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Old 11th Sep 2019, 3:46 pm   #14
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 4,573
Default Re: Cathode follower line out - best practice

You can use a low value cathode resistor by lowering the anode voltage with an RC anode feed network. The cathode resistor just needs to be high enough to support the required audio signal and the anode voltage just enough to prevent the vale going into saturation.

From the ECC82 datasheet a suitable operating condition might be:

Not sure on your HT volts but if say 200V
Rfeed=(200-85)/0.002 = 56K

When I had a similar requirement I made a simple JFET buffer powered by doubling (might have been tripling) the heater supply. This way you are not adding to the LT load.

Last edited by PJL; 11th Sep 2019 at 4:06 pm.
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