Where to insert the step up transformer

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

Hi Almarg
I think you read this too fast...
*** The +++capacitance+++ of this interconnect is 'reflected back' to the primary

You talk now of IMPEDANCE --- I spoke of CAPACITANCE!

And as it so happens THAT works the other way round, I hope we can agree on that, and I totally agree on the IMPEDANCE point you made.
>>> ... the ***impedance*** seen looking into the primary of the transformer would be REDUCED <<< Oh yes!

I hope this is not too confusing to our audience :-)

Next, and there I TOTALLY DISAGREE!
>>> my instinct would be to have the longer set of cables on the secondary side <<<
NO WAY, since every bit of cable length on the secondary adds to unwanted CAPACITANCE, therefore, the shorter the better.
The cable between the primary and the tone-arm must be considered *differently* when using an SUT, since CURRENT has no issue with CAPACITANCE and RF as voltage with a minute current would have.
The SUT is like a short circuit (almost) to the cart, and increases current by more than 20 - 25 times in lieu of cart output voltage (some say it's a generator maintaining voltage, but let's not confuse that issue any more than needed)
It may sound counter intuitive, but capacitance = roll-off you hear, is because the C is REFLECTED back from secondary to the primary by the ratio squared.
RF noise is no issue on primary in my experience and due to the higher current as would be the case without SUT. ALL (most) current is converted to Voltage on the secondary i.e. and not to be confused with 'shunted loading' as in normal MC loading across the phono-pre's input.

Normally you'd go into a 47 000 ohm input impedance and added parallel/shunted loading of the phono-pre, with an SUT the cart going into a e.g. 32dB trannie sees a MAXIMUM of 30 ohm (the "natural impedance" based on a 47k phono-pre input impedance)! That, if now further trannie loading is added and quite easily 10 ohms, when applying secondary or primary SUT loading.

Therefore, put the lesser IC in front and the best and shortest on secondary.
Greetings,
Axel
PS: I did have had plenty time to get my XF-1 going with my PW MC cart...

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