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Home Projects Audio Motorola Hi-Fi power amplifier

 
 

Motorola Hi-Fi power amplifier
author:
Jacint Chapo


This is a very simple, low cost, Hi-Fi quality power amplifier. You can build it 5 ways, like its shown in the table (from 20 W to 80 W RMS).

 

Some comments:
- The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or . If their disagreement is bigger than 30 %, the amplifier would not give a clear sound. I used MJ3001 and MJ2501 transistors, and this disagreement was around 5%.
- Before the first turning on you must short circuit the inputs of the amp, and put a mA-meter on the output, than turn the amplifier on, and tune the R13 pot, to decrease the DC current on the output, to some uA-s, or in a lucky situation to zero. I was able to decrease it to 10 uA.

 

 

I am very contented with this amplifier. It gives a very good sound quality.
Have fun with it!


Jacint Chapo
6. 5. 2005.

 

Download this project in .doc format

 

 
 

 
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