Regarding the issue of cartridge loading, in a past thread here Jonathan Carr (Lyra cartridge designer, who I believe has also designed some phono stages) stated as follows:
The relevance of the Hagerman link Ralph provided in his previous post is that it illustrates the high frequency resonant peak (i.e., the "spike") formed by the interaction of the inductance of the cartridge and the load capacitance that it sees.
I am not in a position to say whether or not the **only** relevance of resistive loading of a low output moving coil cartridge is to control that peak, and its potential effects on the particular phono stage. However I certainly wouldn’t consider the possibility that it could often at the very least be an important factor in the performance of a system to be "out of the world," as Roger stated.
Also, while I don’t recall the exact numbers, Ralph has stated in some past threads that he has observed remarkably high levels of energy emanating from LOMC cartridges at ultrasonic or RF frequencies.
Also, FWIW, I’ll mention that Keith Herron, whose company and products (especially his phono stage) are about as non-controversial and highly regarded as they come, suggests that with his particular phono stage no loading whatsoever will often be found to be preferable with LOMCs, regardless of the cartridge type. (The LOMC input of his phono stage is FET-based, and it applies a load resistance to the cartridge that is nearly infinite when load resistors are not connected externally, to RCA jacks that are provided for that purpose). And I have found that to be the case in my own system, with an AT-ART9 cartridge having a recommended load of "100 ohms minimum."
Finally, without placing blame (although I have my own thoughts about that) I’ll just say that it’s a shame that an otherwise wonderful thread is compromised by the fact that two long-time designers of highly regarded audio electronics can’t deal with each other in a more respectful and matter-of-fact manner.
Regards,
-- Al
I should now debunk another myth regarding loading, which is that low-impedance MC cartridges are insensitive to capacitive loading. OK, the MC cartridges themselves aren’t particularly sensitive to capacitance, but the inductance of the cartridge coils will resonate with the distributed capacitance of the coils and the capacitance of the tonearm cable to create a high-frequency spike, and this spike certainly is sensitive to capacitance. In general, the less the capacitance the better. Having more capacitance (across the plus and minus cartridge outputs) will increase the magnitude of the high-frequency spike and lower its frequency, neither of which is good news for phono stage stability or phase response.
Generally speaking, the greater the capacitance across the plus and minus cartridge outputs, the heavier the resistive loading needs to be to control the resulting high-frequency spike. Conversely, less capacitance allows the resistive load on the cartridge to be reduced, which will benefit dynamic range, resolution and transient impact.
The relevance of the Hagerman link Ralph provided in his previous post is that it illustrates the high frequency resonant peak (i.e., the "spike") formed by the interaction of the inductance of the cartridge and the load capacitance that it sees.
I am not in a position to say whether or not the **only** relevance of resistive loading of a low output moving coil cartridge is to control that peak, and its potential effects on the particular phono stage. However I certainly wouldn’t consider the possibility that it could often at the very least be an important factor in the performance of a system to be "out of the world," as Roger stated.
Also, while I don’t recall the exact numbers, Ralph has stated in some past threads that he has observed remarkably high levels of energy emanating from LOMC cartridges at ultrasonic or RF frequencies.
Also, FWIW, I’ll mention that Keith Herron, whose company and products (especially his phono stage) are about as non-controversial and highly regarded as they come, suggests that with his particular phono stage no loading whatsoever will often be found to be preferable with LOMCs, regardless of the cartridge type. (The LOMC input of his phono stage is FET-based, and it applies a load resistance to the cartridge that is nearly infinite when load resistors are not connected externally, to RCA jacks that are provided for that purpose). And I have found that to be the case in my own system, with an AT-ART9 cartridge having a recommended load of "100 ohms minimum."
Finally, without placing blame (although I have my own thoughts about that) I’ll just say that it’s a shame that an otherwise wonderful thread is compromised by the fact that two long-time designers of highly regarded audio electronics can’t deal with each other in a more respectful and matter-of-fact manner.
Regards,
-- Al