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Old 11th Sep 2019, 4:02 pm   #15
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 5,396
Default Re: Cathode follower line out - best practice

You can. But there is little virtue in a low value of cathode resistor.

The lower it is, the harder the valve has to work. Consider if you got the DC conditions right to allow you to use 10Ω, then the voltage gain of the CF would be fairly low and although output impedance would be super-low (a bit less than 10Ω) the distortion would be rather higher.

Really, the cathode resistor needs to be high in comparison with 1/gm. Then the gain approaches 0.9 and distortion approaches zero.

Last edited by kalee20; 11th Sep 2019 at 4:15 pm. Reason: Last sentence added
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