Installed new cart......taming the hiss......

Yesterday an audio bud re-installed my Dtna 20L and we set the Musical Surroundings Phonomena stage aswell.With my old MM AT cart I had a slight hum, like a bad ground but not bad enough to worry about but now I have a hiss I want to get rid of, its set at 60db gain and 304Ohm I think. What should I adjust and to what value to tame this down, I think it may drop back if gain is lowered but then the CDP volume will be far higher causing potential brainfarts to damge speakers when switching back and forth, Thanks for any ideas Chad
I am using a Shelter 501 MKII on a Rega 300 arm and the Phonomena stage. I have used every gain setting on the Phonomena because I am recording my vinyl and want to get the loudest signal w/o clipping and have never heard any hissing or hum. The only time I hear any noise is when I turn the volume up way past what I would listen to.

The only suggestion that I can offer is to move your phono stage and see if that helps and try to plug it into a different line.

Check to make sure the cartridge posts are properly seated into the leads coming from the tonearm cable, and that the rubber shielding is slid all the way down over the leads. It must be perfectly snug. I have had this problem twice, and both times it was the headshell leads not being properly connected.
Thanks guys, I will check it all out.