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can LM 4663 connect with LM 386 to eliminate noise?

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elnino86

New Member
Dear all,

My idea is to connect LM386 and LM 4663 in order to eliminate noise.Will it work?



Thanks

Elnino Wesbo

"I learn theory from hardware design"
 

audioguru

Well-Known Member
Most Helpful Member
You cannot connect the two power amplifiers together. One or both will blow up.
The LM4663 is being discontinued. Maybe because it is noisy?

Where is the noise coming from?
 

elnino86

New Member
owh..if that is the case,luckily i didnt connect it yet.Thank!!Im designing a hearing aid..my idea is to use LM4663 as a main IC instead of LM386.Can you roughly comment my idea?
 

audioguru

Well-Known Member
Most Helpful Member
You don't use a stereo power amplifier (designed for speakers) in a hearing aid. You should use an IC designed to drive headphones.

Hearing aids use a special IC that works from a very low supply voltage at a very low current. You probably will not be able to buy the IC.
 

elnino86

New Member
but LM4663 can drive 32ohm headphones right?correct me if im wrong.My project's objective is to design a low cost circuitry which mean in the range $200.I end up with almost 15 journals relate to the hearing aid development and mostly they use class D power amplifier in their design.My task for now is to choose the right IC for my design.My earlier propose is LM 386,however it is so classic and i need something else similar.Someone from internet suggest me LM 4663 but im not familiar with class D power amplifier.Do you have any suggestion sir?Or do you want me to review more detail about my project?


Thanks

Elnino Wesbo

"I learn theory from hardware design"
 
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audioguru

Well-Known Member
Most Helpful Member
The LM4663 has two class-D speaker amplifiers (that waste battery power unless you turn them off) plus two class-AB headphones amplifiers. Aren't hearing aids mono not stereo?

You should select a mono headphones amplifier without power amplifiers.
Do you know how much power you need to drive a headphone?
 

elnino86

New Member
One of criterion to design the circuit is to drive at low voltage but 3-9 V is ok for me. Does LM4915 meet my criterion?However it only have 6dB fix gain.I need like 100dB gain.Is there
any audio IC's meet my criterion sir?Thank for the information.Really appreciate it!!
 
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audioguru

Well-Known Member
Most Helpful Member
The LM4915 package is extremely tiny like most modern ICs. You won't be able to solder it.

A voltage gain of 100dB is rediculous. It is 100,000 times.
5mV from a microphone will be amplified to 500V.
A voltage gain of 60dB (1000 times) is plenty.

Use an opamp as a preamp then use a TDA2822M as a power amp. The schematic of a power amp and its pcb design is in the datasheet for the TDA2822M.
Most deaf people need the treble audio frequencies boosted so maybe the preamp can do it.
 

elnino86

New Member
Thank you sir for your advice/comment.

I will select the best component within this 3 days.TDA2822M will in my study list sir.

Is there any IC's similiar to LM4663?Because i need compression circuit in my design which will control the volume and amplify the soft sound only.Im also need to implement T coil and speech filter in my design.Im currently reading on some digital volume control which only use low voltage.Any comment sir?
 

audioguru

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The LM4663 does not have compression. The old NE570, NE571 and NE572 were compressor ICs. I don't know if they are still made.
 

elnino86

New Member
Thank for the Information sir.I had look out for NE570.Probably i need to order it.Sir,i have a circuit design which i found from internet.

cir44.jpg (image)

My question is,do i able to implement this circuit practically?
 

audioguru

Well-Known Member
Most Helpful Member
Can't you buy a digital pot IC for the volume control instead of making one from many very old parts?
 

elnino86

New Member
Thanks you very much sir!!Your information help me a lot.Atleast Im 30% progress on my project.Thanx!!


My next question will be on my design circuit or on component selection(hopefully im not stuck on that part)!!!See you soon!!
 

audioguru

Well-Known Member
Most Helpful Member
The very old TTL logic ICs need a regulated 5V supply with a lot of current.
You will be making the oldest and biggest hearing aid ever made.
The circuit and battery will be huge.
 

elnino86

New Member
The very old TTL logic ICs need a regulated 5V supply with a lot of current.
You will be making the oldest and biggest hearing aid ever made.
The circuit and battery will be huge.

Haha thanks for the advice.Biggest hearing aid is not in my objective.:D


Component selection give me headache!!Need to choose proper electret condenser pre amp circuit,power amp..etc.

Here my component choice so far :

Electret Condenser Pre amp : TS971
Compression:NE570
Volume control : DS1669
Audio Power amp : TDA 2882M

Any comments?
 

audioguru

Well-Known Member
Most Helpful 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.
 

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.


Maybe im too "analog" in designing circuit:)

What is the different between linear volume control and logarithmic volume control?I mean in the way their perform?
From my understanding,volume control suppose to be linear.If we increase the volume,the output increase in time with volume.

Correct me if im wrong.
 

blueroomelectronics

Well-Known Member
Maybe im too "analog" in designing circuit:)

What is the different between linear volume control and logarithmic volume control?I mean in the way their perform?
From my understanding,volume control suppose to be linear.If we increase the volume,the output increase in time with volume.

Correct me if im wrong.

**broken link removed**
 
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