What does the "high gain" option refer to when buying preamp tubes

All 6SN7s tubes are the same gain!

6SN7 is a dual triode vacuum tube with an eight-pin octal base. It provides a medium gain (20 dB).

@yogiboy  , thank you.

But in that case do you know what Tube Depot is referring to with that option that they want $2 extra a tube for?

The text below was found on Harmony Central from a post were someone asked the same question 15 years ago. I don’t know if it’s the correct explanation or not but at least it’s an answer to your question-

Tube Store options

Standard Test = normal test to make sure tube is operational

High Gain = actually opposite of what it sounds, handles more high gain therefore making it actually have LESS gain

Matching = should be self explanatory, matches tubes to be same

Balanced Triodes = what you normally use for phase inverter slot

Matched + Balanced Triodes = same only matched, probably won't use for guitar head

Low Noise and Microphonics = mainly for playback equipment

@designsfx  , thank you!  Since I feel I have too much gain, the "high gain" option would probably be what I would be looking for.  Thanks again.

Tube depot charges $2.00 to test the tube. Like I said the gain is the same on all 6SN7s tubes. No test is going to change that! You should give them a call to explain what they mean!