode, clicker cap stack ( for bass) then another triode or two and a simple mid circuit and a vox type treble cut before the output tubes. Never saw the exact schematic, just got a quick glimpse in the back of the combo.