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Which SUT to match Koetsu Rosewood Standard in my system?

Howdy everyone,

I’m about to move to to my first MC cartridge, and I’d be grateful for your advice in choosing a step-up transformer. First, here’s my current system:

  • Table: Thorens TD-124 (mk I, with a few upgrades from Hanze HiFi)
  • Arm: Ortofon TA-110
  • Cartridge: AT-540ML
  • Amp: Audio Note Soro Phono SE Signature
  • Phono stage: Built-in MC phono preamp in the Audio Note Soro
  • Speakers: Klipsch Forte IV
  • Interconnects: Ortofon 6NX-TSW-1010L (came with the tone arm)
  • Speaker cables: 14 gauge Audio Note bulk wire (planning to upgrade this at some point, but not until I finalize the analog front end)
  • Room: I live in a city townhouse, so my listening room isn’t huge—about 15 feet long by 12 feet wide. It has been sound treated a bit: absorption at the first reflection points, front corners, and on the ceiling slightly in front of the listening position, and diffusion + absorption along the back wall.

It seems to me that the clear mismatch now is the cartridge, and after auditioning several contenders, I’ve settled on the Koetsu Rosewood Standard. At least in my system and to me ears, it gives me the most of what I want: a rich, organic, natural sound. When I auditioned it, the dealer lent me an Audio Note AN-S8 SUT. A fantastic piece of gear, but well above my budget at this stage.

So I need some help choosing an SUT. Here are a few priorities:

  • Maximizing the natural, organic sound of the Koetsu and amplifier, which seems to balance so well with my speakers—retaining the dynamism and drive of high-efficiency horns while taming stridency that sometimes also comes along, especially in my relatively small space.
  • Favor emotional impact over technical accuracy: “good” distortion can be fine with me.
  • That said, minimize noise. I rent a city townhouse, so there’s old wiring that I can do only so much to fix, and a healthy bit of RF noise. My turntable, while about as quiet as an idler wheel can be, isn’t as quiet as the best designs of today. My amp is great, but also not silent. And at 99 db sensitivity, those horns pick up everything. So it’s important that the SUT be well shielded from RF noise and have an effective grounding scheme.
  • Favor an ideal match with cartridge, amp, speakers, etc. rather than future flexibility. I don’t mind swapping the SUT out for something else if I decide to change cartridges sometime in the future. I prefer optimizing it to what I have now, not what I might have
  • A 1:8 step up ratio, if possible. The cartridge is 0.4mv; the amp’s phono input is 3mv. 
  • Budget: $3k or less, ideally 

I really look forward to your thoughts. Please don’t hesitate to ask for any other info that might be helpful. Thank you!

zazu22
mulveling's avatar
mulveling
1,913 posts
 

The step up ratio needed for any pairing is system dependent. What someone else “likes” in terms of turns ratio is moot. Furthermore it seems Mulv has platinum magnet Koetsus, which would give the lower voltage output he quoted, 0.3mV. In that case, and depending upon the downstream equipment, I could see using 1:20. But the Rosewood makes more output voltage than any platinum magnet Koetsu. Certainly more than 0.3mV.

@lewm  It's really not THAT system dependent with Koetsus. There's only so much output range in the lineup. I have a non-Platinum Onyx in my collection and while I don't have a spec on it (maybe an Onyx Signature or Gold from the late 80s / early 90s; had it rebuilt by Koetsu 3 years ago retaining the original magnets), if anything if "seems" like a bit more than 0.4mV compared to the 0.3mV Platinums (which are quite consistent among themselves). Since its magnet is small (modern short body), it must be samarium-cobalt or permendur like the current 0.4mV line.

Anyways this non-Platinum Onyx works fantastic with 15x - 20x. ~20x is a good ratio for all Koetsus. 1. Very effective at keeping noise floor down to a minimum (from the active gain parts of your phono stage). 2. If your stage has decent overload margins at all it won't cause a problem there, and 3. Phono stage is upstream from line-stage volume control so that protects the downstream from overload conditions and you just adjust volume to your preference. 

lewm
13,108 posts
 

The numbers say a 1:10 SUT will likely work. This means 1:20 and anything in between will also work. If overload would be a problem at 1:20, that’s a poor design, which is to say I don’t think it’s a problem. It’s all good.

zazu22 OP
9 posts
 

Thanks for all the recommendations and advice. Now to see who out here on the west coast might have some of these options to audition. 

jperry
2,450 posts
 

Auditioning some of the options will be difficult.

I would just buy a used Koetsu SUT, then sell if you don't like it.

pindac's avatar
pindac
2,864 posts
 

I had been demonstrated many SUT's over the years. I have even been very impressed with my last demo's that took place in 2022.

Prior to the 2022 demo's a selection of models have been immediately repelled, as the sonic was far too overbearing for my tastes.

If I want a taste of how it feels to trudge through the Bass Notes, I can route one of my MC's through the MM Stage, usually only done for a demonstration, but it certainly becomes overwhelmingly bloated presentation.

It is a good practice to be patient and have a few experiences to get a idea of how differing devices will interface with a set up, and decide on the Rich Tones that will be present, being at a level that are attractive to ones preferences and would be wanted to be maintained.

If a Phon' is at hand, that will enable the MC to be used, the SUT selection can be carried out with a inquisitiveness and a careful approach.

 

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