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  3. 159523-46

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
br3098
971 posts
 
This sounds like a ground potential issue. Try running a ground strap from the phono pre to your preamp. I know you tried what millercarbon suggested but sometimes you need to isolate two plugs in the same receptacle. I have had good luck using a simple surge protector like these: Tripp Lite ISOBAR6Ultra Power Strip
wlutke
717 posts
 
I had the same hum with my 2 prong cord on an ARC sp-9 and a 3 prong amp.  I used a cheater plug with the ground removed for the amp.  Not smart or safe but effective.

last_lemming OP
632 posts
 
I have done the ground wires to no avail. In fact I have run a ground wire from all the components and tried all kinds of combos. Nothing changes the hum.

i have a Hum X cheater plug and that did nothing either. 
mijostyn's avatar
mijostyn
8,227 posts
 
Last_Lemming, the Grado hum will get louder as the cartridge gets closer to the motor. I would start floating grounds starting with the Phono preamp.
mijostyn's avatar
mijostyn
8,227 posts
 
woops, I see you have used the cheater plug. Remove the positive signal wires from the cartridge.
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