AB100 Class AB Power Amplifier

Just to confirm - the major suppliers of TIP142 and 147 have all switched over to some version of the TO-247 package. On and ST use the std TO-247, and Fairchild has a strange one with an M3 thru-hole (they call it a TO-3P variant). On made the switch in July of last year. There are lots of other darlingtons that may be suitable as well - do a search at Digi-Key. The TIP142/147 are cheap and plentiful, but not necessarily the best parts around.
 
Official Court Jester
Joined 2003
Paid Member
I don't know, as I pay little attention to what's out there in Bipolars these
days .........
Those parts were chosen because I had stock courtesy of the boys at Adcom
and knew that the probable OEM used them.

:cool:

in other words - I gotch ya , suckers ! :rofl:

........... (that said, we just made a 10 year buy on the closeout of some
Toshiba's).
.......

:cool:

between brackets , that means - ( my Pa , one clever chap , he is )

:devily:
 
This won't be popular with all the fanboys but oh well, here goes. I apologize in advance.

How is it that all the really interesting class A amps (F5 F6) have one power output device per channel, but a quite dated looking AB amp has 8 per channel. All the while, a class A amp puts far more demands on the output device(s).

Also, these TIP parts are ancient and far from state of the art, or even interesting. They certainly don't comply at all with the NP simplicity, purity and elegance of design we have been enjoying.

Beggars cant be choosers. I know that. I was hoping for an interesting looking class AB amp with single or double Mosfet pair outputs. Something that leveraged what NP learned with all the class A stuff, but for AB. (see my other post)

If you are going to build a AB amp along these lines (AB100), I think you would be much better off just building the 555 as it probably outperforms this amp in every way, and it's a lot cleaner of a topology. To me, it's a much better NP design than this NP design. LOL.

I understand that NP is over AB. He's done with the sound of crossover distortion. He's been there, done that and he's not interested in circling back. That's cool.

All that said, I completely and totally appreciate what he's doing for us DIY folks. I also think he is the type that would appreciate honest feedback. I guess I'm about to find out.

:)
 
I look at the AB100 as an example of what is possible with inexpensive parts. You are probably right about the 555, but isn't it quite a bit more complex? I think the design goal of the AB100 was low cost, not high performance. As a design engineer you have to give the guy who signs the check what he wants. It's unclear what was not liked about this design.

On the number of output devices topic, that's what you have to do with bipolars. Although rated at 125W, they are only good for 45W at 50V and that's before temperature derating. MOSFETs don't have that problem.

The front end is almost identical to the A40. Not overly complex but a big bang for the buck.
 
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This won't be popular with all the fanboys but oh well, here goes. I apologize in advance.

How is it that all the really interesting class A amps (F5 F6) have one power output device per channel, but a quite dated looking AB amp has 8 per channel. All the while, a class A amp puts far more demands on the output device(s).

Also, these TIP parts are ancient and far from state of the art, or even interesting. They certainly don't comply at all with the NP simplicity, purity and elegance of design we have been enjoying.

It's quite clear that the design was for some pro audio maker where part cost and reliability were the most important factors.
If you use stronger devices, you can surely go with one or two pairs (per channel).

PS: I find my F3 very interesting with its many lovoltechs ;)
 
It's quite clear that the design was for some pro audio maker where part cost and reliability were the most important factors.

Exactly the issue. Who cares about that? We are all here for the cutting edge from The Master.

This amp looks almost exactly like every boiler plate AB amp from 1990. I "designed" one in college that looks almsot exactly like this, minus the protective circuits and TIP devices.

I'm looking for something interesting, and no I'm not smart enough to come up with it myself. Maybe I will just try to get the F5 into AB and see what that sounds like.
 

6L6

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Joined 2010
Paid Member
buzzforb said:
I am relieved to find i have no desire to buila Pass amp......finally.


That's not my take on this at all...

I just got a pair of NHT 2.5i speakers, and they can be passively bi-amped (so that it actually does something real) because the woofer has only a low-pass and the mid-bass plays with no high-pass, so it's not affected by the woofer amp...

Anyway, put a pot on the front of this amp (for level control) and it might make the perfect amp for the LF section of a speaker like that...

:D :D :D
 
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,



:cool:
There is an inadvertent missing ground symbol in your schematic at the junction of R2, R35 and C8; so as to bias Zener Z1. Best.