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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old Today, 09:25 PM   #17681
dreamth is online now dreamth  Romania
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Quote:
Originally Posted by john curl View Post
The transfer function (exponential) of the bipolar is worse than the fet with is (square law).
Except the subtreshold region where most of the manufacturers actually are using the fets for the very low tempco and current consumption.Many commercial phono amplifiers with fet transistors operate high transconductance transistors at less than 0.1ma and less than 1v VDS .
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Old Today, 09:27 PM   #17682
dreamth is online now dreamth  Romania
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Originally Posted by Zung View Post
Bipolars require an input cap.
and capacitors are counteracting the exponential law of bipolars with their own exponential charging law!
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Old Today, 09:55 PM   #17683
hhoyt is online now hhoyt  United States
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by RNMarsh View Post
I dont see any significant difference between bipolar and fet for audio. Neither for Noise nor harmonic-wise.

Both can give ultra low noise and both can have only 2H and 3H dominant in any modern topology. Maybe for phono cart and direct coupled there is some advantage to use fets. Like high Zin and low current thru cart. But thats all I can think of.
What else?

THx-RNMarsh
All else being equal, an FET input preamplifier is less susceptible to RFI. Of course proper RF low-pass filters at inputs and outputs fix this for bipolars as well...

Howie
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