Hi Rccc,
this cart has:
Output voltage: 0.7 mV (at 5 cm/sec) or some say 0.8mV ?
Coil impedance: 50 Ohm (DCR)
The first item to look at with any step-up is phono-pre overload.
0.7mV with 1:10 step-up (20dB gain) = 0.7 x 10 = 7mV or maybe 8mV as to which ever spec. is closer.
That tells me you can NOT, should not, go with a higher step-up ratio SUT.
Now, I guess you have some reason to look for a change, and I can guess you are looking for some more resolution, air, sparkle, etc. If this is so, then you have to stick with your 1:10 but try with some trannie loading.
A 1:10 SUT has a 'natural impedance' of 470 ohm as you mention correctly - with a 47k ohm phono-pre input that is, and is pretty standard.
Your cart has 50 ohms spec. DC resistance (DCR), so lets look at a more 'open' sounding impedance match.
With an SUT it gets more 'chirpy' if you are going down with impedance, contrary to the non SUT set-up. All within reason of course. I worked with 2.5 x DCR = 2.5 x 50 = 125 ohm and could be a good try.
To get there you have two options, secondary or primary loading, primary will need you to do some soldering inside the trannie, so you first want to try secondary loading by using some available load settings of your phono-pre or what ever there is to change your cart loading inside the phono-pre.
So what resistor value would that be?
a) 470 * 125 / (470-125) = 170ohm * square of winding ratio 10*10 = 17k ohm loading resistor for secondary side loading to get your cart see 125 ohm in place of 470 ohm.
This you can use as an example for other maybe higher values e.g. using 5 * 50 ohm = 250 ohm could be the next one to try if the above is not working for you.
Then:
b) 470 * 250 / (470-250) = 534ohm * 100 = 53k ohm ---- BUT
already this looks like a VERY high loading resistor and will mess-up your sound more than it may actually improve it.
In fact anything much higher than 25k ohm sounds not too good to me (just gut feeling, you can try).
So next, the reverse calculation for a 25k ohm secondary load resistor:
47k * 25k / (47k >>+ >+<< in this calculation) i.e. using a 25k resistor on secondary will make your cart see 160 ohm in place of your current 470 ohm.
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If secondary loading is not to your liking/expectation, primary loading can be your next thing to try.
Again I'd try for the same ball-park start value of 125 ohm for the cart to see.
c) 470 * 125 / (470 - 125) = 170 ohm loading resistor on primary, and from there on you could go up in steps like 250 ohm and say 500 ohm max. I think that should cover the range, methinks.
Let's hear what you will find out.
Greetings,
Axel
PS: Infact one more thing! Have you tried the lowest capacitance inter-connect for your secondary to phono-pre connection? If not, it's the VERY first thing to try before anything else!!
