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Old 8th January 2006, 10:54 PM   #1
lineup is offline lineup  Sweden
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Smile LAB10 Audio Amplifier Project



This is an experimental and easy build audio amplifier.
You can make changes and improvements in several ways.
The possibilities are endless!

Amplifier Details in this PDF:
LAB10 Audio Amplifier
More info at this website:
http://www.engga.uwo.ca/ece241b/


Attachment shows the basic circuit for
LAB10 Audio Amplifier
Attached Images
File Type: png lab10-amp.png (36.4 KB, 2122 views)
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Old 9th January 2006, 08:13 AM   #2
jaycee is offline jaycee  United Kingdom
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The op-amp follower is a pretty common idea. They make quite good headphone amps too
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Old 10th January 2006, 11:02 AM   #3
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Default Re: LAB10 Audio Amplifier Project

Quote:
Originally posted by lineup
You can make changes and improvements in several ways.
The possibilities are endless!
.... sure! 741 as input stage isn't very exciting. LM358 is possibly even worse but almost every other opamp is better
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Old 10th January 2006, 02:34 PM   #4
baggins is offline baggins  United Kingdom
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Default op amps & darlingtons

I used to make guitar practice amps using 741,s into h/phones they worked great you could over drive them into clipping distortion for effects if you wanted.
There was a better alternative with 2 amps in the 8 leg package I think
it was a 1448 I used these to make a disco console coupled to 125
watt amplifier modules from greenweld electronics it all worked successfully they are simple and reliable devices.

regarding Darlingtons Sony use them in multiples in the output stages of their home cinema amplifiers -Sanken 2448 & 1620
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Old 10th January 2006, 11:44 PM   #5
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The feedback of the op-amp should be connected to the output of the power amp.
No coupling caps (C1/C3) needed, and use a fet input op-amp, non inverting.
Some small changes to that circuit would make it perform better.
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Old 16th February 2006, 11:10 PM   #6
Bazukaz is offline Bazukaz  Lithuania
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Won't this amp run into thermal runaway ? I think emitter resistors are missing.
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Old 16th February 2006, 11:25 PM   #7
lineup is offline lineup  Sweden
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Quote:
Originally posted by Bazukaz
Won't this amp run into thermal runaway ? I think emitter resistors are missing.
In fact this is a true Class B amp.
there is no bias in output stage ( or very very little )

'bias voltage' is set by 3 diodes ~3x0.6 = 1.8 volt

but to turn two Darlingtons on, we need, more than 4 Base-Emitter drops

normal turn on for one darlington is something like 1.0V
in this case we need a bias voltage of ~ 2.0 volt to turn two darlingtons

So 3x0.6V = 1.8V is not enough
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Old 17th February 2006, 09:38 PM   #8
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Default Lovely amplifier Line up..thank you to show it to me

I love those simple circuits....this 741 is very famous, and was used since the seventies...it is nice.

thanks

Carlos
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Old 22nd February 2006, 03:34 PM   #9
rinox is offline rinox  Italy
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741 LF351: Jfet Input
Check the pinout, i think it' s not the same.
By the way, it's a good newbie project.
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Old 22nd February 2006, 03:41 PM   #10
lineup is offline lineup  Sweden
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Quote:
Originally posted by rinox
OP741, uA741
Check the pinout, i think it' s not the same.
By the way, it's a good newbie project.
Pinout is standard for single Op-amp.
+input - pin3
-input - pin2
+Volt - pin7
-Volt - pin4
Output - pin6

We should not use uA741 for audio anymore.

Good replacement for uA741 could be:
NE5534
TL071
OPA134
AD797
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