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RE: Buffer Circuit for Passive Preamp - Questions

68.36.161.38

In Reply to: RE: Buffer Circuit for Passive Preamp - Questions posted by Mike C on May 10, 2008 at 02:24:33

Mike,
What poor drawing?
The biasing arrangement in circuit B is the same as it would be, if the parts were rearranged into common cathode topology. Circuit B is self (cathode) biased. RC is the bias set part and RD is the load part. Circuit A is fixed bias.
You can eliminate the I/P cap., if you use a bipolar PSU. Simply connect the grid resistor to ground. A 40 V. negative rail is quite sufficient, when SS CCS loading is employed. You will need a "taller" negative rail to use a pentode as the current sink. Ground g2 and connect g1 to B-. A trim pot. in the line between cathode and B- sets the "idle" current.
Eli D.

Edits: 05/10/08

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Many Thanks - Mike C 07:55:28 05/10/08 (0)

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