thebugger

modified 7 years ago

Class A Amplifier

755

11:06:55

Following the Death Of Zen amplifier, I made a few modifications of my own and got this. The primary focus was to increase the ripple rejection, and to fix an issue that was not accounted in the original circuit. The bootstrap circuit creates a back-current, that the zener cannot filter, and the regulated rail for everything before the power stage was left not so well regulated after all. Also, I changed the driver stage with a differential amplifier, which should help with distortion a bit. Personal note is that I don't really like the design as a whole, because there is no temperature drift compensation, but the circuit is worth a look. 

 Anyway, these are the specs I got :

- Input sensitivity - 3Vm for full swing
- Av - 5.7
- Output Power - 36W
- Drawn Power - 113W 
- Efficiency - 32%, which is around the theoretical maximum for a non-transformer coupled class A amp. 
- Frequency response - 10Hz-50kHz at -3db
- THD+N - 0.01% at 36W/1kHz
- Ripple Rejection - -100dB 

*Made some further modifications. The specs may no longer apply correctly. Need to remeasure. 

published 7 years ago

hurz

7 years ago

You say "..., and to fix an issue that was not accounted in the original circuit." were is the original circuit from, Web Link?

thebugger

7 years ago

Death of Zen is the original circuit, already mentioned it

Voltransistor

7 years ago

Nice circuit! How do the bootstrap works? I never understand the bootstrap function in an op amp

abobaker

7 years ago

Thank you :) This post reminds me of my old days with EC. Nice circuit, learned something new.

kiani

7 years ago

@abobaker hi, long time no see.. Could you. Would you plz. Share with us what new thing you learnt from death of zen!? Thank you.

hurz

7 years ago

the death of Zen was propagated from tooo many people.

hurz

7 years ago

I guess you started somewere here in the middle were "Zen" became "Death of Zen" right? http://sound.whsites.net/project36.htm

kiani

7 years ago

Thank uou, for udeful informative link... But whst an ugly name to start the birth of an idea to call the death of another idea which gave rise to the born idea.

kiani

7 years ago

When "i" designed something l deliberately made it simpler than possible to find out the minimal requirement limit. That was not death of anything.and nothing and nobody died. If they do a mental test on people i honestly wonder. How many pass,, of course if we trust the health of the test maker in the first place,,

abobaker

7 years ago

@kiani hi, it's a subtle thing, just that I used to do bootstrapping in Class-A a little differently, and seeing it done like that made more sense to me. Also a sound.whsites link is always helpful thanks hurz ... I know it's not a new circuit or anything, just that I recently got used to EC as a fighting-comments platform

kiani

7 years ago

@ abobaker this had been going on for a long time,, forign nationas and Chinese and school kids have been targeted by a griup of (i think) fascists, bulleys, don'y know how to call them, we have no way to protect oursrlves on this EC comm. Ad there is no blocking facilities,, the people targetted can not fight back cause of language barrier and fear. The only way left for us was to go public. It is very upsetting. "i" am sorry, and any support is welcomed in any form. Thank you, also as is EC are just watching,,, despite appealingly to them publicaly,, it is the only way, left to go public. "i" was under attack cause someone @ lebuch started ordering me to remove my citcuits also he started attacking school kids for placing their homework for their teacher to mark before the next day... There is a gange,, anyway follow the news if interested. Nice to hesr frome you anyhow. Take it easy.

lenzrulz

7 years ago

@thebugger, love your work...👍

thebugger

7 years ago

Thanks guys :) Just had some spare time and tried some modifications.

thebugger

7 years ago

Anyway, someone had some trouble understanding bootstrap circuits. They're a passive components equivalent of a constant current source, but it works only for AC. They work by keeping the potential across a given resistor constant, by returning some of the AC back to the mid end of the resistor network. One of the resistors experiences a constant current effect, while the other creates a back current, that usually affects regulator circuits, as most are not designed to sink the back current. This is one of the issues I addressed. Anyway, bootstrap networks can easily become a positive feedback and some care must be taken when incorporating such a network into a circuit

sasa4250

7 years ago

strongly!

hurz

7 years ago

@thebugger what is your problem to make the web link public were your improvments are BASED on?

thebugger

7 years ago

Because you're lazy. Type Death of Zen in Google, and literally the first circuit you see in images - that's the one.

hurz

7 years ago

Im lazy? I already googled and posted a link. Now dont be lazy and say yes this is the web link i have based my improvments on. Or say no its this one " .... .... .... " why is this so complicated for you?

thebugger

7 years ago

Yes, that's it

hurz

7 years ago

you know my english is not perfect. "thats the link you mean" or "you are that lazy"? Sorry, if this/that sounds penerant.

thebugger

7 years ago

No, it's fine :). That's the one. I also made some extra modifications in a different article. Check it out guys, I'm even in for an idea for thermal current compensation for the output stage. http://everycircuit.com/circuit/4559562815569920

Davidhk18

1 year ago

If I'd use this scheme to build a diy class a amp will it work and not explode ot break my headset? 😅

add comment in editor