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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
2,036 posts
 

For Koetsus I like the Koetsu SUT best, followed by the EAR MC-3 / MC-4. But the CineMag / Bob’s Devices 1254 / 1131 / Sky models are also excellent for the money -- musical and fun to listen to. The EAR’s have a 10x tap but for my 0.3mV Koetsus (I have more than a few) I find a ~ 20x ratio ideal. The 0.4mV level is ideal from ~ 15x - 20x. The 0.3mV will be fine even at a 30x ratio. Perhaps I like the higher ratios because it helps keep noise floor (from the phono stage) to a minimum. ** Higher SUT ratio won’t help with noise floor related to your sensitive horns, since you’ll have a downstream volume control in the line stage -- at that point noise floor is up to your line stage and amplifier having "not too much gain " plus a high signal-noise ratio. However, minimizing noise floor from the phono stage is certainly beneficial too :)

I don’t like the leaner and tonally "cleaner" sounding SUT’s like Lundahl LL1931. Hashimoto HM-7 are good, fairly neutral, but not my thing either. I prefer warmer, full-bodied sound SUT’s to showcase the true nature of Koetsus :)

The Quadratic MC-1 is an interesting option, though it’s a bit darker sounding which might push it too dark with Koetsu in some systems. Very powerful bass with clean & detailed midrange. If you look inside it's a CineMag blue label like 1131 / 1254 / Sky, but with large cores that are at least twice the size of those models :o 

pindac's avatar
pindac
2,864 posts
 

@mulveling Is from my reading Posts on this forums Analog Section, is one of most experienced SUT users. His descriptions of Tranx Windings I have experienced in use in my system are with a content that is almost identical to how I have a recollection of experiencing the Winding.

There is guidance in the previous post to help the OP get an idea, of how much of a Rich Tone they can add to the sonic, by creating a interface with a certain type of Brand of SUT.

I have a Hashimoto SUT and keep it at hand, as it the leanest of the owned SUT's. If I want a more lean sonic, adding a Head Amp in place of the SUT's works, the Head Amp in my assessment is able to present with a perception of leanness that is cleaner than a built in MC Stage on a owned Phon'.  .  

lewm
13,359 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.

mulveling's avatar
mulveling
2,036 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
13,359 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.

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