From holsen5629@aol.com Tue Nov 23 13:53:54 2004
Subject:XK-3 Tube Circuit

<<< Does anybody know if the tube circuit in the XK3 is a starved-plate
design or a high-voltage design? >>> << I don't know for certain, but I'm pretty
sure it is a starved plate circuit. >>

Not starved plate, the XK-3 has a separate +220 VDC source for the 12AX7s.
(If it were starved plate, the voltage would be lower, likely 50 volts or less.)
The tube circuit itself is fairly standard--regular RC coupling between the
triode sections with minimal negative feedback so it has a lot of gain. The
high and low frequencies are handled separately, which is why two tubes are
required. (And not for left and right channels, nor is it wired for cathode
follower outputs like someone suggested when the XK-3 was introduced.) Contact me
privately if you need more details so we don't bore everyone to death with
this stuff.

<< Both tube sockets are mounted on a printed circuit board and there are no
wires to the board or traces on it that would seem to be heavy enough for a
high voltage circuit. >>

Vacuum tube devices have used printed circuit boards for decades. It's the
current, not the voltage that determine the size of the traces. I haven't
measured the current draw of the XK-3's tube circuit but it can't be more than 6-7
milliamps total. (A very small amount, BTW.)

Harvey Olsen

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