Where to insert the step up transformer

Without the specs of yr SUT, cable, phono, & cartridge, there cannot be a "best" place. I recommend you try your 1ST solution first, then the second, in the order you present them.
You should check for clarity of sound midrange upward, and dynamic impact. Choose a record accordingly. Don't worry about "liking" the sound for now. Regards

Hi,
let me put it this way, since I do not know if your step-up has a cable coming out from the secondary side (the one to go to the phono-pre).
The tonearm cable will go into the primary of the set-up, it would say Input and a range of Impedance numbers, such as 4 - 18ohm or so.
This cable is now less critical than with having no trannie, due to it working more on current than voltage i.e. less capacitance critical.
The secondary or Out-put (often already having an RCA cable attached) will go into your phono/phone-preamp input RCA.

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!
Good luck,
Axel

Hi Cucurello,
you say:
>>> An unused Ortofon MC10 with step up transformer <<<
So, here is one more point, going with what Gregm has noted.
As he is correct in saying, that making definitive recommendations without knowing the type of SUT is not possible as such.
I have assumed it is a 'matched' SUT maybe also from Ortofon?
If not, you maybe in for some fun...
Firstly because of the step-up ratio having to meet the phono-pre's overload spec. i.e. no more than 7.5mV to be on the save side. (Most would quote 10mV, but it's better to keep it at arround 5mV)

Your MC-10 according to my info has 0.1mV output, that mates with a Ortofon T3000 with 30dB step-up = 1:31.6 ratio ---- 0.1mV x 31.6= 3.16mV which looks jolly fine.

In fact a T10 (my best guess what you may have) 32dB step-up = 1:39.9 ratio would work even better i.e. 0.1mV x 39.9 = ~ 4mv a very good phono-pre input-match.

The next issue after phono-pre input-voltage, is the impedance matching. In the case of a Ortofon T10 I guess you aught to be just fine without further ado.

If your trannie is some other item, this may, or may not be the case. In this case you'd have to look into trannie loading of either the secondary (going to the phono-pre), or more 'tricky' (a solder iron and some soldering skill is needed) primary loading (going to the tone arm/cart).
I hope that's not your case, as then it could get more 'information intensive' then you care for... :-)
Axel

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