Should I use an external Phono Preamp

Both channels. It does increase with more gain or more volume. 

Understanding Hum, especially caused by earth loop and who knows what other loops or anomalies between Power Supply and signal circuits across devices. Is a subject and interrogation, I know only two people who are I  would be able to trust to correctly trouble shoot shoot a issue discovered. 

I really hope for all who may have a issue, the fix proves simple. 

lewm,

I had to go back and look at what I wrote.  I deny making the categorical claim that all external phono stages outperform built-in phono stages.  Clearly that would not be wise.  What I said was that excellent phono stages outperform built-in ones and that is a statement that is generally correct.  In the present case there is doubt because both phono stages have been tested and reviewed and are highly praised.  The only way to know which is better would be to directly compare them.  Based on having heard both the Mac and the Luxman EQ-500, I am pretty confident that the E-07 is better, the question is by how much and is the price worth the gain?  And that only the OP can answer.  Back to the matter of external phono stages, the limitations you outline are accurate of course.  It is important that the phono cables used on both inlet and outlet be of high quality and kept as short as possible.  I recommend 0.7 m - 1.2 m maximum length.

@mooks005 

hum can be caused by the following 

1. turntable interconnects close to a source of EMI/RFI (power cords, power transformers, routers, mesh network nodes, wifi extenders, etc.)

2. Tonearm ground cable not connected to preamp chassis

3. Preamp not on the same circuit with amplifier. This can create ground loop and that will present as hum

The E07 costs $6500 in the US. Hardly an amount of money that most of us can spend on an experiment. Perhaps borrow one from a dealer makes sense. Bill, I’ll dig up your words but I do think you made a categorical statement re the inherent superiority of phono stages vs phonolinepreamps. Anyway, no big deal. The two very best phonos I’ve heard and own are both phonolinepreamps, albeit one of them was heavily modified by me. Three if you count the Manley Steelhead which has an active buffer linestage that adds no gain. My opinion is to just find the phono you like without bias in favor of separate components. As you know there was a time when the word “preamplifier” meant a component that contained both line and phono. Then along came the temporary demise of vinyl and manufacturers found a way to make money by separating the functions.