What trans (SUT) for a Victor mc-5E cartridge?

Raul, I can only hope that you get some help for your hostility. Did you notice that I agree with you on a choice of SUT? Perhaps you are the one who either does not read or does not fully understand. You need a certain amount of signal voltage to drive an amplifier. Typically at least 0.5V, or more is better to achieve full output. If you use the 40 ohm inputs on the AU340, you will increase the output of his cartridge from 0.2mV to 2mV. If you connect that to a typical MM stage with 40db of gain, you will derive an output from the phono stage of 200mV or 0.2V. You would want some additional gain from the linestage in order to drive an amplifier to satisfying levels. The OP himself has not posted since he introduced this thread. I am trying to be helpful to serge8, whether that upsets you or not. The 3-ohm inputs on an AU340 are of no real use to the OP, given his predetermined choice of cartridge, but the Denon is a good unit, and it wouldn’t hurt to have the capacity to accommodate a future LOMC cartridge that might have a more typical low internal resistance. I see that the OP also posted his question on Vinyl Engine, where he got a similar response from one of the guys there, without the craziness.

I just checked the specifications of the Denon AU 340 transformer. I agree it would be a good choice for the OP, if he will have enough total gain with just a 1 to 10 step up ratio. Using the 40 ohm inputs of the transformer, a gain ratio of 1 to 10 is provided. The designer of the transformer was accounting for the fact that most phono stages present a 47K ohm load, and the resulting 470 ohm impedance will be fine for a 40 ohm cartridge, or a 30 ohm cartridge such as the one owned by the OP. So there is nothing about this that is different from what I have been saying. If he had a 3 ohm internal impedance cartridge, the transformer can provide a 1 to 33 gain ratio. Bur the 3 ohm inputs should obviously not be used with his cartridge because the 1:33 turns ratio results in a less than 47 ohm impedance for his 30 ohm cartridge. In that scenario about half the cartridge output is lost to ground and for other reasons there would be loss of treble.

Dear Raul, please reread my post. Transformers have no impedance per se. My point is that with the peculiar nature of this cartridge, having a low output and a high internal resistance, the choices of gain ratio are limited to around 1 to 10 or may be a little higher, if one wants to observe the rule of thumb about impedance matching. Of course, one is always free to ignore that principle. But if you choose to use a higher gain ratio transformer, then you will be wasting some of the already very low cartridge output. It’s like chasing your tail.

Which is why it would be useful to know what phono and linestage the OP uses.

Because MM phono stages vary quite a bit in the amount of phono gain they provide, from 39db for the Ypsilon to 50db for the Manley Steelhead, just to name two extreme examples. Then there is the fact that the OP wants to amplify a cartridge that puts out 0.2mV and has an internal resistance of 30 ohms. Those two parameters suggest he is limited to a SUT that provides 10X gain, a 1:10 turns ratio, IF one wants to observe the rule of thumb that says the phono input impedance should be 10X or better in value than the internal resistance of the cartridge. Assuming a 47K phono load resistor, a 1:10 SUT will have the cartridge seeing a 470 ohm load. That’s fine, but as soon as you go to higher gain SUTs (higher turns ratios), the impedance seen by the cartridge will fall way below the ideal, in terms of its ability to drive the phono input. For example, a 1:20 SUT will give a load of slightly more than 100 ohms. A 30-ohm output Z is driving a ~100 ohm input Z. In that case you need enough gain to overcome the fraction of cartridge output that will be lost to ground, because of the relative impedance mismatch. So, in short, seems to me you want an MM phono stage with relatively high gain, as MM stages go, because ideally you don’t want to have to use a SUT with much more than a 1:10 turns ratio. Of course, the OP needs to take into account the additional gain of his linestage, as well, which could ameliorate the potential problem.

I should finally make clear that there is nothing magical about the 1:10 output to input impedance ratio. The fraction of signal voltage that is lost to ground increases linearly as the ratio gets closer to 1:1. Even the 1:10 ratio does not result in perfect efficiency; signal voltage transfer is a bit better than 90% at that ratio.

Once one knows the phono gain and the linestage gain, and perhaps the input sensitivity of the amplifiers, then one can decide whether a 1:10 SUT would be sufficient.

What phono stage?