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Old 7th August 2012, 11:57 AM   #1
Reno1 is offline Reno1  United Kingdom
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Default Tone Control Filter

Hi I have been playing with this tone control circuit to replace my baxandall tone control. This circuit is designed to cut the bass, mid and treble -26db and to boost them 6db. It works fine however, I want to raise the boost a bit higher than 6db (maybe 12db) so would like to know which resistors I would have to replace. Thanks for you time, any help is much appreciated
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Old 7th August 2012, 12:15 PM   #2
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The circuit is strange, I never saw none similar to this, but appears to me that increasing R19 and R35 would be a starting point.
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Old 7th August 2012, 01:58 PM   #3
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Reno1 View Post
This circuit is designed to cut the bass, mid and treble -26db and to boost them 6db.
Do you mean AFTER the level is elevated by the first opamp?

The first opamp already has around 47k/8k2=5.7=15.1dB of gain. The second opamp more or less cut both frequency ends and the third opamp notch the midrange.

So if you want more gain, instead of altering the gain of the second and third opamps you can also increase the gain of the first opamp, which is already high.

Strange, if not bad tone control design imo.
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Old 7th August 2012, 02:43 PM   #4
Reno1 is offline Reno1  United Kingdom
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Hi thanks for your response, I am happy with the 15db gain on the volume pot, but I just want to be able to boost the actual tone frequencies more than 6db thanks
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Old 7th August 2012, 06:24 PM   #5
Reno1 is offline Reno1  United Kingdom
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Anyone?
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Old 7th August 2012, 08:14 PM   #6
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Reno1 View Post
I am happy with the 15db gain on the volume pot, but I just want to be able to boost the actual tone frequencies more than 6db thanks
Oh so you want to boost above volume level...

This depends on the value of your pots. If the resistance on the left of the wiper equal to the resistance on the right, you get 0dB. So to increase gain what you want is to increase the pot (e.g. to 100K) or to lower R22, R17 and R25 to half of it (6k8-->3k3, 5k6-->2k7)
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Old 7th August 2012, 09:50 PM   #7
Reno1 is offline Reno1  United Kingdom
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Sorry I dont quit understand what you are saying, all I am trying to do is boost the individual frequencies above 6db, so I want to know which resistors to change without affecting the turnover frequency thanks
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Old 7th August 2012, 11:04 PM   #8
Jay is offline Jay  Indonesia
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Turnover frequency is determined by the RC networks, you don't want to change that. 330n (C10) determines the low frequency, 1n (C13) determines the high frequency and 47n (C14) determines the midrange frequency. See pic
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Old 7th August 2012, 11:16 PM   #9
Jay is offline Jay  Indonesia
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I think it is better to design the TC where you can control the pole frequencies ala parametric EQ. Here is a good one from www.sevenwoodsaudio.com
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Old 7th August 2012, 11:25 PM   #10
Reno1 is offline Reno1  United Kingdom
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Thanks for your time it is very much appreciated, I will make the following changes tomorrow and let you know how it turns out, thanks again
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