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Too low plate R value for a triode ? and CCS substitution?

I have just bought a BAT VK5se preamp for good deal.
What I have found is the plate resistor being abnormally low value for the parallel 2 section of 6h30. The plate R of 6h30 per section shown in EH datasheet is 840 ohm per section then parallel 2 section is 420 ohm.

However the plate resistor is only 1250 ohm which is less than 3 times of 420 parallel section of 6h30. Is it normal for high priced preamp design?

Apart from smaller gain, does the small R value of plate load resistor affect the dynamic of preamp which is my major concern.

The B+ is 138V and the plate volt is measured as 80V idle running 22mA per section. It means I can have 58V to play with CCS if I remove plate resistor and put in place the CCS.

What sonic improvement I will get if I use CCS, and what type CCS do you recommend?

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Topic - Too low plate R value for a triode ? and CCS substitution? - Eric Chan 07:09:42 03/22/17 (12)


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