Adding bands to an equalizer circuit?

c12mech · 23rd March 2011, 01:23 AM

If I were to build a 10 band EQ similar to this one:

Graphic Equalizer Circuit for 10 Frequency Bands

how would I make it a 20 band circuit? Is it just a matter of adding more of the same IC sections and components or is there more to it? I've looked around and don't seem to find a lot of info on building anything more than the 10 band EQ shown. I'm sure it is probably overkill but it is just something I want to try.

Any help would be appreciated.

sofaspud · 23rd March 2011, 02:08 AM

Yes, you will parallel more filters. The "more to it" part is having to calculate the passive component values for the extra filters.

c12mech · 23rd March 2011, 02:39 AM

Would you happen to know where I could find the formulas for the needed calculations? This is the part I am stuck on.

C04pl · 23rd March 2011, 05:50 AM

Hi
It may be not so easy to add more filters. You may know what width of band all of these filters are. If its 6db/oct then changing some another close freq filter may also make changes with another - just they will so close each other. To make true graphic multiband eq will be better idea to find 12 or 18 or even 24 db/oct eq. You need band stop/notch filters to be not close enough to make changes in neighbor frequencies. For example there pot sliders: 32, 45, 60 Hz... then 45 can make changes in both 32 and 60 Hz. This will be really unwanted thing.
Cheers

stratus46 · 23rd March 2011, 07:09 AM

Quote:

Originally Posted by c12mech

Would you happen to know where I could find the formulas for the needed calculations? This is the part I am stuck on.

Those opamps are known as Gyrators. This calculator should help. Worked great when I re-tuned the bottom 2 stages of a 5 band graphic EQ in a Technics receiver. 80 and 320 Hz was ridiculous. 25 and 180 Hz suits me better.

Guitar Pedals: Gyrator Filter Calculator

G²

mickeymoose · 23rd March 2011, 01:16 PM

Go to Spectrum Analyzer and Equalizer Designs for more info. E

23rd March 2011, 01:23 AM	#1
c12mech diyAudio Member Join Date: Jun 2009 Location: GTMO	Adding bands to an equalizer circuit? If I were to build a 10 band EQ similar to this one: Graphic Equalizer Circuit for 10 Frequency Bands how would I make it a 20 band circuit? Is it just a matter of adding more of the same IC sections and components or is there more to it? I've looked around and don't seem to find a lot of info on building anything more than the 10 band EQ shown. I'm sure it is probably overkill but it is just something I want to try. Any help would be appreciated.

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23rd March 2011, 02:08 AM	#2
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio TX	Yes, you will parallel more filters. The "more to it" part is having to calculate the passive component values for the extra filters.

23rd March 2011, 02:39 AM	#3
c12mech diyAudio Member Join Date: Jun 2009 Location: GTMO	Would you happen to know where I could find the formulas for the needed calculations? This is the part I am stuck on.

23rd March 2011, 05:50 AM	#4
C04pl diyAudio Member Join Date: Mar 2011 Location: its NOT France	Hi It may be not so easy to add more filters. You may know what width of band all of these filters are. If its 6db/oct then changing some another close freq filter may also make changes with another - just they will so close each other. To make true graphic multiband eq will be better idea to find 12 or 18 or even 24 db/oct eq. You need band stop/notch filters to be not close enough to make changes in neighbor frequencies. For example there pot sliders: 32, 45, 60 Hz... then 45 can make changes in both 32 and 60 Hz. This will be really unwanted thing. Cheers

23rd March 2011, 01:16 PM	#6
mickeymoose diyAudio Member Join Date: Nov 2008	Go to Spectrum Analyzer and Equalizer Designs for more info. E

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