by EWBrown » Tue Sep 23, 2008 12:17 pm
One major risk with grid chokes is that they are very susceptible to picking up 60Hz magnetic fields from the power trannie or filter choke(s). Some serious mu-metal shielding is usually necessary, especially when everything is pretty close together on a compact chassis.
The high-inductance grid chokes are better applied to SET designs than for PP, anyway, and are probably best used with "fixed" grid bias. Needless to say, any grid current can cause additional serious problems, including blown chokes, the 3200H winding uses very thin gage wire (like human hair) which does not tolerate current (even an mA or two is too much).
/ed B
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