Ghosting differences with 60hz supply

[grumpy]

In the topic about switching 16/32uF on the PI elsewhere in this forum I was interested to read some of the comments regarding ghosting with JTM45's
My JTM's both ghost, so does my DrZ Rt66(most over rated amp of all time). The thing is they all ghost the most around the same register, around the E to G on the B string with my amps. It happens a little elsewhere and I get a similar effect from my speakers around the 12th fret on B and E strings at high vol but that's not due to the amps.
Anyway back to the point. As I said I noticed that you 60Hz supply guys seem to get the ghosting more in the higher register compared to what I experience with a 50Hz supply.
It kind of makes sense to me that I get it worst around a G note because 50/100/200 Hz are all G notes, hence the 100Hz ripple sitting on the rails is superimposing a G on my output making the effect more pronounced (and unpleasant) when I play a note close to the ripple's frequency. From what I remember of my days at tech college when you modulate one signal with another, you get additional frequencys equal to the sum and difference of Freq1 and Freq2 and so on with the harmonics.
Any thoughts? Has anyone taken an amp and played it using different supply frequencies and noticed a difference? Anybody more knowledgable than myself on the theory? I'd love to read a thorough explanation of exactly what happens!
Incidently I don't notice the ghosting in a band context so it doesn't worry me, and I prefer the feel lighter filtering gives.
Grumpy