Ultimatest Passive Tone Control Network based on James-Baxandall's topology wanted

Most ultimate Passive and Active (NFB) Tone Control Network based on Peter James-Baxandall's topology

This was the developer:
https://www.aes.org/aeshc/jaes.obit/JAES_V44_9_PG796.pdf
Around his topology there are a very extrem amount of proposals about google - thus this don't help me.
here some examples and a basic article (overview)
Tone control circuit - Wikipedia, the free encyclopedia
https://web.archive.org/web/20090225070322/http://www.schmarder.com/radios/tech/tone.htm
https://web.archive.org/web/2007012...l.gob.pe/publicaciones/rvargas/red-activa.htm
(analyses of a Baxandall-type Active-Tone-Control Network -
Ing. Ramón Vargas Patrón Lima-Peru, South America July 23rd 2004)
https://web.archive.org/web/2012121...omcast.net/~stphkeri/NegativeFeedbackTone.pdf
Baxandall Tone Control Using CA3140 Op-Amp | Circuit Diagram
http://www.ti.com/lit/an/sloa042/sloa042.pdf
post #30+31 under
https://www.diyaudio.com/community/threads/looking-for-very-good-tone-control-schem.21307/
and post #1 under
https://www.diyaudio.com/community/threads/a-usable-tone-control.199130/

There are two basically topologies:
1) passive version (between two line gain/buffer stages) - go to first attachment.
2) active version - i. e. in the negative feedback loop - frequency dependent NFB (from an inverted mode amplifier and from a non inverted mode amplifier - both in voltage amplifier gain stages (preamp) and power amplifier stages in cases without separate preamp line stage) - go to second attachment.

I need the best circuit topologies for both applications. The most important features for me are follow:
1) the insensibility (immunity) against electromagnetic hum sources and against microphonic effects.
This means, low impedance character (i. e. the contrary of such circuits, where the variable resistors/pots have values between 5 meg-ohm and 10 meg-ohm, often to find in tube amp/preamp stuff and vintage tube audio devices).
2) the establishing of any cutoff frequencies for the lower and upper area

Where I can find such circuit topologies both here on diyaudio and by commercial devices?
Thank you for your advices
 

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  • P.J. Baxandall Passive Tone Control.pdf
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  • P.J. Baxandall NFB Tone Control.pdf
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  • P.J. Baxandall - in Memoriam.pdf
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He used pots that are really not easily found today and was limited to high impedance valve circuitry.
low impedance pot is the smallest issue. Here I intend to use a rotary switch like ELMA (Switchable Attenuator/Rotary Switch) or an relay controlled solution.
A selection can be found under
http://www.diyaudio.com/forums/solid-state/153935-best-audio-relays.html
http://www.diyaudio.com/forums/soli...nny-giles-tkd-vishay-more-whats-your-fav.html
You can build a classic Baxandall circuit using opamps and switched low value resistors.
Unfortunately only by using of power op-amps.
 
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Try this. You can use almost any opamp as the current requirements are not too severe.
 

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@ tiefbassuebertr

Hi, your title is misleading, as you then go on to say you're looking for active too ;)

I've always known him as Peter Baxandall, now i know his middle name :)

You might like to take a look at Page 27 of Doug Self's Precision Preamplifier Tone control circuit in here Self_on_Audio_Second_Edition.pdf

This should be available from his www, i think !

It's what i built & use in my PreAmp, which i've had for many happy years. You can change the caps around the pots to suit the centre frequencies you desire, i did.

Use high quality BiPolar OpAmps for low impedance work ;)

You should place a buffer on the output as well.
 

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Some time ago I looked at non inverting Baxandall type tone controls, and after some searching, I found these. The idea isn't new, it was used in the Crown IC150 pre amp of the early '70's.

The non inverting type have gain (I've set it at 2, Crown used a gain of 11 I think), and a high input impedance, so they don't need to be driven from a buffer stage. With the values I've shown, the boost is twice that of the cut, which some people might not like, but I think it is probably more useful than similar cut and boost values. A simple DPDT switch will defeat the tone controls and give a flat response.

Note that the two attached drawings have different R&C values. The schematic is shown with 100K pots, and the curve drawing with 50K pots (both linear).

Paul Bysouth, Sep 2011
 

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Thanks for all hints.
Tiefbass check the Luxman integrated Amps for `` Duo Beta `` tone control circuit !
Best Regards
That was an excellent advice. In the attachement the schematic of the Baxandall part from Luxman's L-550 Class-A integrtated amp. Schematic you will get about "hifi engine" for free after login. If I transform the line cascode stages to power amp stages for low impedance headphones, I can reduce the variable resistor values and that one of the associated devices (by the capacitor values I need enhancing) down to values of 1-5 percent (this means 50 ohms instead 5000 ohms and as consequence very low sensitivity against unwanted microphonic effects).
Also a cuttoff selector is present (Luxman call this "Turnover Select")

Also the APD Holeman I will study exactly, if I have more time
http://homepage.mac.com/planet10/TLS/downloads/AptHolmanPreManual.pdf
http://www.diyaudio.com/forums/solid-state/48419-why-does-apt-holman-preamp-sound-so-good.html
http://homepage.mac.com/planet10/TLS/downloads/AptHolmanPreManual.pdf

RIAA Equalizer circuit
Phonograph preamplifier network with infrasonic cutoff response
Active load circuits
Phonograph preamplifier network with infrasonic cutoff response
 

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Mr Douglas Self say here : Douglas Self Site

"Tone-controls cause an audible deterioration even when set to the flat position."
-This is usually blamed on "phase-shift". At the time of writing, tone controls on a preamp badly damage its chances of street (or rather sitting-room) credibility, for no good reason. Tone-controls set to 'flat' cannot possibly contribute any extra phase-shift and must be inaudible. My view is that they are absolutely indispensable for correcting room acoustics, loudspeaker shortcomings, or tonal balance of the source material, and that a lot of people are suffering sub-optimal sound as a result of this fashion. It is now commonplace for audio critics to suggest that frequency-response inadequacies should be corrected by changing loudspeakers. This is an extraordinarily expensive way of avoiding tone-controls.-

And I agree with him 100% !

Actually I have idea to experiment and implement this Luxman`` Duo Beta `` tone control circuit on the one of mine older conventional designed DIY PP tube power stereo Amp, simply returning GNFB loop from OPT outputs via tone control circuitry to the input tube differencial gain stage ,in the same manner as Luxman did on the countless number of SS integrated comercial Amps .

Best Regards
 

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  • Baxandall, Peter James - In Memoriam JAES_V44_9_PG796.pdf
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My problem is that my tda 2040 is sounding good with tone control.but for this I used Tl072 which sounds quite noisy ,dont have other good chips too.My dth receiver aint that musical.Tda 2040 alone doesn't give me musical sound.So I have decided to go for standalone Lm1875 .I want mid range n treble frequencies .I will be very thankfull to u if u pl z provide any change from original circuit.How far can a passive tone control help?.
 
No changes necessary, AFAIK. The tone circuit output needs to see a high impedance. The 1M seen in the LM1875 datasheet app should be enough, or another op amp stage.
How far can it help? That can be hotly contested. I'm convinced tone controls can help SQ. And I follow the rule that if tone controls need to be turned way up, something else is wrong with the system. I have maybe +4dB on the treble and +1 for bass (I'm sure I have eardrum scar tissue from a bout with meningitis. Tinitus also. Hence the treble boost.). And they stay there. If a particularly worse recording gets played, I'm almost always reaching for the volume knob. That's rare though.
If you don't think tone controls are just for sissies, you might want to have a look at this thread: A usable tone control