Power amp under development

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#3,102
😱 yeah ,mrrocky makes a good layout. I assumed Quasor
would work , it is classic "blameless" with cool mods.
the design would require matched LTP with no offset adjust,
but CCS would make for super low PSRR ..
(I use this, very superior)



That transformer is strange ..never seen one like that! 😀
 
#3,107
I think DX has a thread about all of Dr.jagodic's amp's (quasor,etc).

But the quasor is relevant/similar to the nmos (isn't it -power amp
under development) and should be discussed and
dissected for improvement of the base design.

The quasi design is sound and will work but I have left
extra pads and "universalized" my NMOS boards to
accept any changes to OPS,CCS,drivers, etc .

So far I have modified quasi's amps to have better PSRR
,absolute clipping symmetry(using p and n channel),
better slew,etc.

The one mod that is interesting in the good doctor's design is
the use of FET as the VBE (Thermal coeff same as MOSfet outputs??)

BTW ,panda, quasor is post 3095
 
#3,109
Quasi

I'm having a strange problem. Its a two pair NMOS 350 with +/- 60Vdc. As I'm increasing the bias current using VR2, the current rises steadily upto about 20-25ma. At this point even a slight increase of the trimmer, the current jumps to 100-110 ma. It stays at this value even if the trimmer is reduced. Once I power down the whole thing (after reducing the trimmer) and re-start, the current is back down to about 15-20 ma. I've replaced T8, T9 and T10. I've even removed the MOSFETs in pairs and tried out one pair at a time. With one pair the current jumps to 50 ma from about 20-25 ma.

Hari
 
#3,113
Okay, I seem to have solved the problem😀 I disconnected the 0.068uF cap C12 and did the current adjustment and was able to set it pretty smoothly. Then I replaced the cap with a 0.047uF cap and found the current setting is holding well. Very strange - I checked the 0.068uF cap with a C meter and it is perfect. Also, my other module has a 0.068uF cap and it also is working ok.😕 I wonder what's going on?

Hari
 
#3,115
And some photo
 

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