To make it a bit simpler, you’re probably OK with a SUT that enhances the signal voltage by 10X. In other words, a turns ratio of 1:10. It is unpardonable that the manual doesn’t stipulate phono gain but we can hope it’s at least 40db. We do know the fixed phono load resistance is 47K ohms. For a 1:10 SUT this means your cartridge will see a load of 470 ohms. (Load seen by cartridge = 47K/(turns ratio)-squared = 47K/100 = 470.) over the decades, I have seen output voltage for the Rosewood quoted between 0.4 and 0.6mV. Other important variables and unknowns include linestage gain and amplifier input sensitivity and speaker efficiency.
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!
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- 33 posts total
Thanks for all of the advice so far. I’ll reach out to Audio Note to see if they’ll provide that info. One other piece of potentially relevant info: I do have the Hegel V10. Would it be useful to play around with gain and capacitance settings on that first, and see what works best? I just wasn’t sure if the combination that might sound best on the Hegel would necessarily translate to what would sound best on an SUT. |
@lewm on the question you asked:
The Audio Note manual says that line level input efficiency is 300mv, and line level input impedance is 100 Ohm. I’ll report back on gain. As for speaker efficiency, it’s 99 dB. Thanks. |
- 33 posts total