|
Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
Register / Login
|
In Reply to: Why do I have DC on my cathode-biased input tube's grid? posted by Alexo on April 27, 2007 at 08:39:54:
Years ago Audio Amateur published an article called the 'Last PAS'. The update article was about doing an over-the-top update to the PAS 3, which uses 12AX7s in the line stage.The article had a 680 ohm resistor in the cathode- a mile off from the correct value. Given a 120K plate resistor, I would suspect a 2.21K to 2.74K cathode resistor will work much better!
If you want the exact value, obtain a 5K pot and install it in the cathode circuit. Then run a sinewave into the circuit and observe the output with an oscilloscope. Vary the resistance until the sine wave peaks. Then increase the value slightly to deal with tube variance. remove the pot carefully and measure it. Obtain a fixed value and install it- Bob's your uncle.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: 680 ohm resistor is wrong! - Ralph 09:34:23 04/27/07 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
