Should I use an external Phono Preamp

In another thread, OP found a power cord near his phono cable was causing hum, it’s worth moving wires and seeing if anything changes

L only?

R only?

Your McIntosh has two inputs, try them both, (make sure both inputs are configured for your cartridge) verify the hum exists on both inputs, that should eliminate the McIntosh itself (not totally, but move on).

Too much gain chosen on your McIntosh? Try a lower gain, see if you still get enough volume when playing an LP. Hum less or gone?

ground

cable connections

headshell/cartridge wires

another headshell with a different cartridge?

If you don’t have one, or a friend cannot bring his over, like your Ortofon, this is also Shibata on Boron, only $429, including the headshell. MM with replaceable stylus.

https://www.audio-technica.com/en-us/cartridges/type/moving-magnet/at-vm750xsh-h

Minimum cost, $110, with headshell would prove it was not the cartridge, and leave you an elliptical on aluminum to play old LPs or nothing special audibly with (i.e. not wear out your good stylus on not so special lps).

You could keep the headshell and sell the cartridge with 1 minute play.

https://www.audio-technica.com/en-us/cartridges/type/moving-magnet/at-vm95e-h

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