The input of the amp is swamped with a 50 ohm dummy load capable of
dissapating 100 w. I made up my own using sixty(!) 3,000 ohm 2 watt
resistors in parallel. It is only the size of a coffee mug and works great.
I also use a 5 db T pad after the swamping resistor because the amp is so
easy to drive.
The input circuit is simple. A 1,000 ohm, 2 w. resistor goes to ground
across the input. The grids are fed directly through a .01 mfd capacitor.
Right at the grids are two 2.2 ohm 1/2 watt resistors in parallel for each
tube. (Effectively feeding each grid through its own 1.1 ohm 1 watt
resistor.) Bias is applied at the junction/feedpoint of the resistors.
Operating voltages and currents:
Ep = 2990
Max Ei per tube = 900 ma
I cannot measure the grid current at present but I can tell you that the
overload is not kicking out, so I assume I am not drawing grid current in
the
AB1 setting.
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