AB100 Class AB Power Amplifier

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#883
Goodday all,

Guy's some help with this stupid question plse. Railvoltage is +-40V. Bias is 20mV, dc offset is 9mV. When I test with a sinus wave to clipping without load, the output goes to 28V RMS. Negative rail clips little bit before positive rail. Now, as soon as I connect a 7R load, the bias increases to 70mV, when testing for clipping with load, I only measure 15V RMS, that is only 30Watt. Transformer is big enough, can it be because the smoothing caps are only about 5000uf per rail ? That is only for initial testing, It will be 20 000uf per rail when all is done ? Or perhaps 1R emitter resistors or perhaps because only 1 pair OP transistors is installed. Why is the output so low ?Help will be appreciated.😕


Regards
Jan
 
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#888
This year it is very cold here, water pipes freezing, Water heaters bursting, the same as when I was young. The August winds started to blow as it should, so hopefully the summer season will be wet, it has been extremely dry here for a couple of years, farmers having a hard time. I love the Subaru cars, Flat boxer motors, distinct sound and very fast !🙂
 
#889
Had a chance to do some work today, one channel finished. Only have 5000uf per rail currently, I will connect some plenty more tomorrow and see how it sounds. DC offset 10mV and bias 20mV per emitter resistor.🙂
 

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#890
Looks good :violin: !
i got for free today nos (20 year old stock) daewoo electrical capacitors - 4700uf @ 35V - I charged 60 of them through a resistor - they hold charge well but still need to check them with ESR meter.
Looks like I'll have to build a Pass A class amplifier😀
 
#891
osscar, I have made a monstrosity mistake the other day, I have put 4 Nichicon capacitors on a power supply to see if they will reform. Actually there were nothing wrong, they were just 4 months on the shelf. Connected them with inverted polarity through 5K balancing resistors without noticing it. Checked them after 30 min and found they were warm, not hot. Tested them after discharging, their capacitance were down a LOT, decided to bin them. Stupid mistake it has been, just lucky I had no cleaning to do !😀 Fokus, man fokus !!😀
 
#892
osscar said:
Looks good :violin: !
i got for free today nos (20 year old stock) daewoo electrical capacitors - 4700uf @ 35V - I charged 60 of them through a resistor - they hold charge well but still need to check them with ESR meter.
Looks like I'll have to build a Pass A class amplifier😀
Click to expand...
osscar, Where you come from I think it gets very cold, so a class A amp will help to alleviate the cold😀. I have build a JLH oldskool amp with a single rail supply. Sounds really good but I needed more power. I you have very efficient speakers then it may work, but my kind of music needs a bit more!😉😀
 
#893
Thanks osscar and Mr Pass, both amps sounds good and it does have a tight bass that sounds superb !🙂 And none of the terrible oscillation that were predicted by Sakis. Sakis, plse build a channel, you will be surprised.😀

Regards
Jan
 

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#900
Hi mpmarino, I happen to have a spare pair of Nelson Pass boards. I had planned on building a few of these amps but have paired back to a single build. So I also have a full BOM of extra parts along with the boards if you're interested. Feel free to PM me.
 
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