Choosing the right SUT for my setup



I’ve decided to add a SUT to my setup. My MC carts are a Denon 103R (14 ohms/0.25mV) and an Audio Technica AT-OC9XSL (12 ohms/.4mV). I’m trying to decide between two used SUTs: the Denon AU-300LC and the Denon AU-320, both having a 1:10 ratio. Would loading ideal gain for the 103R and the OC9 be best achieved thru a using a calculator and installing a resistor that can be switched for carts or testing with a trimpot then installing resistor? I’ve also seen writeups where the OC9 is put on a 1:12 SUT and 1:20 for the 103R; from the boards experience is that pushing overload, or its in a good spot?

jctyler

Guess it comes down to do what ever sounds good to you. I tried it both ways...sounds better with SUT in the chain. The extra cable is very low capacitance...makes no difference or detriment to sound. 

Also, I did not pull any of this from my A$$, WHAT I "assert" is fact. A good SUT will not add anything to the character of the sound. I disagree also about loading not being important. Too little or too much will effect both the high frequency response and the bass....that is why cartridge manufactures have a recommended load. 

@artemus_5 yeah, I have 2 SUT’s, same as those that have numerous amps (which I do) and speakers (own 5 pairs) and turntables (currently own 6).... different components do different things. I’m not about to unsolder resistors on a relatively new SUT...they are cheap enough just to buy the ones that will work for a specific cartridge...ie my Hana el and my eroica, both require something specific.

I also own a pro-ject Tube box ds2, whereas I can dial in Any load I want, however, it uses jfets to step up moving coils....not saying that’s bad, but generally not the best way to do it in my opinion. I would not say mc sounds bad through it, not at all...but with the SUT’S in the chain, to me they sound better.

The Tavish Design Adagio does. It right, they use Jensen transformers built into the mc section to step up the voltage. Nice, because it’s all in one neat chassis. You are aware that by using a SUT and running the cables into the moving magnet section of a tubed phono preamp uses the tubes to Full Effect?

When using the mc section of most tubed phono preamps, you are not hearing the full effect of the tubes, as confirmed by both pro ject and Tavish.

@artemus_5   It isn't a cut and dry question.  When using an active stage for MC with increased gain, one has to either design a separate preamp with added open loop gain or there will be a compromise between the two gains, that is, the gain for MM and the gain for MC.  This usually isn't an issue with selectable gains for MM, since the gain changes are usually small.   

Another issue is electronics add noise to the music signal with degrades the coherence of the music.  Granted, there isn't much we can do about that, after all, everything will get amplified sooner or later.   But the smaller the signal voltage, the more susceptible it is to noise degradation.   

I've designed preamps and some of them have had MC gain selection switches, so I am well aware of the issues here.   Granted there are good preamps out there with selectable gains for MC and MM, but for me, the SUT injects no electronic noise because it has none, which is a big advantage.   After that, it becomes which is a better design, so one cannot blanket statement and say SUT's are not as good as a preamp with selectable gains.   In many cases, the opposite is quite true.

Using a high quality passive SUT is the best way to step up a low output moving coil cartridge, run into the moving magnet section of a phono preamp, especially a tubed phono preamp, of which most use electronics to step up the voltage in mc mode. The exception being the Tavish Adagio and the Ear 834p (& I'm sure a few others) both of which use built in transformers to do the job.

Here is an excerpt from Jensen Tranformers website....

 

Once connected, the Jensen moving coil step-up transformer (SUT) is best described as a passive signal amplifier that does not color the tone or add artificial flavor. It is made for the purist. It does not try to impress with enhanced high frequency detail or exaggerated bass. It simply delivers the goods in its most transparent and natural form.