Building a phono preamp with tubes that can match a SS one for absence of
noise and hum NOT a trivial task.

This seems like a too simplistic statement.

For moving magnet cartridges
with outputs above 2.5 mV, a 12AX7 input tube and following
6SN7 gain tube can provide entirely adequate snr.

Many SS phono stages in many SS items have worse hum and noise
than some tube phono amps.

However, with a moving coil source,
where output is down to 0.1 mV,
it isn't easy to build *any* discrete component
amplifier which is free of noise and hum.
Usually a step up transformer has been used in the past
to over come such problems and allow the benefits of the MC sound quality to be
realised.

I am using a 2SK369 j-fet as an input device in cascode with a frame grid
pentode strapped as a triode, and the snr is OK for
direct connect to MC.
The j-fet has an input noise well below a 12AX7, or any other tube I know.
Keeping the noise levels low in tube amp stages after the fet input
is not difficult if the usual rules about fine power supplies,
screening, short leads, and earthing are followed.

Vinyl is a great medium for hi-fi, until
you hear the clicks, pops and naked track noise in the middle of quiet
classical recordings.
The amp noise can usually be made to be well
below the noise of an unmodulated vinyl groove.
This noise should be similar or lower to the background noise of the
recording venue, and tape and equipment noise in the recording
studio....
For rock and roll,
the vinyl and amp noise is less important.

Patrick Turner.