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11th November 2011, 05:29 PM
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#1 |
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diyAudio Member
Join Date: Nov 2011
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Design simple Stereo Audio Amplifier
Does any Know how to design simple Stereo Audio Amplifier(Pre-Amp+Tone Control+Output Stage) by using LM358 op-amp and (8 ohm Speaker) ,the circuit should be working with 4.5V (e.g. 3 AA batteries)...????
I designed several circuits but I got 2 much noise  I really need some help PLZ....one of the circuit that I built is show below(Op-Amp Audio Amplifier)... |
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11th November 2011, 07:49 PM
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#2 |
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diyAudio Member
Join Date: May 2007
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Two problems: too much voltage gain (x300), and a noisy signal reference due to thermal noise from the 1M resistors. Assuming a 20kHz bandwidth I calculate 5.4mV of noise at the output, which is likely to be audible.
Another possible issue is instability. RF oscillation sometimes shows itself as excessive audio noise. |
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13th November 2011, 11:33 PM
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#3 |
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diyAudio Member
Join Date: Nov 2011
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I'm experimenting this circuit but unfortunately,i'm still facing these problems....
any suggestion with some details to how reduce excessive audio noise....any help, I will appreciate it..http://www.diyaudio.com/forums/attac...er-circuit.jpg |
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1st December 2011, 06:07 AM
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#5 |
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diyAudio Member
Join Date: May 2004
Location: Vancouver Island
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The easiest level meter is to use an LED driver chip like the LM3915 or LM3916. There are probably others that were more optimized for consumer electronics, but they may be obsolete now that everything is digital. Take a look inside scrap cassette players.
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1st December 2011, 06:41 AM
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#6 |
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diyAudio Member
Join Date: Mar 2011
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All resistors carry <a href="http://www.physics.ucdavis.edu/xdzhu/Physics122_2008/Johnson%20Noise%20Manual_2008.pdf">Johnson noise</a>. The higher the R value, the greater the noise. Your 1M resistors seem to be way high for normal outputs. You might also check the National Semiconductor <a href="http://www.national.com/ds/LM/LM158.pdf">datasheet</a> for your opamp for some ideas.
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1st December 2011, 12:38 PM
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#8 | |
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diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
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Quote:
Could this be another case of non declaration of student/pupil status?
__________________
regards Andrew T. |
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1st December 2011, 03:52 PM
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#9 |
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diyAudio Member
Join Date: Nov 2011
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Because for my experiment there are specifications for using some components,the list of the component that I can use to design the volume meter circuit : Transistors, Resistors,LEDs,Capacitors and AA batteries>4.5 volts.
So if any one can help me and provide schematic diagram I will appreciated..  Many thanks.... |
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