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In Reply to: RE: You may have made a mistake with your modelling posted by drlowmu on January 26, 2015 at 06:30:32
jeff,
forget thermal stress with push pull... Get rid of class AB operation.
B+ voltage / (1/2) output transformer impedance = idle current in mA for class A
use the math to get your lower disapation, but you have to work with the output transformers you have...b+ can be worked out... I like l-critical choke input for push pull since you can get away with 1-2 henries if you run enough current in the finals.
example... lets say a b+ voltage of 300 volts and an output transformer that is 5k ohm...
300/2500 = .12
120ma per tube for Class A, 36w disapation (roughly)
now if you want to try an L-critical choke, (the horror!),
lets assume 20mA for the driver stage for simple math...
300volts / 260ma (total for one channel)
1.15 henry choke.
I'm finding you need some real capacitance after the choke... like 200-300uF, or do multiple stages like you prefer and tweak values to avoid rining.
sim that up and give me your opinion.
ps - if there is a UL tap, look up e-linear... :)
Follow Ups:
'Get rid of class AB operation'
Find some ultralinear curves and you'll find it lends itself more to AB1 . Have a look at the Genelex/GEC datasheet for example . Audiomatica used to have some interesting UL data but the site now seems to be down
Al
,
Have Fun and Enjoy the Music
"Still Working the Problem"
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