How much do voltage regulator tubes affect performance?

I would not expect much of anything.

I suppose one could, measure the the voltage at the capacitors with the same context playing use the two different tubes. If that was different then that would be insightful.
It could be dangerous to do.

If it was different then I would think that it may still not be audible. But I would think that it would be hard to be audible if the voltage at the caps is steady.

Thanks holmz. Appreciate it.

1. I wouldn’t get it for sonics
2. But it is always good to have a spare ready
   1. Retire the current one as a spare if the new one sounds better.

You pick, there’s no wrong answer 😎