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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: Lots of vintage components! posted by jpirroni3@comcast.net on July 18, 2012 at 18:22:35:
Get rid of that WW pot in the cathode circuit and just use the 10 ohm resistor. That pot is a liability. Better yet, use a separate 10 ohm resistor per tube so you can match each one independently.
The reason for the 11.1 ohm resistor is a bit interesting. In the early 1960s a precision volt meter was expensive. $10 digital meters were science fiction. The cheap hobbyist analog meters were rather inaccurate at such low voltage readings. So Mr. Hafler made the proper bias current work out to be 1.56 volts. That just happens to be the terminal voltage of a D flashlight battery so you could calibrate your meter to a fresh battery and the Dynaco bias should be the same!
Today we have precision volt meters that can be bought at an auto parts store for less than $10. So by just using the 10ohm resistor, you can easily calibrate your bias.
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Follow Ups
- Some Advice... - gusser 18:45:19 07/18/12 (2)
- RE: Some Advice... - jpirroni3@comcast.net 19:50:24 07/18/12 (1)
- Just keep in mind... - gusser 10:19:39 07/19/12 (0)
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