richardbrand OP
excerpt from Sumiko
"(2.5mV is typical for a high output moving coil cartridge, 4-5mV is typical for a moving magnet cartridge)."
https://sumikophonocartridges.com/high-output-mc-cartridge/
What innovative, unconventional cartridge designs can you recommend?
Most cartridges have a stylus and cantilever where the transducer (magnet, iron or coil) sits on the far end of the cantilever. What other designs are there?
I am mindful of two designs which put the business end right on top of the stylus. The first is the moving coil (MC) Audio Technica AT-ART1000 which places two tiny coils, each 0.9-mm diameter, with eight turns of wire directly above the stylus. Australian price is about AUD-7000 and there apparently is a newer model, slightly less exxe. the ART1000X. This has square coils for a bit more output, and threaded mounting holes.
A downside is that stylus replacement involves a factory maintenance program and the Australian website page describing this service does not exist.
Another design is optical, exemplified by DS Audio's range. While these still need a stylus to trace the groove, the signal is produced by reading the intensity of light produced by a Light Emitting Diode (LED) hitting two sensors. Between the LED and the sensors are two 'shades' mounted above the stylus which change the amount of light as the stylus vibrates. These cartridges need a special "photo-stage" to replace the conventional phono-stage which is an additional expense.
Australian prices including photo-stages range from AUD-2,150 for the DS-E1 to the DS Master 3 at approximately AUD-40,800, which is a bit outside my price range! Where is the sweet spot?
What other way-out designs are there?
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The G’s is totally a function of the frequency being produced and the modulation and there is a calculation for it - read this article - Dr. A. M. Max, Disc Phonograph Records, Max, RCA Engineer Magazine 1966-08-09 1966-08-09.pdf which also calculates the force from a spherical stylus of different dimensions and different VTF, and the "calculated" forces at 2.5-gm VTF can range from 65,800-psi to 121,300-psi. However, the G-forces developed have only a minor impact and it’s because of the very low effective tip mass with modern cartridges being very low Effective Tip Mass | myhi.fi. Note that the record does deform under the forces of the stylus, but provided the forces remain in the ’elastic’ region, no permanent deformation occurs. However, if the stylus mass is too high (generally considered >5-gm), then the forces exceed the elastic region and ’plastic’ deformation can occur. The Dr. Max article addresses the elasticity of the record with greater detail in this article - Groove Deformation in Gramophone Records. FWIW, on a different but related to records, this very recent article 2023, is excellent on the subject of tracing distortion Tracing Distortion on Vinyl LPs Take care, Neil |
Agree that the highest G-forces are only generated where the acceleration of the stylus is at its maximum. Since a long ton is 2240-lbs (and is close to a metric tonne but about 10% more than a short ton of 2000-lbs) we can divide 65,800 and 121,300 by 2240 to get about 29 and 54 ton per sq inch. This is beyond the breaking strength of mild steel and way higher than my calculations for a line contact stylus. Something has to give, and what gives is the vinyl! It deforms elastically around a conical stylus, increasing the contact area and reducing the pressure. I recall advice that the same side should not be played immediately in order to give the vinyl time to recover its original shape. |
@richardbrand @elliottbnewcombjr,
It's probably best not to play the same track repeatedly, but for the album, there is a 15-20 min delay before the same spot is replayed, and the how much is the record actually heating - very little. The thermal conductivity of the diamond is the highest of all materials - ~1000 Watts/(meter-deg-Kelvin) - List of thermal conductivities - Wikipedia. Compare that to PVC or most other plastics - Plastics - Thermal Conductivity Coefficients (engineeringtoolbox.com) at <1-W/m-K). Additionally, the cantilever even if boron (~27 W/mK) which has the least of the various cantilevers (other than cactus) has a thermal conductivity much higher than the record. The diamond and cantilever are going to transfer the heat much faster and therefore heat much faster than the record. Additionally, consider the record is moving between 51-cm/sec (510,000-microns/sec)-at the outer cut to 25-cm/sec (250,000-microns/sec) at the inner cut. If the stylus contact width is 2.5-micron, the stylus is in contact with the record at a spot 2.5-microns wide at most (2.5-microns)/(250,000-microns/sec) = 0.00001-sec (10 microseconds). The amount of energy (watts) to produce heat can be no more than what is being used to spin the record - it's the conservation of energy, and as the record rotates, air is being moved which provides some cooling. |
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