Are most tube preamps ‘ultra linear’?

Not all preamps are one tube, single ended. Some use two tube and are push/pull but all are still class A. The low power of a preamp is imple to make class A.

Single ended amps are not so obviously the purest thing around. They are low power with lots of second order harmonic distortion. They react with reactive speaker loads so their output is not flat. And they are non-linear. They compress the negative half of a wave form relative to the positive half.

Every format has trade offs.

HS, lots of stuff to learn.  God must be amazed at the size of this rabbit hole relating to his creation of hearing, a truly remarkable gift to our existance.

Single ended amps are not so obviously the purest thing around. They are low power with lots of second order harmonic distortion. They react with reactive speaker loads so their output is not flat. And they are non-linear. They compress the negative half of a wave form relative to the positive half.

@dynamiclinearity  the first sentence explains the why of the last sentence- the two are one and the same.

So what does last sentence mean?