ruden Posted August 4, 2005 Report Share Posted August 4, 2005 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 ;) Quote Link to comment Share on other sites More sharing options...
steven Posted August 4, 2005 Report Share Posted August 4, 2005 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 Quote Link to comment Share on other sites More sharing options...
ante Posted August 4, 2005 Report Share Posted August 4, 2005 Hi Steven,I think your circuit looks much better for the purpose! Quote Link to comment Share on other sites More sharing options...
elect Posted August 5, 2005 Report Share Posted August 5, 2005 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. Quote Link to comment Share on other sites More sharing options...
audioguru Posted August 5, 2005 Report Share Posted August 5, 2005 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 Quote Link to comment Share on other sites More sharing options...
tikbalang Posted October 22, 2005 Report Share Posted October 22, 2005 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 Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 22, 2005 Report Share Posted October 22, 2005 Hi Ticklebang, ;DEasy, just join them like this: Quote Link to comment Share on other sites More sharing options...
Shahriar Posted October 23, 2005 Report Share Posted October 23, 2005 HiAudioguru 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? ThanXShahriar Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted October 23, 2005 Report Share Posted October 23, 2005 A voltage controlled amplifier is an analogue multiplier you can get ICs to do the job for you like the AD633. Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 23, 2005 Report Share Posted October 23, 2005 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 Quote Link to comment Share on other sites More sharing options...
tikbalang Posted November 14, 2005 Report Share Posted November 14, 2005 Q1,Q2,Q3,_____BC547 45V 100mA NPN TransistorsQ4___________BC337 45V 800mA NPN Transistorcan i replace Q4 with S9013 transistor? can i use 3v power supply without harming other components or ruining the output signal? thanks in advance. Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 14, 2005 Report Share Posted November 14, 2005 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. Quote Link to comment Share on other sites More sharing options...
tikbalang Posted November 14, 2005 Report Share Posted November 14, 2005 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. Quote Link to comment Share on other sites More sharing options...
tikbalang Posted November 17, 2005 Report Share Posted November 17, 2005 C3,C6___________1uF 63V Polyester or Ceramic Capacitorsok. 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? Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 17, 2005 Report Share Posted November 17, 2005 C3,C6___________1uF Quote Link to comment Share on other sites More sharing options...
tikbalang Posted January 22, 2006 Report Share Posted January 22, 2006 what if i use a .1uF instead of a 1uF nonpolar which is hard to find? Quote Link to comment Share on other sites More sharing options...
audioguru Posted January 22, 2006 Report Share Posted January 22, 2006 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. Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted January 25, 2006 Report Share Posted January 25, 2006 1uf non-polarised is a fairly common value, it's actually quite easy to get to get hold of. Quote Link to comment Share on other sites More sharing options...
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