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Whereas, I am inclined to demonstrate my goodwill in this manner and do in fact have a 13 year old piece laying around unpublished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)