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Hoffman Amps Forum image Author Topic: Cathode bias question.  (Read 2221 times)

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Offline Tone Junkie

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Cathode bias question.
« on: January 13, 2019, 07:38:34 pm »

When going from a single resister per pair. To a single resistor per tube do I halve or double the amount of resistance . example 1- 400 ohm resistor  and cap to 2- 200 ohm resistors and caps.
I seem to have misplaced my notes on this.
Thanks Bill

Offline sluckey

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Re: Cathode bias question.
« Reply #1 on: January 13, 2019, 07:47:21 pm »
Quote
When going from a single resister per pair. To a single resistor per tube do I halve or double the amount of resistance
double

Your example is wrong.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline Tone Junkie

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Re: Cathode bias question.
« Reply #2 on: January 13, 2019, 10:39:53 pm »
Ok Thanks

Offline jjasilli

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Re: Cathode bias question.
« Reply #3 on: January 14, 2019, 08:31:26 am »
Actually, you don't need notes.  A cathode R is not a unique situation.  There are no unique situations - instead there is a law of physics.  Ohm's law governs.  The cathode R provides bias voltage (relative to G1).  When current flows through a R, the R causes a voltage drop.  2 Tubes draw 2X the current of 1 tube.  If you halve the current draw through the R, you need to double the R value to get the same voltage drop. 

 


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