is th gain on my phono preamp enough for MCoil?

My  tube phono preamp provides 52 db gain on the MC input.With the preamp switched on I do hear  a  very slight buzz/shhh  when the volume on my main integrated amp is in its normal 9-10 pm position. I assume this is circuit noise or just tube noise. When music is playing this is lost in  background but it does worry me since there is no complete silence on quiet passages.
My  shelter MC cartridge put out  0.5 mv. I am wondering if the gain of 52 db is enough since it means I cannot turn down the volume on the main amp to decrease the noise from the preamp. What to do since I like all my components.??
52 db is a suboptimal match for your 0.5 mV Shelter, since it place the signal too far down towards the noise floor. By the time you raise your amp volume to compensate, audible hum & noise is the inevitable result. At 52 db it's really too low to call a proper MC input, since that only matches well with the highest output MC's.

On the other hand, 52 db is very high for an MM stage, thus limiting its options for SUTs. So it's a little bit in no-man's land (other than high output MC's). However if the overload margin is good on that MC input, and it can be set to 47K loading, then you might significantly improve sound with e.g. a 1:10 Bob's Devices Sky SUT into your phono stage. I have a 1:20 Sky and Shelter Harmony (also 0.5mV) into a 44db/47K phono stage, with great results. You'd have a total of 72 dB gain with a 1:10, which isn't too bad because now you'd be turning the amp volume DOWN to push down the noise floor (with signal riding MUCH higher above this floor). Also, a Lundhal 1131 or 1141 at 1:8 or 1:16 gives great results with my Shelter. The Sky renders a meatier, fuller sound with great slam, and the Lundahl is more delicate and airy. Pick your poison!
With 52dB, the sound will be somewhat castrated. 
+1 mulveling!
Lundahl makes MC transformers that are 1+1  ;; 8+8. Wired for a gain of 8 times that's a gain of 18dB for a total of 70dB or 4mV output with your Shelter cart. K&K Audio sells a kit with a case and PC board and RCA jacks for a reasonable price.