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Laszlo's Valve Output Stage with Lundahl transformer
Laszlo's Valve Output Stage with Lundahl transformer
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Old 2nd October 2010, 03:05 PM   #21
stelios is offline stelios
diyAudio Member
Join Date: Dec 2002
Location: London UK
Originally Posted by oshifis View Post
.. AC current is transformed down to 88.4 uA RMS. I measured about 64 mV on the secondary. From these two values one can calculate the load represented by the cathode input impedance. It gives 724 ohms. Since I connected 1.5 k parallel with the cathodes, the true cathode input impedance is 1.4 kohm.
err... how can this be : 724 Ohms || 1.5k Ohms = 1.4k Ohms ?
In my books it is: 496 Ohms.

Am I missing sth ?


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Old 4th October 2010, 12:12 PM   #22
lcsaszar is offline lcsaszar  Hungary
diyAudio Member
Join Date: Mar 2004
Location: Budapest, Hungary
Well, I think I was ambiguous. The input impedance of a SRPP cathode (upper or lower) alone would be 1.4k each, the resulting input impedance including the parallel load resistor is 724 ohms.
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