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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
dover
2,368 posts
 

@atmasphere 

Any brightness is usually not the fault of the cartridge so loading will not fix it. IOW If loading does fix the brightness, the cartridge wasn't the problem.

The phono section is.

This is because any LOMC cartridge generates RFI due to the cartridge's very low inductance, in parallel with the tonearm cable capacitance. That sets up an RF peak (usually 1-5MHz) which can oscillate, generating RFI up to 30dB higher than the cartridge signal level, injected directly into the phono section input! 

Whilst I agree with your statement, both the Decca and Soundsmith are MI, not MC.

Therefore loading changes affect the frequency response ( and phase ) to a far larger degree than a LOMC, and as far as I know the frequency changes with MI from both resistive and capacitive occur within the audible range. Is that not correct ?

dogberry OP
827 posts
 

I cannot hear any change with various capacitative loadings. Maybe others can!

rsf507
2,472 posts
 

I say trust your own ears 👂

atmasphere's avatar
atmasphere
12,200 posts
 

Whilst I agree with your statement, both the Decca and Soundsmith are MI, not MC.

Therefore loading changes affect the frequency response ( and phase ) to a far larger degree than a LOMC, and as far as I know the frequency changes with MI from both resistive and capacitive occur within the audible range. Is that not correct ?

@dover That is not correct. 

The means of the magnetic device isn't important. The inductance is. The SS is fairly low inductance (hence low output) so everything I said about loading applies to it. 

You are correct in implying there is a continuum. The more inductance the mechanism employs, the lower the resonant electrical frequency with the tonearm cable. High output MM cartridges have such high inductance that the electrical peak is at the extreme high end of the audio band or just barely ultrasonic. Usually because the coil used is also lower Q (Quality; the relationship between its length vs its diameter) the peak is less profound and covering a wider range of frequencies. So a high output MM cartridge might have a peak of only 20dB (which is still a lot). That peak can affect the audio band directly so loading a MM cartridge is mandatory if you want it to sound right. 

 

dover
2,368 posts
 

@atmasphere 

Thanks. I have run the low output through Soundsmith's own phono and changes from say 800 to 1000 ohms with that phono were quite audible. You are saying this is the phono or phono/cable combo.

Decca is another story but I have set up probably north of 30-40 over the years - usually run at around 22k.

Thank you for the explanation.

 

 

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