Axel,
My #1 most challenging/torturous LP for reproducing clean high frequencies:
Les Plaisirs de la Renaissance, Deller Consort, Harmonia Mundi, HMU 963
That Allison Kraus record is difficult because her closely miked voice and its echoes present waveforms at high frequencies that are very close together (in time). Many systems can't avoid mushing them together, which usually sounds horrible. The Deller LP is more difficult for several reasons:
1. Deller's voice is much stronger. Bigger amplitudes challenge the tracking ability of the cartridge, the ability of the phono and other amplification stages to avoid slewing distortion or overload, the ability of the power supplies to resist being modulated by the signal and the speed and non-distorting cababilities of the midrange and tweeter drivers.
2. Deller is doubled and/or harmonized by an alto recorder, an instrument whose rich and tight harmonic structure is also difficult to reproduce. When he and the recorder hit/hold the same note or harmonically related notes, keeping the two voices separate is a severe challenge.
3. Unlike Krauss, both Deller and the recorder actually know where the notes are. ;-) Pitch stability from the TT is super-critical.
4. The recording was made in a stone hall - nicely authentic but intensely echo-ey, with multiple and extended reverberant decays.
5. One of the most challenging tracks was placed on the inner grooves (on side 2), adding smaller modulations to the challenges.
Other Deller Consort recordings would probably present similar difficulties. Keeping all these strong, closely related high frequency waveforms clean and separate is a terrific challenge. I've have other Deller recordings on CD so I know it can can be done. The trick is to do it from an LP, with its richer and more complete harmonic structures.
As Jaytea described for himself, it also took me four years of work (and a lot of money) to be able to play this LP cleanly. It's one of the first I play to test any new component or tweak because it is so unforgiving, and so satisfying when all is right. :-)
Another tough challenge in a similar way is the 'La Boheme' on Decca/London with Renata Tebaldi. On any 'La Boheme' Mimi's first big solo comes near the end of side 1, where tight inner groove modulations make the problem we're discussing more challenging. The Decca recording was also made in a sonically rich acoustic (though not stone, thank goodness!), which brings echoes into play again. Tebaldi's voice is of course more powerful and pure of tone than any pop/jazz singer, which adds amplitude and the need for tonal accuracy to the challenge.
If you can get through side 1 cleanly (which took me 2-3 years) don't congratulate yourself yet. The big crowd scenes and multiple voices on side 2 are more difficult for some components. It's a never ending battle. :-)
