Circuit diagrams of class A audio amplifier

[darklord4]

I need to build a class A audio amplifier with the following specifications

Output power: (1,3,5) W output through an (4,8) Ω load
Frequency response: ± 0.5 dB from 100-15 kHz
Efficiency:efficiency greater than 30 % maximum (when the ouput is dc)



I dont have much idea regarding amps, any help appreciated, say a ckt diagram.
Any help appreciated

 

[IanP]

Re: class A Audio Amp

"Simple Class A Amplifier"
**broken link removed**
or:
https://www.elecfree.com/electronic/class-a-amplifier-by-transistor/
or:
"3- 5 Watt Class-A Audio Amplifier"
https://www.redcircuits.com/Page80.htm

Rgds,
IanP

 

[darklord4]

Re: class A Audio Amp

thanks for the above mentioned links

I need help understanding the ckt
mainly what help are the resistors R3, R6, R7, R9, R10
and capacitors C6 and C7

Added after 1 minutes:

https://obrazki.elektroda.pl/74_1216280321.gif


this is the link for the image

 

[IanP]

Re: class A Audio Amp

R3 provides dc bias for Q1 (from voltage divider R1/R2) ..
R6 (alone) dc feedback to Q1 ..
R6/R7/C6 ac negative feedback, where C6 just cuts off dc component ..
In other words, R6/R7 set the amplifier’s gain ..
R10 works like a fuse ..
R8/R9 set dc condition for the dynamic load based on Q2 ..
And that should be it ..
Rgds,
IanP

 

[darklord4]

Re: class A Audio Amp

Could you please elaborate on the role of R8, R9

Thanks

Added after 19 minutes:

also whats the exact role of Q2 and Q3

Q2 seemed to be somekind of a stable current source
Q3 seemed to provide more gain
is my reasoning correct?