Where to insert the step up transformer

If you have no out-put RCA cable comming out of the step-up (going to the phono-pre), make sure it is as low in capacitance as possible!!!!!!
The capacitance of this interconnect is 'reflected back' to the primary i.e. what the cart sees. It 'stepped-up' by the square of the winding ratio of your trannie. Example a 30dB trannie has a 1:31.6 ratio, therefore the capacitance of that cable makes your cart "see" 31.6x31.6=~1000 times the capacitance of that trannie-to-phono-pre cable!

Actually, it's the opposite, Axel. Since there are (many) more turns on the secondary side, the impedance seen looking into the primary of the transformer would be REDUCED from the secondary side load impedance by the square of the turns ratio.

As far as the op's question is concerned, in the absence of further information my instinct would be to have the longer set of cables on the secondary side (between xfmr and preamp), and to keep the cabling between cartridge and xfmr as short as possible. That way most of the noise which may be picked up in the cabling will not be boosted by the step-up transformer.

Regards,
-- Al

Yes, you are right Axel, I read it too fast. I was thinking impedance, but you had written capacitance. Capacitive impedance (reactance), of course, being inversely proportional to capacitance. Mea culpa!

Concerning the high load capacitance which the cartridge would see if the lengthier cables were on the secondary side, I'm uncertain without having specific data on the cartridge resistance and inductance. As you realize, but others may not, moving coil cartridges are essentially insensitive to capacitive loading, WITHIN REASONABLE LIMITS. What is "reasonable" after the capacitance on the secondary side is multiplied by a factor of 1000 or so would be dependent on those cartridge parameters.

I did find a reference indicating that the MC10 is rated for 0.2mv (not 0.1mv) output under the usual test conditions. I believe that cartridges with comparable outputs tend to have resistances in the vicinity of 5 to 10 ohms, and inductances in the area of 15 or 20 microhenries (0.015 to 0.020 mH). If your 0.1mv figure is correct, those numbers would probably be a bit lower, which would be in the direction of further reinforcing my next paragraph.

Plugging those inductance numbers into the resonant frequency calculator shown here, in combination with say 100,000 or 200,000 pf capacitance (100 or 200 pf from cables plus preamp, factored by the square of the turns ratio), gives resonant peaks in the vicinity of 100kHz or more, well outside of the audio band. Which in turn would probably be reasonably well damped by the 10 to 50 ohm or so resistive load that the cartridge would see, based on the 47K preamp impedance divided by the square of the turns ratio. The bandwidth resulting from the combination of inductance and resistive damping would also be in the 100kHz+ area, as shown by the calculator further down the page in the linked reference, under the heading "mc cartridges."

I am not particularly experienced in this area, while you are, and so your instincts are more likely to be correct in the absence of more specific information. But fwiw those are the thoughts that occur to me in the absence of quantitative data on the cartridge and xfmr.

Regards,
-- Al