3W Pure Class-A AMP

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DarkHorse

DarkHorse

Member
Joined 2005
#1
I design this Circuit Lastyear(2004)...
But Mr.Pass(Nelson Pass)had work it out as preamp in 1996...
God..
:smash:
Ok,let's see the Circuit:
 

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#9
PMA said:
Nice design 😉 . Please let us know your listening impressions. Maybe you are losing a little bit more power than necessary 😉
Click to expand...

hi,PMA:
the amp didn't work out yet!But trying my best now--buying electric device and its out shell ..etc
I hope the circuit will sounds good,my friend told me that can it compare with 2A3 vacuum tube amp..
in fact,I don't own both of them now..haha
same as you expect,I doing things for it!
have fun!


Circlotron said:
Darkhorse, this is one I made about 2- 1/2 years ago and is still going well. It uses a big choke instead of a resistor and so it has half the power loss than usual.

Circuit. http://www.diyaudio.com/forums/attachment.php?s=&postid=183394&stamp=1054194645

The complete thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=6338&perpage=50&highlight=&pagenumber=1
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hello,Circlotron:
I read your post thread "My first ever Class A amp",we almost have same idea of class-a amp form,yours is using inductance winding,the efficiency near to 50%...High!I saw the same idea in passlab.com, nelson pass new design zen-7,good idea..
but the high quality inductance is hard to DIY or buying!is it?
I don't want to change my mind-Use aluminium case power resistance,only this I can choose for this circuit..
and I hope it will sounds truly..
happy!
 
#10
I have make some change with the circuit..
now it don't need regulated power supply..
more high voltage supply,burning 67watte to get 4watte(RMS) output power!just like SOZ's hot..
see the update schematic diagram:
:smash:
 

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#11
Hi Darkhorse,

Please don't think that I am picking on you personally, but I so often see 'simple' circuits like these.

Yes (Post 10) will work, and it has simple internal ac and dc feedback, but ......... nobody ever seems to comment on the fact that the control of loudspeaker back emf is asymmetrical, and thus the amplifier's output is liable to become characterised by the crossover/loudspeaker combination much more than is the case with an output stage that is capable of *actively* conducting both positively and negatively.

For example there can be a hefty NFB controlled positive current flow via M1, but only the current due to (1 + 6.8 + speaker) ohms flowing negatively.


Cheers ........... Graham.
 
#12
Graham Maynard said:
Hi Darkhorse,

Please don't think that I am picking on you personally, but I so often see 'simple' circuits like these.

Yes (Post 10) will work, and it has simple internal ac and dc feedback, but ......... nobody ever seems to comment on the fact that the control of loudspeaker back emf is asymmetrical, and thus the amplifier's output is liable to become characterised by the crossover/loudspeaker combination much more than is the case with an output stage that is capable of *actively* conducting both positively and negatively.

For example there can be a hefty NFB controlled positive current flow via M1, but only the current due to (1 + 6.8 + speaker) ohms flowing negatively.


Cheers ........... Graham.
Click to expand...

hi,Graham Maynard :
that is realy matter what your said,I will be back tomorrow,
..sorry!haha..time to off duty now..
happy!
 
#14
PMA said:
The circuit shown may serve as a "starting point" of the newbie el. designer. After he sees all the design flaws and problems he may move to higher circuit league - in this case the attempt would be valuable.
Click to expand...

hello,PMA:
haha...your word is funny and exactly,I don't feel any unsuitable
in this schematic,but I know if the amp runs,it's result will make me know more about the true!I will kept trying..
regards,
WINCO



:smash:
 
#15
perhaps,this circuit form is more fit to be preamp or headphone amp..
it's too low efficiency,when as a power amplifier..
and it hard to using constant current source instead of resistor..
here is the schmatic (author is our master:Nelson Pass) which I got it from internet,the main circuit form same as mine,but it is a preamp circuit:
 

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#17
Upupa Epops said:
If you can easy to build amp, try PMA's " Mosfet follower ". Many positive references on this forum 😉 . Efficiency of this connection is more better.
Click to expand...
hello,Upupa Epops ,PMA:
I have checked "MOSFET FOLLOWER",but find nothing..Wowo..
can you do me a favour to show this thead where?

best regards,
WINCO



😕
 
#20
here I have draw a circuit same as PMA's,but it's not easy to
regulating the out point voltage to 1/2Ucc,maybe need a high power resistor to help..perhaps,I will build it next..
and I will not give up with"3W Pure Class-A AMP",very eager to
do something for it (lastest version is 4W)now..

:hot:
 

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