Using a Denon DL110 HOMC, I found I liked it best running into a 1k ohm load (1.5k ohms also worked fine). I didn't like it as much into 47k ohms. The sound got thinner, highs more 'scratchy'.
Denon DL110 coil inductance is supposed to be 380uH (microhenries, not millihenries). "Output impedance" = 160 ohms.
The Lcoil of a typical MM is more like 500mH (millihenries), which is 1000X the DL110's Lcoil.
Is 380mH a low enough Lcoil to make use of an input transformer possible? I'm asking this more out of curiosity than from any real desire to pursue the idea, but it could be interesting.
My understanding is that the higher output of an HOMC cart (as compared to an LOMC) comes from more windings on the coil (= a heavier coil) for more inductance. That is likely to make the mechanical response of the stylus slower.
OK, so plugging the DL110 numbers into the equation 6A3sUMMER posted, I get the following:
1/(2 x pi x (Root of (L x C)))
2pi = 6.2832
L = 0.00038
C = 0.000000001275
L x C = 0.0000000000004845
Square root of 0.0000000000004845 = 6.9606034221179416364101895080211e-7
6.2832 x 6.9606034221179416364101895080211e-7 = 4.3734863421851450889892502716798e-6
1/4.3734863421851450889892502716798e-6 = 228,649.8
228,650 Hz ???
(maybe I did that wrong...)
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228kHz. Right, as long as we have accounted for everything that is significant.
More to measure, so we can calcutate:
There will be some distributed capacitance across the transformer's secondary.
There will be some shielded cable capacitance that connects from the transformer secondary to the amplifier preamp input.
Those two capacitances will add up, and be multiplied by the square of the transformer's turns ratio (5 x 5 = 25 times those capacitances, for example).
More to measure, so we can calcutate:
There will be some distributed capacitance across the transformer's secondary.
There will be some shielded cable capacitance that connects from the transformer secondary to the amplifier preamp input.
Those two capacitances will add up, and be multiplied by the square of the transformer's turns ratio (5 x 5 = 25 times those capacitances, for example).
The Denon DL-110 and (sadly lamented, now gone) DL-160 are a special case for phono cartridges' impedances, having the best of both worlds, low-enough-to-not-matter inductance and a small (almost, maybe? ideal) source resistance. "Noise matching" of their impedances is trivially easy for any amplifier that's not dominated by 1/f noise. High frequency response is essentially limited only by the mechanical and geometrical constraints of the microgroove format - PVC compresses, especially at the tons per square inch pressures of peak cutting velocity and this compliance resonates with the effective (referred to stylus tip) mass of the moving system: stylus plus some of the cantilever plus some of the generating coils and whatnot, all 1/2 order proportional to their distance from the pivot. No news there.
But, at all cutting velocities, some vinyl deformation occurs. Hopefully, given a rest, the PVC will (mostly!) spring back into its original stamped (*) location. At the time of playing though, the deformation resonates with the effective moving mass of the rock at the end of a tube being dragged down the groove. This resonance obviously varies with both contact surface area and magical unknowable properties of the PVC used. Effective moving mass is calculable; contact area varies with stylus shape design and wear, but nobody ever talks about vinyl compliance at tons-per-square-inch pressure. Even Shure, who did all the heavy lifting (also credit to Stanton for excellent work in stylus - groove surface interface) never published PVC compliance figures. But otherwise the math is simple, mass times compliance is exactly like L times C as a resonance. Reciprocal of the square root of the product - exactly the same.
Why does all this matter? Because phono playback at high frequencies is (at best!) a balance between this stylus effective mass x vinyl compliance resonance and the following electronics' (including the cartridge's generator inductance and stray capacitance) own frequency (magnitude, for the hardcore) response. If the electronics is immune to the raw, unadulterated magnitude (meaning: voltage amplitude) response of a phono cartridge, like a Denon DL-110, with low source impedance, and therefor has little frequency response interactions with loading impedances, then the total system will see a high frequency response very much dominated by the raw mechanical down-n-dirty frequency response of the resonant stylus effective mass x vinyl compliance.
If the playback electronics isn't tuned for this particular case, of a low (read: negligible) impedance, then it is tuned for some other likely general case, maybe assuming a usual inductance and some possible parallel capacitance, historically the norm - the plan was to low-Q resonate the cartridges' loading somewhat below the vinyl interface resonance and let it all balance out. Seems to have worked - everybody still plays their old PVC, and some claim it's better than butter.
All good fortune,
Chris
But, at all cutting velocities, some vinyl deformation occurs. Hopefully, given a rest, the PVC will (mostly!) spring back into its original stamped (*) location. At the time of playing though, the deformation resonates with the effective moving mass of the rock at the end of a tube being dragged down the groove. This resonance obviously varies with both contact surface area and magical unknowable properties of the PVC used. Effective moving mass is calculable; contact area varies with stylus shape design and wear, but nobody ever talks about vinyl compliance at tons-per-square-inch pressure. Even Shure, who did all the heavy lifting (also credit to Stanton for excellent work in stylus - groove surface interface) never published PVC compliance figures. But otherwise the math is simple, mass times compliance is exactly like L times C as a resonance. Reciprocal of the square root of the product - exactly the same.
Why does all this matter? Because phono playback at high frequencies is (at best!) a balance between this stylus effective mass x vinyl compliance resonance and the following electronics' (including the cartridge's generator inductance and stray capacitance) own frequency (magnitude, for the hardcore) response. If the electronics is immune to the raw, unadulterated magnitude (meaning: voltage amplitude) response of a phono cartridge, like a Denon DL-110, with low source impedance, and therefor has little frequency response interactions with loading impedances, then the total system will see a high frequency response very much dominated by the raw mechanical down-n-dirty frequency response of the resonant stylus effective mass x vinyl compliance.
If the playback electronics isn't tuned for this particular case, of a low (read: negligible) impedance, then it is tuned for some other likely general case, maybe assuming a usual inductance and some possible parallel capacitance, historically the norm - the plan was to low-Q resonate the cartridges' loading somewhat below the vinyl interface resonance and let it all balance out. Seems to have worked - everybody still plays their old PVC, and some claim it's better than butter.
All good fortune,
Chris
