On 4 May 2012 02:21, Manfred Mornhinweg <manfred@ludens.cl> wrote:
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"The basic point is this: Class B or class AB push-pull amps MUST, I
repeat _MUST_ have something that provides balance around a true center
point. It cannot work in pure differential mode, because each FET
conducts for half of each cycle, and is in high impedance during the
other half cycle. You cannot draw current between one transistor that is
on and another that is off! That's why balun or balbal type output
transformers only work correctly in conjunction with a bifiliar feed
choke that provides the center point."
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Manfred
Likely you are right. I used separate chokes as proposed by Freescale,
then tried the pseudo centre feed of the tube primary. Neither one was
better than the other. I had just reconfigured to feed the drains via a
bifilar choke when that moment of fatal instability occurred. A hiatus has
been reached. At least for now.
Bob, 5B4AGN
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