In article ,
"N_Cook" wrote:

Mark Zacharias wrote in message
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"N_Cook" wrote in message
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Mark Zacharias wrote in message
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"N_Cook" wrote in message
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My VN-900 has low level noise problems I have so far been unable to
resolve.
Coupling caps, power supply, signal transistors, no luck. Had to set it
aside for some future date...

Mark Z.


As far as intrusive noise.
Anyone know why +74V DC rail to a preamp ?

With bipolar transistors, the way to get low noise is to run low emitter
current. Low emitter current means high Rbe (intrinsic base resistance).
High Rbe means low gain (for gain determination, Rbe in in series with
the external emitter resistance). In that environment, one way to
recover some stage gain is to run a high collector resistor, and that
calls for a high rail voltage.

Isaac