Motorola Hi-Fi power amplifier
This is a very simple, low cost, Hi-Fi quality power amplifier. You can build it 5 ways, like it’s shown in the table (from 20 W to 80 W RMS).
Some comments:
I am very contented with this amplifier.
It gives a very good sound quality.
- The first thing that you must do, is to measure the end transistors
(T3 and T4) amplifying coefficient, the hfe or в. 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.
Have fun with it!
Jacint Chapo
6. 5. 2005.
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Jackson Teneng-von D 2019-12-22 15:27:55 Hi, Thanks so much for the schematic and explanation. I have a question: 1- The data sheet states a maximum supply voltage of +- 18V. Why do make an option for voltages higher than +- 18V? e.g. in case of 80W/125W you state a supply voltage of +-22V 2- What would be the value for R13, before tuning to get a suitable value that would correspond to the said low uA in the output? [Reply] [Reply with quote] |
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jorge loarte 2015-02-07 00:51:14 I find very interesting the diagram I will also try to build sound quality if trubieran a diagram tone control to apply to this amplifier thank you very much your friend peru jorge loarte [Reply] [Reply with quote] |
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