ef14 dummy load in u47???

[seavote]

can anyone here reveal what this entails? i've read it is one cap and one resistor. can anyone explain the theory behind this mod. .i'll be getting a beezneez K7 capsule. if i can learn  this mod i'd like to try adapting it (component values) to a different ,cheaper tube, and putting it in a u47 circuit w/cinemag CM-2461NiCo    any ideas, advice, welcome. thanks

 

[mad.ax]

As far as I understand, 'dummy load' does not refer to any 'official' biasing scheme. And this can lead to confusion...

I guess the 'one cap and one resistor' you've read about is the cathode bypass bias of the Wunder. It is just regular cathode bias as seen in many microphones schematics. Adjust to tube and to taste.

Now 'dummy load' is also often used about fixed bias schematics where the cathode is tied to the filament in order to emulate the U47/VF14 behavior. Like seen in this schemo:
http://twin-x.com/groupdiy/displayimage.php?pos=-2608
Another good example is Max's MK7:
http://www.groupdiy.com/index.php?topic=30124.0

The basic idea behind this is to build a voltage divider between the cathode resistor, and the filament resistor. Given that the current flowing through the filament is way higher than the current flowing through the tube, the bias voltage at the cathode remains constant.

Axel