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In the Forum: Melquiades Amplifier
In the Thread: Single-stage Melquiades vs. DHT amps

Post Subject: Options, options...Posted by floobydust on: 2/24/2009

Options are limited here... looking at the schematic, you're sorta pinned in by the biasing topology used. One typical method would be to use a resistor divider network at the input grid to the 6E6P. Problem is, this results in a huge bias offset. By my calculations, the current flow thru the 20K and 12.1K resistors from the input (referenced at zero volts) to the grid (referenced at -4.3 volts) is 134 micro-amps. This would result in a voltage drop of 53.85 volts across the 402K grid resistor to the bias supply. This makes it's messy for putting a voltage divider network in between the crossover and the grid. The other option is to move ahead of the crossover and place a divider network between the input and the crossover. This would yield a much smaller offset in the bias which you can adjust for.

Regards, KM

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