how do i change the centre freq from 12k to 6k
thanks ♪reg♪

 

What makes you think centre frequency is 12KHz?

 

What makes you think centre frequency is 12KHz?

The TL072's input does not go to the minus rail so doesn't your circuit need a minus supply voltage?

 

What makes you think a treble control would have a centre frequency? Treble controls are normally shelving filters.

 

The TL072's input does not go to the minus rail so doesn't your circuit need a minus supply voltage?

sorry for omitting . . the rails are 17-0-17
so how can i change the shelving to 6k

 

The TL072's input does not go to the minus rail so doesn't your circuit need a minus supply voltage?

Yeah, just figured that myself... wasn't happy with that sweep... this is better.... rail voltages, as long as big enough, don't affect AC sweep

Anyway, what was it you want to change? Pot in centre = 0dB impact, at end its +/-14dB @ 40KHz approx



Yeah, I know it says +/-5v on the net names and 17v on the sources....

 

Assuming you meant for the pot to have a bigger impact at lower frequencies, changing C1/C2 t0 15n and R2/R3 to 10k and 12k pulls the response to the control nearer 8 - 10kHz at the ends without too much impact on the centre.

 

i want the treble pot to boost or attenuate at 6k ( appx )
thanks
♪reg♪

 

rail voltages, as long as big enough, don't affect AC sweep

The AC sweep uses a linear model so doesn't care what the supply voltages are.
The supply voltages are to set the bias point where the linear models are calculated.

Note that if you use 1V for the AC input, then the output will be in dB gain or attenuation with 0dB equal to a gain of 1.

 

i want the treble pot to boost or attenuate at 6k ( appx )
thanks
♪reg♪

But what do you want to happen between 10kHz and 20kHz?
If those frequencies should be left alone, then what you have is a mid-range control.
If those frequencies should also be boosted/attenuated, then the standard Baxendall circuit will do the job.

 

But what do you want to happen between 10kHz and 20kHz?
If those frequencies should be left alone, then what you have is a mid-range control.
If those frequencies should also be boosted/attenuated, then the standard Baxendall circuit will do the job.

this is part of a parameteric eq consisting of treble/hi mid/lo mid /bass
the only useful frequencies for this situation are 40-6k
the hi mid covers 600 to 10k
but i might want to cut at 1k but boost at 6k ? boosting at 12k has no relevance or advantages ??
ie at 12k the treble pot is redundant

 

The opamp circuit shown in post #6 will not work since its inputs are biased wrong.
The circuit in post #7 is a treble tone control circuit.

You described wanting a 4 bands EQ boost and cut circuit which is different.
Then you need a hi-mid and a lo-mid bandpass filters and a treble and bass tone controls filters.

Audio reaches to 20kHz. If you make a bandpass filter at 6kHz then all the high frequencies above 6k are gone like in an old telephone or an old AM radio. Maybe you need hearing aids to hear high frequencies.

I am old and deaf to high audio frequencies above 1kHz. My hearing aids boost high frequencies then I hear almost like when I was young.
The hearing aids also have features like noise reduction, compression for very loud sounds and directionality.

 

The opamp circuit shown in post #6 will not work since its inputs are biased wrong.
The circuit in post #7 is a treble tone control circuit.

You described wanting a 4 bands EQ boost and cut circuit which is different.
Then you need a hi-mid and a lo-mid bandpass filters and a treble and bass tone controls filters.

Audio reaches to 20kHz. If you make a bandpass filter at 6kHz then all the high frequencies above 6k are gone like in an old telephone or an old AM radio. Maybe you need hearing aids to hear high frequencies.

I am old and deaf to high audio frequencies above 1kHz. My hearing aids boost high frequencies then I hear almost like when I was young.
The hearing aids also have features like noise reduction, compression for very loud sounds and directionality.

i dont need freq above 6k + hearing freq below 6k does not make them 'telephone like'
telephone sound alike is a very narrow band ie 1k/2k (or whatever) no bass no treble
an earing aid is of no use whatsoever when trying to analyse audio as is

 

i dont need freq above 6k + hearing freq below 6k does not make them 'telephone like'
telephone sound alike is a very narrow band ie 1k/2k (or whatever) no bass no treble
an earing aid is of no use whatsoever when trying to analyse audio as is

i dont need freq above 6k + hearing freq below 6k does not make them 'telephone like'
telephone sound alike is a very narrow band ie 1k/2k (or whatever) no bass no treble
an earing aid is of no use whatsoever when trying to analyse audio as is
audio stretches way beyond 20k but if youcan hear a 20k tone then you have good hearing
The hearing range for the average across the board is 2k to 22k depending on age etc
so the requirements of the discussion is to address the issue not the failing of peoples abilities
♪reg♪

 

freq below 6k does not make them 'telephone like'
telephone sound alike is a very narrow band ie 1k/2k (or whatever) no bass no treble

Not quite. The “old” analog telephone frequency range is 300Hz to 3.4KHz (more than 1k/2k). Limiting audio below 6K is closer to telephone-like than full voice. The human voice ranges from 100Hz to 17KHz. Almost three times a 6KHz range.

So I agree with Audioguru. That filter will result in poor sound - unless that’s what you’re after.

 

Normal hearing is from 20Hz to 20kHz. Old men and people who played with guns and noisy construction equipment have poor high frequency hearing. I guess few women play with guns and construction equipment.

1) A very simple and cheap equalizer has only bass and treble shelving controls.
2) A simple one like you have has bass, lo mid, hi mid and treble. The bass and treble are shelving.
3) A simple equalizer for a car audio system has 5 or 7 frequency controls.
4) A good equalizer for a home audio system has 10 controls for each audio octave.
5) A professional equalizer has 31 third-octave controls.

You can change your 12kHz shelving treble control to 6kHz but then you should also reduce the hi mid frequency band.

 

At my job, I worked with audio systems and telephone systems. Conference call customers complained about the muffed telephone voices so I made an equalizer that boosted from 2.5kHz and higher. Every demo I made was sold.

I called out on one telephone line then answered the next line. I made a measurement of the round trip frequency response. It cut frequencies above 2kHz.
I complained to Bell and they said it was normal. If the response at 3kHz was worse than -10dB then they might boost it.

Polycom makes a wideband telephone conferencing system that uses two telephone lines and frequency converting, to double the high frequency cutoff.
Today, AM radio stations boost high audio frequencies.

 

There's also parametric equalizers, where the centre frequency, bandwidth, and boost/cut are all adjustable. You can make those from a state-variable filter, with a single quad op-amp per channel. State-variable can also give high and low-pass.
https://sound-au.com/articles/state-variable.htm

 

thats for the info
i change the 4n7 caps to 10n and the shelving dropped to nearer 6k ( i checked with a sweep sinewave osc )
i dont know what the slope is i cant plot it . . The circuit is part of a parametric eq with bass / lo mid(sweepable) / hi mid(sweepable) and treble
it is used just for guitar so 12k shelving is redundant for me
the circuit runs at 17-0-17 and is part of a legacy soundcraft delta studio mixer input channel
thanks again for all the advice
♪reg♪