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BRSHiFi 21st April 2012 04:25 PM

Op-amp tone stack
For a 3 band equalizer tone control circuit, where do you recommend I place the center frequencies for each band? What should I make the bandwidth for each control, aka the frequency range the bass, mid, and high boosts and cuts?

Tekko 21st April 2012 05:05 PM

Just google baxandall tone stack and you should find quite a few verieties of tone stacks.

BRSHiFi 21st April 2012 06:29 PM

Most of the baxandall results just show existing circuits. Worst of all they do not give information that answers my question.

This pdf is really helpful when it comes to designing narrow-octave equalizers, but I am just looking to do a three band equalizer for now.

For a 3 band equalizer, i simulated a circuit using gyrator band filters that have the following specs:

- Bass: Cutoff frequencies at 10Hz and 400Hz. Center frequency 63hZ.

- Mid: Cutoff frequencies at 400Hz and 5200Hz. Center frequency 1442hZ.

- Treble: Cutoff frequencies at 5200Hz and 30000Hz. Center frequency to be determined.

Do you feel this is a good design, or do you think I should place the center frequencies and cutoffs elsewhere?

Tekko 21st April 2012 06:56 PM

I've never dealt with tone controls.

Frank Berry 21st April 2012 06:58 PM

It's all about your preferences.
Typically, the bass and treble filters are of the 'shelving' variety rather than the bandpass variety.
Let your ears be your guide.

mickeymoose 21st April 2012 11:36 PM

What is the EQ for?
Take a piece of paper and show us on a graph (frequency vs. gain) what you want. E

sreten 22nd April 2012 02:01 AM


Search and you shall find. There is a relatively simple 5 band tone stack
based on the "Cello" recently posted, as well as simpler variants. Its all
been covered before, the ideal tone control is not remotely a new idea.

rgds, sreten.

Loudthud 22nd April 2012 02:06 AM

There is a three band version of the Baxandall you can find on the LF353 data sheet:

There was an example with equasions in an old National Applications book, but I haven't been able to track that down.

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