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can LM 4663 connect with LM 386 to eliminate noise?

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elnino86

New Member
You like old parts, don't you?
The old DS1669 digital pot is linear. A volume control is supposed to be logarithmic.
Maxim-IC have some logarithmic digital volume controls.


I found DS1666 has a good feature which cope with my criterion.However,im not clear by "digital" mean in the data sheet.

I mean,the chip select pin confuse me a little bit.Is DS1666 suppose to connect with micro controller or analog circuit will just fine with it?:confused:
 

blueroomelectronics

Well-Known Member
Looks like a couple of buttons is fine.
**broken link removed**
Of course pin 10 will be for analog input in your design.
 
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elnino86

New Member
Looks like a couple of buttons is fine.
**broken link removed**
Of course pin 10 will be for analog input in your design.


Thanks a lot sir(both of you).:) Need to check the price for DS1666 and DS1669.Hopefully it not cost me a lot.:)

Here my component choice so far :

Electret Condenser Pre amp : TS971/MAX4465
Compression:NE570
Volume control : DS1669/DS1666
Audio Power amp : TDA 2882M
Speech Filter : TLV2221
T coil.
 
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audioguru

Well-Known Member
Most Helpful Member
What will the speech filter do? Remove the very important high audio frequencies of consonants and remove realistic low frequencies?
We can hear from 20Hz to 20kHz. Our hearing doen't make everything sound like a 300Hz to 3kHz telephone.
 

blueroomelectronics

Well-Known Member
Modern hearing aids are programmable to fit the frequency response of the wearers ear. Could be a tiny DSP.
Wonder why the OP is building one? You'll never be able to make one as small as a professional aid. Why a digital volume control?
 

elnino86

New Member
What will the speech filter do? Remove the very important high audio frequencies of consonants and remove realistic low frequencies?
We can hear from 20Hz to 20kHz. Our hearing doen't make everything sound like a 300Hz to 3kHz telephone.


Shalom sir,

The purpose of my speech filter(idea) is to eliminate noise from signal containing speech and noise.I assume that the user doesnt want to hear background noise,and he/she activate the filter.It just a random idea sir.Correct me if im wrong.
 

elnino86

New Member
Modern hearing aids are programmable to fit the frequency response of the wearers ear. Could be a tiny DSP.
Wonder why the OP is building one? You'll never be able to make one as small as a professional aid. Why a digital volume control?


Im intend to designing a low cost,effective and high performance hearing aid system.Programmable hearing aid is very expensive which cost the patient around $900-$3000,depending on it technology and brand.

This is a project which i need to study the cases of hearing impaired and hardware design is a part of my project.:)

The design and analysis part is the most challenging part for me.

The purpose of the digital volume is to replace mechanical volume control.Actually I had design a hearing aid system early in my project(I design the hearing aid just using LM 386 and uni directional ECM but it just a demo kit which allow me to understand more the concept.:)

Im also looking for software to do analysis for my design in near future.Does MATLAB or Pspice are suitable for this?
 

audioguru

Well-Known Member
Most Helpful Member
Did hearing aids ever use vacuum tubes?
This one will have a similar size and weight.

Hearing aids have frequency equalization. This project should include it.
 

elnino86

New Member
Did hearing aids ever use vacuum tubes?
This one will have a similar size and weight.

That soooOoo old skool sir :D

Hearing aids have frequency equalization. This project should include it.

The frequency equalization require me to implement dsp chip,i guess.Im designing a high performance analog circuit.However, i found a journal which they design a hybrid analog digital hearing aid.They using a micro controller to control the analog circuit.Unfortunately,im just understand the concept but failed to catch the design.
 
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audioguru

Well-Known Member
Most Helpful Member
You can make an analog equalizer. One parametric adjustable frequency with adjustable Q for its bandwidth and adjustable boost should work pretty well.

A simple treble frequencies boost circuit will also work pretty well.

A second-order Sallen and Key lowpass filter with its Q set too high boosts the high audio frequencies peaking at a frequency close to its cutoff frequency.
 

elnino86

New Member
A simple treble frequencies boost circuit will also work pretty well.

Owwh..its consist of few passive component and op amp right?what kind of op amp usually use in treble frequencies boost circuit?:confused:


Regarding to sallen-key low pass filter,what is the advantage of the filter compare to others?
 

audioguru

Well-Known Member
Most Helpful Member
You can use any opamp that is low noise and has the power supply voltage range that you want.

A second order Sallen and Key filter can have equal component values and has a flat response then sharp cutoff (Butterworth) when its gain is 1.6 times. When its gain is greater than 3 then it oscillates. When its gain is between 1.6 and 3 then it has a peak near its cutoff frequency. The peak is equalization. The cutoff reduces noise (and important high audio frequencies which are the consonants of speech).
 

blueroomelectronics

Well-Known Member
Why are you building this? Is it a school project?
Even with modern small ICs and other components it will be about the size of a cell phone (if your skilled)
 

audioguru

Well-Known Member
Most Helpful Member
Maybe in his country, cell phones are still the size of a small car.
 

elnino86

New Member
Why are you building this? Is it a school project?
Even with modern small ICs and other components it will be about the size of a cell phone (if your skilled)

No sir,It is not school project.Im not at school anymore:)

As far as i concern, the size of hearing aids are depending on what features are include in the design.:)

For my case,size seems to be neglect now.The most thing i care now is my concept and theory behind it.:(

Hopefully i can finish all this within this 10 weeks including report.
:):(:):(
 
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