Lewm
Dear Actusreus, If what you say is true about the JC3 load resistor for MC, I share your chagrin, but one might always open the chassis, find said 100R load resistor, remove it, and replace it with a resistor of the desired value. I do agree that the task is tedious, if one wants to play with a variety of cartridges and/or experiment with different load values.
I'm usually reluctant to mess with a product that is designed in a specific way. I always think there was a reason why a designer made his choices the way he did. I'd think that someone like John Curl knew exactly what he was doing when he fixed the impedance at 100 ohms, even though it is rather curious given other phono preamps in this price range.
Atmasphere
This is almost as frustrating as John Curl's JC-3 phono preamp offering only one impedance setting of 100 Ohms for MC. That one I'll never understand.
The reason is if the preamp is resistant to RF at its input, the load on the LOMC is not critical. Its only there to reduce RF caused by the inductance of the cartridge interacting with the capacitance of the interconnect cable, which can form a tuned RF circuit. The resistor destroys the 'Q' of the circuit. IOW if the preamp works right, the value of the resistor is not important since it only works at RF frequencies.
Atmasphere, I have to admit I don't fully understand your explanation as I don't have a technical background and my understanding of technical intricacies involved in designing playback equipment is rather limited. This particular aspect of the JC-3's design baffled me as the great majority of phono preamps in this price range (and certainly above) offer adjustable impedance settings for MC cartridges. It was also my understanding that it is so because impedance always mattered with MC carts, just like capacitance with MM carts; a mismatch can result in a less than optimal sound that the cartridge is capable of (usually expressed as too harsh on top or too mushy at the bottom). Admittedly, I played with load impedance settings in my friend's setup once with his remotely controlled Aesthetix phono preamp so any effect should have been immediately audible, but the differences were very subtle, if any. However, we both preferred his Dyna XV-1s at about the same setting, and we reached that conclusion independently. Fluke? Perhaps.
Jmcgrogan2
Actusreus, I would think that 60 db of gain from a phono stage would be enough for any cartridge, unless possibly if you are considering running through a passive controller instead of an active preamp. Most will run the Chinook through an active line stage preamp (as the OP is here) which will add more than enough gain for any cartridge.
If you use the KAB calculator, 60 dB of gain is optimal for MC cartridges with an output of 0.4 mV or higher. If that's true, the Chinook does not have enough gain for most Dynavectors, just to mention one popular manufacturer. The KAB calculator does not seem to take the gain of the line stage into consideration. From my experience, I certainly had phono preamps that simply did not have enough gain to produce a sufficient volume level with the cartridge I used (in this particular case a MM), even though the same amplification produced more than adequate volume levels for CDs. Doing the math, the KAB calculator seemed to be pretty spot on. My current phono stage has 55 dB of gain in the MC setting and I feel anything less would not be sufficient for my Lyra Delos's 0.6 mV despite the fact that my line stage has a variable gain. It appears that having the optimal gain at the phono stage level is more crucial than having enough gain downstream. At least in my less than expert opinion...
