Amplified Ear help!!!!

[ruden]

I have copied the amplified ear.

http://www.electronics-lab.com/projects/audio/023/index.html.

Can someone explain this thing? How it woks?
I am really curios :-\ about this "constant volume" thing that a signal with high or low amplitude can be levelled at the same point....

Please....

Thank you

 

[steven2]

i biult the amplified ear to but it dident work so i changed 2 of the caps to electros and did a bypass job and it worked  but i got some feed back but if tou want something that will do ok look at the parabolic mike circuit  and electret mike preamplifier somewhere in the forums , well ill post the one im refering to here it dose ok in amplifieing sounds to like the amplified ear would but this ones easyer to biuld

View attachment 37435

 

[ante1]

Hi Steven,

I think your circuit looks much better for the purpose!

 

[elect1]

Hi to all, I think too that Steven's curcit is better (it's easier to build), but it doesn't seem that it have a logarimic amplifier. It will increase hi signals with same coefficient as low signal and it will be to noisy.
If I am not wrong in first circuit exist the modul for logaritmic amplifing (in red quad). It amplifing low signals more then hi signals and in output all signals will be approximate of same intesity (("constant volume) 4 ruden).
This cind of amlifier is frequently used in radar curcit so dot in catode its same intensity for objects far of radar antenna as for clouse ojects.

View attachment 37436

 

[audioguru2]

Hi DRulje,
Q4 is just an ordinary amplifier.
Q1's gain is controlled by its base current. With a low input sound level, R7 in series with R2 provides plenty of base current to Q1 and it has plenty of gain. Q2 amplifies the output of Q1 so that when a signal level is high enough at the output of Q2 to cause Q3 to turn on, then Q3 conducts.
With Q3 conducting , it and R6 in series with it make a voltage divider with R7, reducing the base bias current of Q1 and reducing its gain. C4 filters the DC gain control voltage and R2 converts the voltage into a current ;D

View attachment 37439

 

[tikbalang]

how can the amplified ear circuit be coupled to this fm transmitter? what modifications will be needed?

http://tacashi.tripod.com/elctrncs/smplfmtr/smplfmtr.htm

View attachment 37841

 

[audioguru2]

Hi Ticklebang, ;D
Easy, just join them like this:

View attachment 37842

 

[Shahriar]

Hi
Audioguru explained the circuit perfectly.
In Communication circuit this is Called AGC(automatic Gain control). the best example of this circuit is in TV Tuners. when a TV receives high power, the AGC amplifies the signal a little and when received power is LOW the AGC Increases the Amplifier Gain.

In the main circuit C3 and D1 creat the Clamper circuit which shifts up all negative signal above zero. Clamper are very useful circuits.

But Does anybody know how is it possible to design a DC controlled Amplifier with OpAmps?

ThanX
Shahriar

 

[Alun]

A voltage controlled amplifier is an analogue multiplier you can get ICs to do the job for you like the AD633.

 

[audioguru2]

I've used a FET as a voltage-controlled-attenuator.
I had a car radio with a cassette recorder that attenuated the signal with resistors then used an ordinary biased diode as a current-controlled-attenuator. It sounded fine. ;D

 

[tikbalang]

Q1,Q2,Q3,_____BC547  45V 100mA NPN Transistors
Q4___________BC337  45V 800mA NPN Transistor

can i replace Q4 with S9013 transistor? can i use 3v power supply without harming other components or ruining the output signal? thanks in advance.

 

[audioguru2]

can i replace Q4 with S9013 transistor?

Yes.

can i use 3v power supply without harming other components or ruining the output signal?

Why? The project is designed for 1.5V. With 3V some of its biasing resistors need to be changed. The earphones and Q4 might be damaged.

 

[tikbalang]

the case i'm planning to put it in holds 2 aaa cells (cheap auto scan fm radio) and i want to preserve its authenticity. in that case, i will put in a series resistor and/or a small led. thanks audioguru.

 

[tikbalang]

C3,C6___________1uF  63V Polyester or Ceramic Capacitors

ok. i built it, and it didn't work. could it be because i used 1uF electrolytics for c3 and c6? when does one use electrolytic/polarized capacitors?

 

[audioguru2]

C3,C6___________1uF

 

[tikbalang]

what if i use a .1uF instead of a 1uF nonpolar which is hard to find?

 

[audioguru2]

what if i use a .1uF instead of a 1uF nonpolar which is hard to find?

Order the proper capacitor online.
With values that are 1/10th what they should be, the sound will be shrill without any low frequencies. It would sound like just a tweeter speaker.

 

[Alun]

1uf non-polarised is a fairly common value, it's actually quite easy to get to get hold of.