Hello Mulvening,
I just went through this recently when I purchased a (new-to-me) Herron phono stage (I couldn't resist when it came up for sale recently).
After getting it installed, I was having the same issues you are having. I spoke to Keith Herron about it,asking him about adding a resistor to knock those low frequencies out that are causing the problem. He talked me out of adding a resistor in the phono stage (which I had done on my Modwright) and just using an equalizer to get those low frequencies out.
I ordered a Schitt Lokius unit, and even though it's inexpensive, is a very good little unit, absolutely quiet. I can recceommend it if your fix is involved around doing what I I wound up doing.
Love the Herron, by the way. Regards,
Dan