AB100 Class AB Power Amplifier

I experienced some humming from my freshly built M2X, can't determine if i had ground loop induced hum or transformer induced hum. So i did the followings...
Shifting my left channel heatsink block around while keeping the right channel where it should be.

I have to block the left channel with a iron chassis and even at an angle to the power supply board/transformer, to finally get a totally quiet left channel.

I now think that i may have to make partitions in the chassis that i m going to fit my M2X into, other than using Mumetal cover for the Edcor trans.

hum.jpg



I will try twisting those transformer secondary output cables next.
 
Last edited:
I've been listening to AB100 for two years now - I remember the day when I finished it (at that time I had serious health problems and depressed mood - but the hobby and soldering iron did not let me fall into depression). AB100 still it sounds so good!
Do other ab100 builders have any news and construction progress?
Happy listening!
 
  • Like
Reactions: 1 user
I've been listening to AB100 for two years now - I remember the day when I finished it (at that time I had serious health problems and depressed mood - but the hobby and soldering iron did not let me fall into depression). AB100 still it sounds so good!
Do other ab100 builders have any news and construction progress?
Happy listening!

Testing my AB100 now. I'll let you know the outcome :D
 

Attachments

  • 20190421_143211.jpg
    20190421_143211.jpg
    136.8 KB · Views: 1,007
  • 20190421_143213.jpg
    20190421_143213.jpg
    135.5 KB · Views: 1,011
  • 20190421_143236.jpg
    20190421_143236.jpg
    138.6 KB · Views: 962
  • 20190525_102437.jpg
    20190525_102437.jpg
    156.7 KB · Views: 956
Last edited:
Is the air coil also in the original schematic?
We never see that in class A designs?
Is it at the output? ….for stability reasons?
Is the air coil also in the original schematic? No i added it.
We never see that in class A designs? This is a class AB amp.
Is it at the output? ….for stability reasons? Yes in parallel with resistor. Provides stability when the amplifier is loaded with capacitive loads. See D.Self's ISBN 978-0-240-52613-3 book for a comprehensive explanation.
 
Thank you! I have ordered the book.
I know it is a class AB design. I have wondered why such a choke is never used in the Pass class A designs we see most of in this forum. I assume it is an advantage of class A that the higher bias makes the amp more stable in capacitive loads. I can probably read more about this when I get the book! …..the paperback version!


In cheaper class AB amps….I think the choke is always there…..as I remember from looking inside.
 
I still have a book from when I studied: Millman and Halkias, Integrated Electronics. I remember the teacher said that this book we should keep as we would use it later as a "lookup book". Maybe he was right. It is not at "amp level"......but much lower…..like "holes / electrons", PN-junctions etc. Maybe if this book is understood 110%......the other book is not needed :)
 
  • Like
Reactions: 1 user