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Impedance Loading for SS Hyperion

"470 - 1000Ω" says Peter Ledermann. My phono stage offers 400. 800, 1,200. so I used 400 initially (extremely smooth), decided 800 was better (some edge present) and 1.2k even better still. There is one higher setting allowed for the MC input (along with several lower ones), 47k. So I’m trying it, and I like it. I keep swapping to the London Reference I am comparing the Hyperion to, and it seems the higher the impedance loading, the closer they sound. I am not experiencing the "peaked high end" I was warned of if loading is increased over 1000Ω.

Maybe my half a remaining ear (thanks, streptomycin!) simply can’t hear the cartridge screeching. Might work for others with high frequency loss? I think the issue is that I have a powered sub that is making sure I hear some bass whatever the loading is set to. If I turn it off the Quad 2905 speakers alone don't sound as if I'm listening to the full range of sound. Perhaps I should set the loading without the sub, and then do my usual procedure of setting the sub volume so I cannot tell that it is switched on, but all the same things sound better?

dogberry
billstevenson
509 posts
 

Yes with my Consolidated 10:1 it would be 470, with my Bob's devices 5:1 it is  1,880.  With no SUT it is 47,0000.  My phono stage works any of these.  

lewm
13,508 posts
 

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.

intactaudio
306 posts
 

@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

lewm
13,508 posts
 

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.

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