SUT Advice - Which Ones Are The Best?

Edgeware, I am puzzling over your saying ..."the Denon has only 21dB gain and not suitable for low impedance cartridges,..." First, 21 db of gain equates to a voltage gain of about 11-fold. So, it would provide more than adequate voltage gain for any LOMC with at least 0.4 to 0.5mV output, to drive a typical MM phono circuit with at least 40db of intrinsic gain. I don’t understand why you say it is not suitable for cartridges with low internal impedance, unless you know something about the inductance of the primary winding of the Denon, per the post by JCarr. With a typical MM input providing a 47K ohm load resistance, this Denon SUT would present the cartridge with about a 400 ohm load. Certainly that is OK for any LOMC, notwithstanding the issue of primary inductance. I actually think there is a bit too much hocus pocus surrounding the mating of a SUT to a cartridge on one side and the phono stage on the other. What you need to worry about is the voltage gain, which is related to the turns ratio of the SUT, the impedance seen by the cartridge, which needs to be about 10X or any ratio greater than 10X that of the internal resistance of the cartridge, and the inductance of the primary. Keep in mind also that a transformer essentially has NO impedance of its own; it only reflects an impedance from whatever is hooked to the secondaries back to whatever is hooked to the primaries, and vice-versa. In my opinion, the old custom of rating SUTs in "ohms" seems to be very confusing to a lot of people and really should be abandoned because it is not even informative. And finally, using a SUT gives up current in direct proportion to the voltage gain it affords. The product (voltage X current) is a constant on one side vs the other. If V goes up 10X, then current goes down 10X.

Mijo, Why are your wanting me to read about Sowter SUTs?

@lewm I probably should have refrained from making that statement, but allow me to explain where it came from. Most low impedance, low output MC's I use (various Ortofon's including SPU, FR7, Ikeda 9, Miyabi, etc.) have between 0.2 and 0.3 mV output. My MM phono input stage has 40dB gain, so using a 20dB SUT (or 21 in the case of the Denon) would bring the total gain to 60dB. I have tried several SUT's with 20dB gain in my system (but obviously not this Denon) and in all cases and at the same volume level these low output MC's sound more alive and musical using a SUT with 30dB gain (like the Entré ET-200 and Ortofon T-3000 I'm using now).

The specified impedance is perhaps less significant, but I've tried some of these low impedance cartridges with SUT's that offer switching between low (usually 3 ohms) and high impedance (20-40dB). To my ears using the high impedance setting on low impedance MC's sounds much inferior to the 'correct' setting, of course with the appropriate correction of the volume control.

That's what I've learned from making these comparisons. So, when Denon specifies 21dB gain and 10-40 ohms impedance range for the AU-1000 model,  I'm inclined to think that this will not be the best choice for the cartridges I like. Perhaps the Denon flies in the face of that and I won't deny that possibility until I hear it myself.

I was looking at SUT’s a few months ago. I ended up contacting Andrew Rothwell at Rothwell Audio UK. He offers a range if his own SUT’s. He made it clear that it was essential to ensure that any SUT selected should suit both the cartridge and phono-stage it would be used with.
i ended up purchasing the Rothwell MCL with 26db of gain. My phono-stage on the MM side had quite a low 36db of gain, so combined this gives me 62db of gain overall. That pretty much matched the 62db of gain from the MC side of my phono-stage.

i have been very pleased with the MCL and the performance from it. I was also very impressed by the helpful advice that I received from Andrew in helping me decide. 

Dear @keswick : If you can try to change the default PS MM 47 impedance by 100k.  
If your system has the adequated resolution you will listen the benefits on that change.

R.

Hi raulinuegas 
Thanks  for your advice.
i am currently running a DV 20x2L via my SUT and the MM side of my phono-stage. Unfortunately my phono-stage only has one fixed setting for MC and another for MM cartridges, so I am unable to alter it. So until I ever get around to upgrading the phono-stage for one that is adjustable I will have to live with what I have. Having said that, it does indeed sound very good as it is.
What benefit would changing from 47k to 100k actually bring for my current cartridge do you think, or were you thinking that Ivwa# running a Koetsu ?