Paperw8, regarding my detailed investigations into load impedance values, the starting point was my basic knowledge of electrical design (that when inductive generators are involved, any capacitance present will influence the results), the second stage was SPICE analysis, and the third stage involved using signal generators and verifying how different load networks affected the electrical response curves, including above 100kHz.
I generated one set of data for the Delos, and another for the Kleos, and the instruction manual for each cartridge includes this information. The two sets of numbers are similar, but not the same. Although the topology of the electrical model is the same for both cartridges, the electrical values of the signal coils are different, and therefore the two should be treated as individual cases.
The overall take-home message is that the optimal loading changes, depending on how much capacitance there is between cartridge and phono stage. The less capacitance there is, and/or the better your phono stage is at handling ultrasonic energy (above 100kHz), the lighter the electrical load can be. I believe that this is true not only for all of the Lyra cartridges, but most other low-impedance low-output MC cartridges as well.
Cartridges with comparatively higher output levels likely have more inductance, and this means that the frequency range of all electrical effects will come down. The nature of the interaction and reactance between coil inductance and cable/phono stage capacitance is the same as with low-output low-impedance MCs, but where the frequencies involved are in the high-ultrasonic range with low-impedance MCs, the frequencies involved will get closer and closer to the audible range as the coil inductance increases. In either case, the phase response will start shifting at a much lower frequency than the frequency response (1-to-10 ratio as a general rule of thumb), so if you feel that phase response is worth worrying about, any reactive anomalies in the frequency response should be kept above at least 200kHz. This is a strong argument for the basic superiority of low-inductance low-output cartridges - assuming that the phono stage is up to the job.
BTW, I'd like to mention that the Delos has been receiving favorable reviews in the audiophile press. Micheal Fremer gave the Delos a positive review in the 2010 August issue of Stereophile, and there is supposedly a positive writeup of the Delos in The Abso!ute Sound (although I've not read the article).
The 2010-08 (August) issue of the German audio magazine Stereoplay has a 5-way cartridge shootout between Ortofon's Cadenza Red, Ortofon Cadenza Blue, Benz-Micro Wood SL, Kuzma KC2 (a ZYX OEM), and Lyra Delos. The Delos was picked as the best-sounding cartridge in this particular comparison, and was the only cartridge to earn the "Stereoplay Highlight" plaudit. The Stereoplay review is particularly interesting in that it offers a much more comprehensive set of measurements and tests (of all cartridges involved) than any article that I have seen in the English-speaking audio press. Well worth reading if you have an interest in any of the cartridges mentioned.
cheers, jonathan
