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RE: CCS Mu output question

" But, can the Mu-output, on top of a 12ax7, drive 300b?"

It depends on the CCS.

Gary's CCS have much lower output Z from the "mu" output than just a simple pair of dn2450s in cascode.

I believe it all has to do with the value of the current set resistor.

By biasing the gates of the MosFets upward, the current set resistor can be (needs to be) made a larger value for the same set current.

This applies more feedback for the MosFets so the output impedance of the mu output is lower.

I'm not sure a 12ax7 would have a low enough drive impedance using the mu output of a simple pair of MosFets in cascode and I know the 12ax7 wouldn't have enough drive current to drive the Miller capacitance of a 300b no matter what.

Have Fun and Enjoy the Music
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