That is nomenclature.
The SUT has writen on the body that it is good to use with 40r carts, but it does not signify the cart "sees" 40r for load.
About add a resistor in the secondary transformer can narrow frequency response and cause ringing, not a good idea to change the load on the secondary of the transformer to modifie the load seen by the cartridge.
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The turns ratio is the turns ratio. It depends solely on the ratio of turns on the primary to the turns on the secondary.
Load impedance has nothing that can change the turns ratio.
If you are working with emf (in effect output voltage when the load impedance is infinitely large) then the turns ratio also defines the emf ratio.
post6876 shows what to correct to see the actual/real output voltage taking account of winding resistances.
If we temporarily ignore winding resistances then the 35.4 turns ratio allows us to predict the output emf.
The gain will be ~ 20 * log(turns ratio) =+31dB.
measure the windings and apply the correction for output voltage. The effective gain is likely to be 1dB to 6dB lower than that emf gain prediction, i.e. +25dB to +30dB.
Neither of these are close to +20dB.
Load impedance has nothing that can change the turns ratio.
If you are working with emf (in effect output voltage when the load impedance is infinitely large) then the turns ratio also defines the emf ratio.
post6876 shows what to correct to see the actual/real output voltage taking account of winding resistances.
where does this come from?
If we temporarily ignore winding resistances then the 35.4 turns ratio allows us to predict the output emf.
The gain will be ~ 20 * log(turns ratio) =+31dB.
measure the windings and apply the correction for output voltage. The effective gain is likely to be 1dB to 6dB lower than that emf gain prediction, i.e. +25dB to +30dB.
Neither of these are close to +20dB.
HI Andrew
you are welcome to help us on load difference active vs passive
That's confusing, doesn't exist active or passive load because step-up are also passive like resistors.
Please read the info about the Denon AU340 SUT.
The 1:10 winding works best with the DL103 and has a primary winding inductance of 40ohm. That does not mean that the cart is loaded at 40ohm because you now know it depends on the input impedance of the Riaa amp.
1:10 means 470ohm load for 47k riaa input impedance.
This Denon SUT also has another setting, in this case with a 1:33 ratio and presenting a 3ohm primary impedance. (I did not like this setting with the Denon DL103)
For a perfect explanation look for "Step-Ups and MC Cartridges | The Secrets of a Successful Marriage | Vinyl Engine." where it is stated:
<<Now, on a step-up you’ll find internal impedances indicated: for instance, take a look at a DENON AU320, two positions are possible: 3 ohms and 40 ohms. So this step-up should be good with cartridges of internal impedance of 3 ohms and 40 ohms. Now the problem is, that for the moment, the load impedance used in that step-up is not known (but we’ll soon know this very important information!). We’re only sure that this load impedance is superior to the internal impedance. And secondly, the load impedance given by a manufacturer for its cartridge is the one you should use on active devices; the one you should use on passive devices is not generally the same and is superior to the load impedance given by the manufacturer.
But, why are only internal impedances indicated on a step-up?
The main reason is certainly the fact that, as I already indicate, natural impedances are not constant: they are a function of the impedance of your MM input. For instance, if your MM input has a 10 Kohms impedance, with a 1:10 amplification>>
Enjoy
"primary winding inductance of 40 ohm" is a typo I guess; inductance is expressed in henries.
Looking at that specification card of the Denon AU340 SUT all I can say that they should have specified 3 resp. 40 ohms as source impedance of the particular cartridge (better still source resistance) instead of "primary impedance".
In general 3 ohm MC carts have low output, therefore need much gain (by using the higher step up ratio which should be the 1:33 option of the AU340).
At the same time the 3 ohm source impedance will need less inductance of the transformer primary; a higher impedance cartridge like the DL103 connected to the 1:33 will be very bass shy because there is not enough induction, and should therefore use the 1:10 connection. I guess that the 1:33 connection was for the low impedance DL301 series of cartridges.
Finally, the winding ratio of the step-up transformer reflects the secondary load back to the cartridge: 47k resistor as secondary load will be seen as a 470 ohms load by the cartridge in case of 1:10. This is said already, and so it is.
