I've had similar experience since going from an old ARC PH3SE to the new Herron last year. Keith assures me its not the Herron and I believe him. Especially since the noise definitely does change when I mess with the phono leads. Not sure why its more of a problem with the Herron than it was with the ARC. But it does reinforce my experience with phono stages which is that even the best of them are the most temperamental and idiosyncratic of all components. With the possible exception of step-up transformers!
In my case, while the noise definitely is a lot more than I get from any other input still it is just barely at audible level from the listening chair and in any case less than groove noise from all but a few of the most silent pressings. Which is why in the big scheme of things it is way down on my list of things to work on.
Early on it was much worse though. So it is probably something you can reduce if its that big a priority.
Things that helped for me, including some suggested by Keith:
Clean everything with alcohol. Just plain alcohol and a clean cloth. No contact conditioners.
Experiment with phono lead routing. Sometimes they like being together, sometimes apart, and sometimes even a small change makes a difference. I use Scotch tape once I get them where I want.
You can make your own shielding from battery grounding strap. Its actually a mesh tube that can be slid right over the interconnect. If you think this might help you can test it out first by wrapping aluminum foil, just tear into strips and wrap, being sure to go all the way to the end of the RCA.
RFI could be a problem, anything could be the source, flip off breakers to everything, unplug everything, then reconnect/power on one thing at a time.
Static electricity is a problem. Mine isn't bad enough to make white noise but it definitely affects the sound. Static-Guard anti-static spray for laundry works great. $3 at Walmart. Don't spray right over a record but do waft it around the turntable and over all cables. Do it right before playing a side.
When I did all this stuff and still had a problem my last ditch effort was to replace the RCAs. Went to solder new ones and it turned out there was a bad solder connection! Not likely what you have but you get the idea, all you can do is check and check and check until you find it.
