Marshall JVM Cold Clipper Plate Bypass

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Gregr
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Marshall JVM Cold Clipper Plate Bypass

Post by Gregr » Sun Apr 03, 2022 10:22 pm

I’ve been working out a few ideas for modding a DSL. I really love the JVM OD1 Orange and Crunch Orange modes and would like to implement it as closely as the rest of the circuit will allow.

The third gain stage of the JVM has a 10k cathode resistor and has 100k of resistance connecting the plate to the supply rail. In Orange mode 82k of this resistance is AC bypassed with a 1uF cap with 22k connected between the bypass cap and the plate. The output of the gain stage is taken off the plate. The load off the plate is 22nF and 570k. I haven’t yet measured the plate voltage and haven’t attempted to draw a load line with the AC load, nor have I looked at a waveform on a scope.

Can anyone explain what is the effect of bypassing 82k?

I imagine that the signal still clips the same as it would without the 82k being bypassed (in the red modes) when the input signal swings low enough to stop the flow of current. I’d also wager to guess that the negative cycle at the output is attenuated resulting in a lower 2nd order spike.

Does this make any sense, or am I off the mark?

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