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Does my phono stage have sufficient gain?

I am considering a ZYX UNIverse for my Granham Phantom Mkii/VPI TNT Mk IV rig. I use the EAR MC-4 SUT with a tube phono stage run in MM mode. I would prefer the LOMC UNIverse at 0.24mV output and 4 ohm internal impedance from what I have heard and read.

Do I have enough gain? Here my reasoning:

* EAR MC-4 SUT has four taps. Using the 3 ohm tap is 30x input or 7.2mV; I have been told that each 10x of an SUT roughly equates to 20 dB, so 30x equals 60 dB??? There is a 6 ohm tap at 24x (or 48 db???)
* The MM mode of my tube phone stage provides 37 dB gain
* My line stage using XLR out is 18 dB

Am I thinking clearly?

Thanks.
flyfish2002

Showing 2 responses by dougdeacon

dougdeacon
3,338 posts
 
ZYX did not use the industry standard test record when they measured that .24mv output spec. A LO ZYX's output using the industry standard record is ~1.41x higher, so ~.34mv.

Redoing the calculation above for .~34mv yields ~5.7 volts before the power amp inputs, which presumably is sufficient.

Whether the 3 ohm tap on the EAR will provide a suitable impedance for a LO UNIverse is a whole other question. If not, frequency balance in the highs may be off.

More generally, the EAR and Sonic Frontiers phono and line stages are not really capable of reproducing everything a UNIverse will send them. Not saying it won't sound great, it probably will, but be aware that you'll still be missing quite a bit. To that extent this is a slightly risky choice of upgrades.

OTOH, the remaining UNIVerses are such a bargain it's hard to resist, even though upgrading your phono and line amplification before attempting a top tier cartridge would normally be preferable. But top tier phono and line amplification would cost at least 3X the price of a UNIverse, so this might be a good time to break that "rule".

Enjoy!
dougdeacon
3,338 posts
 
Brent,
I missed the fact that you've had your SF gear upgraded. Very sorry. Of course I withdraw everything I said about it since I haven't heard yours. Higher quality caps and power supply improvements would, IME with other preamps, make a dramatic difference.

That said, $10K+ is indeed the price of admission to the 2 or 3 best phono/line stages I've heard, and even that doesn't necessarily get you there. Not that you need to spend more, I just meant that I've heard many $10K and even $20K preamps that DON'T get you there. Your buy quality used and upgrade path makes great sense to me.

Unfortunately, with SUT's, about the only way to know if a particular LOMC will mate well is to try. You could always adust impedance with resistors either on the primary, the secondary or both. That's a lengthy process needing many resistors of many types to find the optimal setup. Been there, did that, much prefer the ease and sound quality from my high gain LOMC section. YMMV of course, especially with something as complex as impedance matching with an SUT.
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