Which Graphic Equalizer Circuit Topology provides best Sonic Quality ? "Constant-Q" ? - diyAudio
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Old 6th December 2016, 11:07 AM   #1
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Default Which Graphic Equalizer Circuit Topology provides best Sonic Quality ? "Constant-Q" ?

There are several topologies for graphic equalizer.
Good known is the common 'gyrator' tuned circuit - mostly to find in commercial devices. This graphic EQ circuits have a Q, that is dependent on the setting of the pot (non constant Q) - actually a disadvantage for such a topology - go to
How to build 10 Band Graphic Equalizer - circuit diagram
6 BAND GRAPHIC EQUALIZER CIRCUIT USING 741 OP-AMP SCHEMATIC DIAGRAM | Wiring Diagram
10 band equalizer based on LM833
A better solution seems to be the less common "Multiple Feedback Bandpass Filter" topology for each frequency. This one maintains the same Q (i. e. same bandwidth) at all settings of the pot, and this I have found by Rod Elliott - go to
Expandable Graphic Equaliser
and
Musical Instrument Graphic Equaliser

The only commercial products I know, which have this topology, are the models "RE27" and "RE14" from RAINE so as ARX EQ260 - go to
Constant-Q Graphic Equalizers
http://electroff.narod.ru/docs/files1/constanq.pdf
http://www.rane.com/pdf/old/re27man.pdf
http://www.ece.rochester.edu/~zduan/...Equalizers.pdf
Rane RE27 Realtime Equalizer | eBay
ARX*FAQ - all about Graphic EQs and why ours are better
ARX EQ260 dual channel 1/3 octave graphic EQ

Pros and cons of constant-Q and non constant-Q are discussed here - unfortunately not in order to the sound quality:
https://www.gearslutz.com/board/geek...onstant-q.html

Which graphic equalizer topology I should prefer in order to became the best sound quality ?

And a second question:
What is important for select the appropriate operational amplifier IC's for each topology (there are an extremely wide range on the marked in the meantime and I have heard, that both MFB- and gyrator applications need other requirements in order to the internal circuits than linear applications like preamp/line stages and RIAA head amps)?

I want to have an 1/3 octave equalizer with adjusting range of -10 to +10 db or more for an use in problematic listening room environments.
This provides an easy verification from the possibilities of sound improvements.
In the moment I want to have such an equalizer for the linearization the transmission of a certainly rail from an expensive horn system between 60Hz and 600Hz (increase between 60Hz and 200Hz and decrease between 200Hz and 600Hz) - but without suffering of the sonic quality at whole. - go to the third image (left graph) at post #3 under
Acapella Sphaeron Excalibur and new IB Subwoofer with 4 pcs. Precision Devices PD184

Thank you very much for advices.

Follow URLs don't provide the wanted hints:
5-BAND EQ: Constant Q or conventional topology?
Custom Equalizer Design needed
10 band equalizer based on LM833
So few comments on eq
Graphic Equalizer
Graphic equalizer
DIY Graphic equalizer?
EQ with BJT as Gyrator
Graphic 1/3 Octave Tube Equaliser

Last edited by tiefbassuebertr; 6th December 2016 at 11:19 AM.
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Old 6th December 2016, 03:30 PM   #2
adason is offline adason  United States
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I know this is in analog section, but when it comes to 31 band eq, I would go digital...

Last edited by adason; 6th December 2016 at 03:45 PM.
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Old 6th December 2016, 03:35 PM   #3
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Once again no definition of 'best'. sigh...
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Old 6th December 2016, 03:55 PM   #4
Zero D is offline Zero D  United Kingdom
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Yes Constant Q is the best at staying constant !

I designed & built a bass 1/4 octave EQ many years ago, & will tell you this.

More bands require higher Q & that requires OpAmps with higher bandwidths. Otherwise they won't perform as expected ! But, that can lead to oscillation, so great care needs to be taken with the circuit design.

Also, splitting & then combining the bands into multiple odd/even sections, helps too.

Fortunately, my EQ works fine

Unless you find, or copy a circuit, & build the PCB & it Exactly, you could have problems.

I've used Rane many times over the years, & highly recommend them. I would save yourself a lot of time, & possibly trouble, & just buy one, maybe second hand
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Old 11th December 2016, 04:45 PM   #5
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Good information - thank you for your reply. I will looking arround for two pieces RE27 from RANE in used condition - like this no longer available offer
2 Stück Rane RE-27 EQ und Analyzer incl. 1 original Messmic für FOH oder Monitor | eBay
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Old 21st December 2016, 06:45 PM   #6
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There are other models of such equalizer devices from RANE, e. G. GE30, ME30, ME60, GQ30 and GE60.
Rane GE 30 Graphic Equalizer 2 x 30 Band, defekt | eBay
Rane ME 30 Graphic Equalizer 2 x 30 Band | eBay
RANE GQ 30 - 2 Stück graphic equalizer (kein Yamaha EQ 550) | eBay
RANE GQ 30 - 2 Stück graphic equalizer | eBay
Rane GE60 Equalizer | eBay
RANE GE 60 stereo 1/3 Oktav Equalizer mit Hoch- und Tiefpass | eBay
Rane Made in USA ME60 Rack Mountable Dual Channel Graphic Equalizer | eBay
I asume, "60" means two-channel and "30" one-channel version.
But what about the differences concerning sound quality between this models ?
And which operational amplifier IC's was used from RANE ?
Thank you for advices.
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Old 10th January 2017, 01:42 PM   #7
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There are not to find images from inside of RANE equalizers on the web. Who can upload some images of various models like GE60, RE27 etc ?
The only image of RANE GE60, which I discover under
http://www.livesoundint.com/archives...uest/quest.php
is no high resolution unfortunately.
Thank you very much.

Last edited by tiefbassuebertr; 10th January 2017 at 01:49 PM.
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Old 10th January 2017, 01:56 PM   #8
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is this for interest or are you wanting to steal IP off them?
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