Tone Control Filter

[reap461]

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 of the tone 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

 

[MrAl]

Hi,

Post a pic of your circuit and me or someone else will help.

 

[reap461]

Sorry I forgot to attach pic

 

[MrAl]

Hi again,


What are the values of the three pots, all the same too or different?
Also, are they all ganged or just two ganged or none ganged?
And what is the function of each one (treble boost, cut, base boost, cut, etc.)?

 

[reap461]

Anyone have any ideas?

 

[MrAl]

Hi,

You dont know what the pot values are? Can you measure them or something? How many controls are on this thing?
How did you determine you were getting -26db or whatever?

I guess one is bass, one treble, and one mid range?

 

[reap461]

Hi,

You dont know what the pot values are? Can you measure them or something? How many controls are on this thing?
How did you determine you were getting -26db or whatever?

I guess one is bass, one treble, and one mid range?

Hi the pot values are 20k the left IC2A is connected to the volume pot to give 15db gain. IC2B is for the bass R14 and for the treble R20 and the midrange is connected to IC3A which goes to the main out.

 

[audioguru]

People say that this Baxandall tone controls circuit works very well:

 

[reap461]

People say that this Baxandall tone controls circuit works very well:

Hi yeah I already have a standard baxandall circuit which I love, but I wanted to try something different. This circuit has a lovely sound, real smooth but I just want a bit more boost than 6db thanks for the suggestion

 

[audioguru]

Usually I don't use tone controls.
My sound source, amplifier and speakers sound like they are supposed to sound like.

Except I boost the treble from my local TV station when they try to hide the announcer's microphone under a pillow (very muffled sound).
They don't care about normal sounds. Instead the microphone must NEVER be seen.

 

[ronv]

Try R15 7.5K, C10 680n.

 

[MrAl]

Hi,

That's all he wants is more bass boost?

 

[reap461]

Hi I want more bass, mid and treble boost as its limited to 6db I have been playing with the circuit and decreased r22 and that gave me more treble boost im just trying to figure out the rest.

 

[MrAl]

Hi,

Use two of these circuits in series one after the other without the first gain stage
That will give you more controls too unless you gang them

Would you be happy to have just more boost if you could trade off for some of the cut? So the bass would boost more but not cut as much anymore.

What seems to help is:
Reduce R15 to 10k or so.
Reduce R22 to half it's value.
Remove R23.
Add resistor between the right side of R20 and the output of the op amp. Perhaps 2k
You may also want to increase C10 to get a more even bass boost down to the lowest frequencies.

We'd then have to work on the midrange, but see if that is good enough so far.

I havent done a complete analysis of this circuit yet.

 

[reap461]

yeah that would be fine

 

[flat5]

Hello AudioGuru. When listening to classical music late at night I hate that the announcers use bass boost and are loud. Tasteless!
In you post #8 can r2 be used as a volume control? If so, what value pot would you suggest. Thank you.

 

[audioguru]

Hello AudioGuru. When listening to classical music late at night I hate that the announcers use bass boost and are loud. Tasteless!
In you post #8 can R2 be used as a volume control? If so, what value pot would you suggest. Thank you.

R2 can be a gain control but not a volume control.
A 10k or 20k audio-taper volume control can be added to the input side of C1.

 

[ronv]

You can make it pretty flat with various cut settings which will give the same impression as more boost once you turn the volume back up. Makes me think the sound you like is louder.
Maybe a loudness control is what you are after.

https://www.redcircuits.com/Page67.htm

 

[MrAl]

yeah that would be fine

Hi again,


Here are some results for the first half of the circuit which reflects the bass and treble. If you think this is good we can go from there.
I managed to get the first half of the circuit into pure equation form so i can analyze the response for any combination of resistors or any frequency in a matter of less than a second each, over three or more pot settings for each pot. So if you have a certain set of resistor values you'd like to try just post the values here and i can run the equations. You'll get output data for various pot settings.
I suppose i could turn the equations into an interactive Windows program, but that's going to have to wait.

The following data is organized with all the resistor values first, then a table that shows the frequency response for two different frequencies 45Hz and 10kHz, which are most interesting, and that data is shown for three different settings of both pots as indicated, where each pot (one side) is set to either 0k, 10k, or 20k, as shown. The gain is then shown in db to the far right.

The first data set is with all resistors at their current values, that is, unchanged.
The second set is with some resistor value changes which show a boost in gain for both bass and treble, but some loss of cut for the bass.
Check these out and see if they look good. If you think they are what you want, try them and see how you like the sound.

The data:

FIRST SET:
R13=100000
R15=27000
R16=27000
R17=6800
R18=3900
R19=100000
R21=2700
R22=6800
R23=3300

TREB     BASS
R20a= 0  R14a= 0  freq=    45    -7.5 dB
R20a=10  R14a= 0  freq=    45    -8.1 dB
R20a=20  R14a= 0  freq=    45    -8.2 dB
R20a= 0  R14a=10  freq=    45    15.4 dB
R20a=10  R14a=10  freq=    45    15.4 dB
R20a=20  R14a=10  freq=    45    15.4 dB
R20a= 0  R14a=20  freq=    45    21.9 dB
R20a=10  R14a=20  freq=    45    21.9 dB
R20a=20  R14a=20  freq=    45    21.9 dB
R20a= 0  R14a= 0  freq= 10000    -1.7 dB
R20a=10  R14a= 0  freq= 10000    15.7 dB
R20a=20  R14a= 0  freq= 10000    22.3 dB
R20a= 0  R14a=10  freq= 10000    -1.3 dB
R20a=10  R14a=10  freq= 10000    15.7 dB
R20a=20  R14a=10  freq= 10000    22.4 dB
R20a= 0  R14a=20  freq= 10000    -1.2 dB
R20a=10  R14a=20  freq= 10000    15.7 dB
R20a=20  R14a=20  freq= 10000    22.4 dB


NEXT SET:
R13=110000
R15=32400
R16=54000
R17=6800
R18=3900
R19=100000
R21=2700
R22=3400
R23=3300

TREB     BASS
R20a= 0  R14a= 0  freq=    45    -0.5 dB
R20a=10  R14a= 0  freq=    45     0.4 dB
R20a=20  R14a= 0  freq=    45     0.6 dB
R20a= 0  R14a=10  freq=    45    17.1 dB
R20a=10  R14a=10  freq=    45    17.3 dB
R20a=20  R14a=10  freq=    45    17.3 dB
R20a= 0  R14a=20  freq=    45    26.3 dB
R20a=10  R14a=20  freq=    45    26.8 dB
R20a=20  R14a=20  freq=    45    27.0 dB
R20a= 0  R14a= 0  freq= 10000    -1.5 dB
R20a=10  R14a= 0  freq= 10000    19.1 dB
R20a=20  R14a= 0  freq= 10000    26.7 dB
R20a= 0  R14a=10  freq= 10000    -1.2 dB
R20a=10  R14a=10  freq= 10000    19.1 dB
R20a=20  R14a=10  freq= 10000    26.8 dB
R20a= 0  R14a=20  freq= 10000    -1.1 dB
R20a=10  R14a=20  freq= 10000    19.1 dB
R20a=20  R14a=20  freq= 10000    26.8 dB

 

[reap461]

This is great, and very much appreciated so many variables to play with