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Power Amplifier Solution

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darkatsuki12

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I would like to ask for assistance on how I can solve this circuits to understand how this works. Why the resistors have values like that.
 

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The .png file is huge. Can you make the view smaller
 

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Thankyou. The file size is now much better, especially for viewers using mobile devices or with slow/capped broadband.
There is no simple answer to your question. Resistor values are chosen according to the function of the relevant part of the circuit. In general, higher values are associated with low current parts and lower values with high current parts. Choice of value is often a compromise, bearing in mind such factors as circuit loading, thermal noise, gain, power loss, minimising battery current etc.
 
Thankyou. The file size is now much better, especially for viewers using mobile devices or with slow/capped broadband.
There is no simple answer to your question. Resistor values are chosen according to the function of the relevant part of the circuit. In general, higher values are associated with low current parts and lower values with high current parts. Choice of value is often a compromise, bearing in mind such factors as circuit loading, thermal noise, gain, power loss, minimising battery current etc.
Can you identify the the stages of this circuit?
 
Can you identify the the stages of this circuit?

Sorry, but explaining the workings of an entire power amplifier isn't something you can do in a forum post - and this design is a VERY old one, probably 1970's?.

It's pretty simple if you work at it though - you need to bear in mind the output stages are quasi-complementary darlingtons (as it was easier and cheaper to get NPN power transistors).
 
I agree with Nigel, The design is from an ERA where PNP technology wasn;t up to to speed with the NPN counterpart. PNP transistors used to be significantly more expensive than NPN's.

It's so much easier to make a fully complementary design. Search for "The Leach Amp". It's such an incredible design and I made a version back in the early 80's. It's totally complementary symmetry. So, much so, that I accidently made a mirror image of the board and after extensive troubleshooting, I WAS ABLE to use that board with two trace cuts. The input does consist of a differential amplifier front end too.

A rise time of 100 V.uS and an un-rolled off frequency response of 0 to 0.8 Megahertz is way overkill for an Audio Amplifier.
I compared it with a big name brand amp and the impact control of a 4 bx expander and the BIG amp choked on the input signal.

I also compared it with a Macintosh tube amp and Voice of the Therater speakers. These use Horns. The tube amp did much better handling the horns, They appeared louder and it also makes sense. The Leach AMP compared very well overall and excelled in the reproduction of bass. My friend said that this particular solid state amp would easily compete against the sound of a vacuum tube amp which I lot of us enjoy.

The usual method now is to include filters to roll off the high frequency response and to limit the response to DC. e.g. 0.5 Hz to 40 kHz.

The amp you describe is AC coupled and has some sort of phase splitter in the front end. There is a temperature compensated bias regulator, an ability to adjust the offset and a darlington output stage. The output is capacitive coupled and you really don't want that.
 
The amp you describe is AC coupled and has some sort of phase splitter in the front end. There is a temperature compensated bias regulator, an ability to adjust the offset and a darlington output stage. The output is capacitive coupled and you really don't want that.

Not a phase splitter at the front end :D

Capacitive coupling of the speaker isn't really any big deal, back in that era ALL amplifiers did it, and some of the best sounding amps ever made come from back then - and this circuit would probably sound pretty good.
 
I'm quite interested at what class this amplifier is? can anyone tell me?
It is an audio amplifier. If it operated in class-A then it would be a heater. If it operated in class-B or class-C then the distortion would be horrible.
This amplifier and most other audio amplifiers operate in class-AB.
 
This circuit brings back some memories as I built one very similar ( but simpler) in the mid 70's. The Circuit dates to the mid 60's. Sound is fine, but I don't have golden ears. T1 compares the input to the output and supplies a current proportional to this to T2, which amplifies it to drive the output thru the darlington pairs. C5 provides bootstrap drive to increase output swing. D1 won't give enough bias current feedback to prevent thermal runaway, and there are too many trim pots in general. Capacitive coupling the speakers is better for the home builder as you won't burn them up if the amp latches up. I decided I didn't need current limit in the bottom pair, so left that out.
 
Not practical to do that in a forum :(. See posts #4 and #6. Google for tutorials on electronics theory and amplifiers.
 
can anyone explain how this circuit works? what each part(transistor, resistor, etc) function as for the amplifier?
When you learn all about basic electronics then you will know what each part does simply by looking at the schematic.

I know nothing about a rocket ship so I do not know the function of each of its parts.
 
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