help with s/n ratios of preamps and Moving Coil


Guys - i hope someone can clarify this for me. Why is it that most preamps/phono stages are rated at a lower S/N ratio for Moving Coil carts vs their Moving Magnet counterparts. I just ordered a clearaudio pre-amp for a Benz low output cartridge, however i realised that s/n ratio says > 68 db.. Is that enough, dont i want something >80 for MC carts.. i cant find any advice on this on the www

thanks!
aquaanox
Slightly lower channel separation and slightly higher THD figures will not be as overtly apparent as a higher inherent noise level, in my view.

How much the low signal to noise ratio will bother you is somewhat dependent on your speaker's treble character and how close you sit to the speakers. Personally, I'd go for a phono preamp with as high a signal to noise ratio as I could afford, especially with a low output moving coil cartridge.

Ultimately, you have to set it up and try it to see if the highish background noise level will bother you in your particular system. Plugging it into an effective AC line filter may help it a bit as well.
Yes, everything will be plugged in via a AC line filter. I am used to a much cheaper NAD pp2 pre-amp with this cartridge and have no idea what the s/n ratio is but it sounded good to me.

I can only hope the that clearaudio smart phono will be a noticeable improvement. Audio guys at the store said to completely ignore the numbers and concentrate on the overall quality of the preamp and that clearaudio makes really good stuff. I guess, if it doesnt work ill just have to switch to a MM cart, the S/N spec for which is higher on this preamp. Sorry im very new to vinyl, and not having the new preamp for another week or so is making me ponder all this stuff.
oh and btw.. does the S/n ratio include the noise level of the pre-amp itself. for example, some cheaper preamps may create their own noise levels and their s/n ratio's maybe higher taking that into account; while a more expensive preamp may be dead quiet itself and has a slightly lower S/N ratio. Does this make sense ?
The published s/n ratio for the phono stage does not include the s/n ratio of the line stage itself.
I guess the other thing to consider is @ what frequency manufacturers rate the S/N ratio for MC carts. Ive seen some examples rated at 20kHz and some at 1kHz.