[Amps] Clean -vs- Unclean

[HAROLD B MANDEL]

This question concerns signal cleanliness.

A recent thread talks about unclean signals
from poor amplifier construction.

As an aside, talking with one of the commercial
manufacturers earlier, I was told that his products
are -49dB down, as opposed to others that were
-43dB down.

What specific components lead to a betterment
of this parameter?

In a simple triode, running GG, does the choice
of value of the plate blocker, padder caps and
tune/load capacitors matter?

Thanks,

Hal
W4HBM