09-28-11: Banquo363
Am I right in believing that non-ideal impedance match between phono stage and LSA results in a attenuation of the high end? Perhaps it hasn't bothered me because of my old ears?
Not necessarily. It depends on how the two impedances vary as a function of frequency. If neither varies significantly over the frequency range, there would be no adverse effects, just a slight gain reduction.
I couldn't find any indications of the output impedance vs. frequency characteristics of your Allnic H-1200, but more often than not the most significant output impedance variation of a tube-type line-level component will be an impedance rise at deep bass frequencies, due to the output coupling capacitor that is commonly used. That would cause deep bass frequencies to be attenuated, assuming the input impedance of the destination component is reasonably flat as a function of frequency.
What will attenuate high frequencies is a combination of high output impedance (at high frequencies) plus high cable capacitance (or, in theory, high input capacitance of the destination component, but that generally doesn't occur in practice, and I assume does not occur with the LSA).
Regards,
-- Al