2. analog
  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
last_lemming OP
639 posts
 
The turntable is two feet away from the other gear. 
I don’t know if this means anything but on the opposite side of the wall the TT is located is the kitchen, and more specifically the oven/range. It’s a gas range but modern so all electronically controlled. Anything could emit from that?

also what I don’t get, is I could have nothing but the table and the cart attached to the arm, no motor, no motor even installed, and I get the hum. 
The Phono unit is dead silent until I connect the tone arm dongle to the VPI “box” the rca’s are in. That what makes me think it’s the cart, I just don’t know what it’s picking up. 
wlutke
744 posts
 
Have you tried floating the grounds on both the amp and line pre at the same time?
totem395
390 posts
 
Time to mount a different another cart for hum comparison.
rms456
49 posts
 
Consider induction from cables in the wall or worst case induction from motors through the platter.
jacahn
28 posts
 
Check the wires connecting the cartridge to the tonearm. Sometimes separating them more/moving them apart slightly can get rid of the hum.  Do this carefully, for example with a toothpick instead of a finger, so you don't break a connection on one of the leads.  Also, check that the phono cables (from the phono to the pre-amp) are not too close to a power cord.
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