AB100 Class AB Power Amplifier

[Loudthud]

The missing ground should be at the C5, R35, R8 node just like the A40. Like Antoinel says, it's a bootstrap input to increase the input impedance.

 

[Loudthud]

Nelson, any words of wisdom on how to bias this thing? Also, why the 22 ohm resisitors on the base of each output transistor? Current sharing, stability, artistic license?

 

[Zen Mod]

they're 220R resistors

you can call them artistic stability supporters

😉

 

[Nelson Pass]

Also note that resistors are XXX plus multiplier: 1001 is 1K.

I like to quote myself. I find it elevates the tone of my conversation.

😎

 

[Gyuri]

Watch out Papa, this is already the first signs of a cult of personality.

Anyway, thanks for the clarification.

Gyuri

 

[Loudthud]

Also note that resistors are XXX plus multiplier: 1001 is 1K.

So a 221 ohm resistor should be 2210 like R10.

I'm finding that collector current needs to be about 50mA per transistor to smooth out the crossover region.

 

[georgescooo]

AB100 Amplifier - Micro Article by Nelson Pass
Since villagers armed with pitchforks and torches have begun camping out my front door demanding a Class AB power amplifier,
and Whereas, I am inclined to demonstrate my goodwill in this manner and do in fact have a 13 year old piece laying around unpublished

So it will be any article about AB100 published at "articles section" on FIRST WATT or Pass DIY? 🙂

 

[Zen Mod]

So a 221 ohm resistor should be 2210 like R10.
.......

221 = 22 x 10^1 = 22 x 10 = 220

or , just read them as 221R resistors

 

[Nelson Pass]

So it will be any article about AB100 published at "articles section" on FIRST WATT or Pass DIY? 🙂

You saw it already. It was a uArticle

😎

 

[Braun_]

Basic question. The original design produces 100W@8Ohms with 4 output pairs. If I want less power, around 25 to 50W, Can I just reduce the numbers of output transistors?
Thanks

 

[6L6]

If you only need 25W per channel, why not build a Class-A amplifier? Perhaps the F5 or F4?

 

[Zen Mod]

yup - one pair os OK , but two pairs more adequate (SOA , low impedance spks, yukyuk)

also decrease supply voltages

 

[Braun_]

If you only need 25W per channel, why not build a Class-A amplifier? Perhaps the F5 or F4?

Could sound strange, but I already have all the components needed for this project.🙂

 

[Loudthud]

WIth appropriate supply voltages I would suggest 1 pair for 25W @ 8 ohms, 2 pair for 50W @ 8 ohms. SOA is not very good with the specified transistors and can vary between manufacturers.

 

[oiphy]

from a fast glance... looks like this is available parts cheap on ebay... fakes or??

 

[6L6]

Has anybody looked at this and updated it to more modern (available) parts?

It's still an awfully interesting design... we shouldn't let it wither away.

 

[CanAm Man]

I like to quote myself. I find it elevates the tone of my conversation.

😎

(Doesn't quoting yourself create an echo, if you are fast enough?) 😀

 

[6L6]

(Doesn't quoting yourself create an echo, if you are fast enough?)

CanAm Man - As you once were one of the fastest guys on earth, wouldn't you know, or at least be able to comment on it?? 😀 😀 😀

🙂 🙂 🙂 🙂 🙂

 

[east electronics]

Is it ok if i quote my self also ? If so please let me know i would like to do that once or twice ....

 

[CanAm Man]

CanAm Man - As you once were one of the fastest guys on earth, wouldn't you know, or at least be able to comment on it?? 😀 😀 😀

🙂 🙂 🙂 🙂 🙂

Hard to say, Jim. We traveled so fast, the doppler shift made everything we said subaudible...! (Or that's my story, and I'm sticking to it--I can neither confirm nor deny, etc, etc, etc) 😉