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Getting him in my ARC PH3se phono pre

I use two isolation transformer to hook up all my equipment. 
One has the phono pre, TT motor (VPI Prime) and the speed controller equipment for the TT - 250w.  The other has the preamp, and amp - 1000w. 
I’m getting a hum when I turn up the volume when listing to audio through the TT. Here are the are the conditions it’s happening under:

1. Phono pre must be on for hum to occur. If turned off hum goes away. Obviously, so must amp and preamp Be turned at the same time to hear the hum. 2. Phono pre on, but TT motor off, hum is present. So no music playing. Btw motor is controlled by Eagle and Roadrunner. 3. Phono tubes are new and in good condition. 4. The Phono unit is an older unit, but when I had it connected to another system in another room I did not have a hum problem. 
Not sure where to go from here. Especially since I’m connected to isolation transformers. 
last_lemming
twoleftears's avatar
twoleftears
5,313 posts
 
Just google Grado + hum and start sorting through what look like the most useful threads.
last_lemming OP
632 posts
 
 Not sure it’s the cartridge honestly. The hum does not increase or decrease when you move the arm towards the spindle. It hums even with the the arm just sitting In the cradle and the motor isn’t even turned on.  In fact the hum is constant and whether or not you touch the cartridge, or move the wires, or anything like that, it doesn’t change the hum. 
The only thing that has changed it is when I took a power cord and plugged the stereo in from across the house In another outlet.  The hum was greatly reduced. Almost to the point I’m not being an issue at all. That tells me it might have something to do with dirty power or something similar.
But I cannot rule out the cartridge 100%. Because if I just unplug the interconnect cables from the phono preamp I get no hum whatsoever.   It’s only when the interconnects are connected from the turntable to the phono preamp does the hum present itself. 
jacahn
28 posts
 
Check that there are no power cords in close proximity to the interconnects from the turntable to the phono-preamp, and no power cords in close proximity to the interconnects from the phon-preamp to the preamp.
grk
207 posts
 
Try the Granite Audio # 502, which eliminates ground loops.  Quest for Sound is advertising an earlier version (501) on AgoN, but they also can get you the #502.
last_lemming OP
632 posts
 
Ok guys. I’ve been sheltered up for the last day due to Laura - I’m about an hour and a half away Lake Charles. 
I’m very lucky after the last week, puts my problems of humming in perspective for sure. 

I will look into the latest suggestions once I uncover all the equipment and plug everything back in. 
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