Phono Preamp Gain


Hi all,

I am in the process of getting a new cartridge and I want to make sure the output voltage is a good fit for my system. First off here's what I'm working with:

VPI Prime
Schiit Mani (30dB, 42dB, 48dB, 59dB gain options)
Prima Luna Dialogue Premium Integrated (239mV input sensitivity using KT88 tubes) (S/N ratio 81)
JBL L100

My question is what do I use for Vout in this equation to calculate the correct gain to choose on the Schiit Mani phono preamp??


20log(Vout/Vin)


Using the input sensitivity of the integrated and the output voltage of the  Soundsmith Otello ES Moving Iron Cartridge I get 

20log(.239V/.00212V) = 41dB gain

Is this correct?
My main issue is I dont know if my assumption to use .239V is correct.

Cheers



nmo25
Tablejockey,

Of course! I wanted to see if I was in the right ballpark before messing around and finding out what sounds best. I haven’t bought the soundmith cart yet, but the compliance works well with the lighter VPI arm so my next bet was to see if the output would be close to one of the gains on the mani. 

Obviously my phono stage is the bottleneck in the system, and eventually I would like to upgrade that. I appreciate the tube preamp recommendations because that’s definitely the path I’ll be going down. I’m not sure if the JBLs are anywhat of a good match for the Primaluna but I got them for dirt cheap at an estate sale so they are staying for a while. 


You don't really need to worry about any math equations, because you have a combination that cannot fail to provide enough gain up the chain, and because you cannot damage anything by experimentation. But if you insist, there are excellent calculators for converting signal voltage to db and vice-versa, on the internet.  There may  be one on the KAB website, for example.  For what it's worth, I am running an MI cartridge with output similar to that of your cartridge into a Manley Steelhead, with no added gain downstream from any linestage.  I find the 55 db setting on the Steelhead works fine.  My amplifiers seem to have a very high input sensitivity (meaning, full output is achieved with much less than 1V input), which helps. In your case, because you do have an active linestage section that adds 12db, according to others who posted here, probably 48 or 50db is a good choice.
I tried all the recommended MM levels on my Schiit Mani and Freya with a Grado MM. Two levels sounded good. One was a better match for being similar to my digital rigs channel, so I'm using that. (I should note there was a distortion before the unit and cables burned in, so if yours is a new set up, do a burn in on the Mani).
"I’m not sure if the JBLs are anywhat of a good match for the Primaluna but I got them for dirt cheap at an estate sale so they are staying for a while."

nmo25- I bet the JBL's will sound good, if you like the "vintage sound"

Vintage sound to me is not overly detailed, overall presentation leaning on the warm side. There shouldn't be any lack of bass with the JBL's.

You might be able to fine tune the JBL's tone with the 2 gain tubes on the PL.


@tablejockey re: "There shouldn't be any lack of bass with the JBL's." You might want to edit that to say 'mid-bass' as the L100 starts rolling off steeply around 55Hz. It's also a high-Q design with a peak of 6dB or more so an octave above the port tuning frequency. Low bass was never a capability.