Impedance Loading for SS Hyperion

Because low output MI cartridges have much more inductance than comparable LOMC cartridges (as much as 1000X more inductance), 470 ohms is about as low as you want to go, which limits the typical system to using a 1:10 SUT where the SUT drives an MM stage with a 47K input Z.  This even though the SS and Grado LOMI cartridges have an internal resistance of 10 ohms or less. I'm sure Bill knows this, just saying.

@lewm 

Simply working the inductance against the load impedance is too simplistic of an assessment for the use of a SUT in the case of MI (or other high L ) cartridges.  What becomes more important is the load capacitance reflected through the transformer resonating with the inductance creating problems near the top of the audio band.  assuming a 1:10 and 150pF of load capacitance and 2.75mHy of inductance we get a resonance @ 25kHz.  The 47kΩ does a lot to damp this resonance but being so close to the top of the audio band makes me nervous.

dave

Dave, I hope I didn't claim to know exactly why inductance is the problem with using the SUT, only that it IS a problem.  I did understand it has something to do with HF resonance, but I guess I left open the incorrect interpretation that it has to do with the cartridge trying to drive the resulting load. Thank you for the explanation. I think Atmasphere has said the same. Based on reports here from users of the low output Soundsmith MI cartridges, Peter Ledermann is not against using SUTs with his cartridges but probably only ones with a turns ratio of 1:10 or less.

After having much frustration with 6922 tube noise in my Primaluna Evo 100 MC stage, both with tubes going noisy after a brief period, as well as the noticeable noise floor, I decided to hook up a SUP and run the phono in MM mode. For my Soundsmith Hyperion ES MK 2, I chose a set of Llundahl 9926 XLs, set to 1:10 ratio, that I installed in a project box. So, the loading works out to be 470 ohms. The result was nothing short of extraordinary - very low noise, excellent clarity, precise instrument positioning, vast soundstage depth, an overall a lot more realistic sounding. I do not perceive any dullness that would be fixed with higher loading. I had not heard what that cartridge could really do until now, and I’ve heard it through much more expensive fully active phono stages in my system. I can’t recommend this combination highly enough. I also think it’s a testament to the MM stage of that phono preamp. I do feel that the MC stage in it holds it back from its true potential, at least with my setup.

I used the Sussurro MkII ES with a VAS transformer (1:10) and enjoyed it greatly, and found no downside when I resurrected the NuVista Vinyl to using it with an input set to MC. So when I got the Hyperion I plugged it straight into the NuVista.

Prior to using SUT I had the Sussurro connected to an MC input of a Quad 24p, and that was not impressive (loading was fixed at 10Ω).

One strange thing to report, though, is that I recently had to swap in an old power amp (YBA-1ɑ) as one of my Quad II/forty amps developed a fault. The Hyperion now has a slight hum that I had not heard with the Quads. Irritating! I'm curious to see if it resolved when the Quad gets repaired.