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Do I need a sut?

I purchased an Ortofon MC2000 cart from a fellow A'Goner, it is very low output .05mV, my phono pre is a Herron VTPH-2 which has 69db of gain and my pre is a Herron VTSP-3a(r02) 14db gain.
The cart sounds wonderful, but with such a low gain I have to turn up the volume by quite a lot. If I had, another source at that volume, I wouldn't be able to stand it. With the volume turned up so high I get a fair amount of noise between tracks. 
Should I be looking at an sut or just live with it the way it is? I found an Ortofon at a decent price, it has 24db of gain. Would that be ok to go into the mc input on the VTPH-2? The mm gain is 48db, if I plugged it in there I would only gain 3db(if I'm doing my math correctly) I will also be contacting Keith, but I thought I would ask here too.
Thanks
Jeff
jdodmead
jdodmead OP
241 posts
 
My amps are Herron M1A mono's
Output Power150 watts @ 8 ohms, 275 watts @ 4 ohms (measurements at 1 khz)
Gain24 db
Input impedance220k Ohms
almarg's avatar
almarg
8,673 posts
 
150 watts into 8 ohms corresponds to about 34.6 volts. 24 db less than that is about 2.18 volts. 2.18 volts divided by 0.05 mv is a voltage multiplication of 43,600 times, which is about 93 db.

So to be able to drive the amp to full power when the cartridge provides its rated output you need a total of 93 db of gain between the cartridge and the input to the power amp. For that to be accomplished with the MM section of the phono stage providing 48 db and the line stage preamp providing 14 db, the SUT would have to provide 31 db (or more). Exactly mid-way between the value Hdm suggested and the value Folkfreak suggested :-)

Regards,
-- Al
jdodmead OP
241 posts
 
So the XG-5  should work for me.

jdodmead OP
241 posts
 
There are in and out ground lugs on the XG-5, would I be ok if I just went straight to the Herron phono pre with the output ground from the turntable? 

Thanks
Jeff
folkfreak's avatar
folkfreak
1,149 posts
 
@jdodmead regarding grounding I'd start by connecting the phono ground to the SUT and see how that sounds -- really it's a matter of checking what sounds best (most open and "solid") with least hum -- it may be the SUT, or leaving it unconnected. I'd be surprised if grounding to the phono stage rather than the SUT is best -- in fact it may induce a hum

If after all this you still get hum (and after trying moving the SUT around and away from transformers and power cords) you may need a more sophisticated SUT with a ground lift option. I'd be surprised however if you have these issues with an Ortofon -- I only have hum issues with my mono cartridge (which is another set of problems)
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