M4 grounding question

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Bucksears

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I just got my RT2/50 out of the shop after suspecting that the low-pitch hum I was getting from it was from it and not my M4. The hum increased when I turned up the RT2/50, did not change when I turned up the M4.
The tech said the Randall was fine and suggested that I look at whatever preamp I was plugging into it. I knew that I had the M4 ground switch set to NORMAL; he suggested lifting that to see if it affects the hum.

It did. I switched it over to LIFT and the hum went away.

The only thing that I'm concerned about is that the M4 manual/doc reads that it should be set to NORMAL unless it's in a grounded rack; but it does say to set to the least noisy position. I finally got my setup to where I want it, with the hum gone and lower-noise fans now in the M4 and RT2/50. (just waiting on that EG5 now)

Since I just have my M4 setting on top of my RT2/50 and that's it (no case or rack), is that safe??
I'm getting more and more attached to this setup, but don't want a fatal shock from it. :D
 
No worry about getting a shock. The M4 is known for this hum when paired with an RT2/50. Had the same hum with mine. If it's quiet, you are good to go.
 
To beat a dead horse . . . I just threw my spare M4 on top of my secondary rack yesterday, and noticed the same thing; I flipped the GROUND LIFT switch and the hum went away. But I never even look to see what position the GROUND LIFT switch is set to, I just set it to whichever is the quietest - that's where you should set it, with no worries either way . . . :thumbsup:
 
Before I got my RT50 I was using a VHT/Fryette 2/50/2 with my M4.
The VHT also required the M4 ground lift switch to be on to avoid hum.
 
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