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Hi guys amp; gals.

Are both preamp and power tubes measured in hardness or just the power tubes.

Thanks.

I think it's just on power tubes.

yup

preamp tubes are measured by their actual gain, as well as a few other characteristics

usually, they aren't graded - it's assumed that a branded preamp tube falls in the range for its type; however, some vendors now sort preamp tubes for high gain, and balanced phase inverters

for an additional charge of course

Preamp tubes aren't graded, but their tonal differences can be substantial. I think people usually worry about differences between makes amp; models, rather than among individual tubes of the same model.

Preamp tube swapping is a cheap, fun way to fine-tune your tone. You can just buy some extras and experiment, or read some reviews to achieve a specific tone. Two of the best resources on the web for tube reviews are:

Tube Depot
and
Watford Valves

Great! Thanks everyone.