Calculating cathode follower using 12AU7 for 90V supply - diyAudio
 Calculating cathode follower using 12AU7 for 90V supply
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 11th October 2014, 05:40 AM #1 diyAudio Member   Join Date: May 2011 Calculating cathode follower using 12AU7 for 90V supply Hi everyone, Need help calculating resistors for cathode follower. Here is schematics: Power supply will be 90V. My estimate values: RL = 3 kOhm RB = 200 Ohm RG = 100 kOhm Cin = 2uF Cout = 2uF
 11th October 2014, 06:24 AM #2 diyAudio Member     Join Date: Mar 2009 Location: Buenos Aires - Argentina For close to 45V on cathode, Rb=390r and Rl=18k From: Ignore the red line, I just "borrowed" this graph from another page.
 11th October 2014, 06:40 AM #3 diyAudio Member   Join Date: May 2011 Why 45V?
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Quote:
 Originally Posted by gooduser Need help calculating resistors for cathode follower...

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Location: Ashland,Ky U.S
45V is half of your 90V B+. Generally the best place to start. Blue line.
Attached Images
 12AU7 plate curves.jpg (340.0 KB, 189 views)

Last edited by jerluwoo; 11th October 2014 at 07:28 AM.

 11th October 2014, 07:21 AM #6 diyAudio Member   Join Date: May 2011 Load impedance 980 Ohm, max input level - CD or iPod
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Join Date: Feb 2006
Location: Ashland,Ky U.S
Quote:
 Originally Posted by gooduser Load impedance 980 Ohm, max input level - CD or iPod
Hope you like distortion.

 11th October 2014, 07:35 AM #8 diyAudio Member     Join Date: Aug 2005 ideally Rk like a plate load resistor, should equal 2Xrp at the operating point - that's an awfully low Z but not a lot of voltage to swing
 11th October 2014, 08:02 AM #9 diyAudio Member   Join Date: May 2011 I'm assuming I should either increase voltage or load resistance? What would those be for operating without "distortion"? Thank you.
 11th October 2014, 08:10 AM #10 diyAudio Member   Join Date: May 2011 Would increasing load resistance to 1.8k help?

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