SUT - electrical theory and practical experience

lewm

I wanted OP to understand:

cartridge SUTs are PASSIVE, no need to plug them in. And that they boost signal strength by themselves, i.e. boost, not ’enhance’ the signal.

Step Up or Step Down NEED to be plugged in to wall outlets. They also boost/cut voltages and do not enhance signals.

And a Cartridge SUT is working on a phono cartridge signal that goes into the preamp/amp/speaker system

A Step Up/ Down Voltage converter has nothing to do with the audio signal, just proper voltage to the motor.

Of course to alter AC line voltage a step down transformer of the kind you own must be inserted into the AC line. That’s precisely analogous to inserting a SUT between a cartridge and an MM phono stage in order for it to do its work. Both are passive devices. You implied that your step down is per se dependent on AC for power. I hope the difference is clear.

Dear @drbond  : " Does the SUT theoretically enhance or degrade the sound quality?  What does the SUT actually do to the sound quality?  "

First any device where the signal must pass degrades the sound quality, so the SUT degrades the signal quality and there is no way no matters what that that SUT could enhance the audio signal.

Today SUT's exist because there are tubes phono stages and even that exist 2-3 all tube high gain active units those are not the best solution for LOMC cartridges.

A SUT is not a passive device because any audio signal passing trhough those transformers makes that the " hundreds " of meters on each transformer react to that signal and starts the degradation and you have to think that the signal has a " long trip " inside each transformer wires and at each mm. the audio signal is degrading by that SUT. 

In the other side a good SS active high gain design say ith bipolar  active devices the signal must pass only trhough a matched pair of transistors in that first critical gain stage and degradation is at minimum way lower that in a SUT.

Advantage of a SUT: NONE. SUT develops or could be contaminated with some kind of " noise/colorations " and yes its frequency response is way limited and not only that: everything the same the badwindth, noise levels, THD, deeper bass, etc, etc belongs to the SS active high gain.

You can ask for measured frequency response and the like to any today builder to confim all what I mentioned.

I owned and still own SUTs and the only one that I listen time to time is the Denon 

AU-1000 modified by me where that SUT only sees a connector when in the MM phono stage. This Denon measured FR is: 5hz to 200khz, that's exceptional for any SUT and I admit that my modified unit puts the level degradation ower that any other SUT I experienced but not even my SS Essential 3180 phonolinepreamp.

There are several SS active high gain phono stages and normally are expensive ones as FM Acoustics or CH or the Channel D Seta L20 but exist very low price as 2.5K only SS units that makes a formidable job. Here one of those unit reviewed by MF and compared against Dartzeel and other way $$$$$ phono stages:

Today top LOMC cartridges are really expensive and makes no sense at at all try to been mated with a SUT that as I said and no matter what will degrades that valuable cartridge signal.

For me that I'm a MUSIC lover the only  path is a SS active high gain phono stage but only an opinion.

Regards and enjoy the MUSIC,

R.

Raul, By "passive", I only mean that it does not require or consume external power.  OK?  You can use any other definition you want.

I’m a SUT + LOMC fan. I just like the sound many (most?) SUT’s provide - rich, meaty, weighty. In my system, that’s the right direction - other systems may differ. I have an Audio Research Reference 3SE with a really great JFET MC stage. In the past I’ve had a Herron VTPH-2A, also with a great JFET MC stage. These JFET stages sound great, BUT they’re inevitably leaner and more sterile sounding than the SUTs I like. I have about a dozen MCs, so my listening experience is not limited to 1 or 2 models.

That said, there’s a pretty great variance in the sonics of different SUT brands. The difference can be as significant as changing cartridge brands, even when the step-up ratio is kept close. It’s quite striking. The blue-label CineMags (this includes Bob’s Devices Sky, 1131, 1254) are very much on the rich/lush/weighty side of things. The EAR has a particularly romantic tube-like midrange. The Quadratic MC-1 (a CineMag blue but with a MUCH bigger core than usual) has extremely low distortion through the midrange and treble with extremely powerful bass response. The Hashimoto and Koetsu are also excellent, and a bit more neutral, though still with more weight than a JFET. The Lundahl LL1931 and LL1931Ag (amorphous core) is much thinner and more "crystalline" sounding - not a bad sounding SUT, but not my personal preference! I think I actually prefer the JFET stages to these. Also - don’t skimp with a cheap SUT; I found the Red-label CineMag 3440A (cheaper than and blue-label) to be borderline bad, and the Lundhal LL9206 (cheaper than LL1931) to be fairly mediocre.

One practical consideration is you really need a very short, low capacitance run of cable from SUT to phono stage. If not, you’re going to REALLY hear this cable, in a bad way. And a 20x step-up ratio is usually a "pretty good" choice for many/most LOMC cartridges.

I’ve found a good SUT will be quieter than a good JFET stage IF (!!) you can properly address all grounding gremlins.