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Ground Wire

The tonearm cable is plugged into RCA input of the phono stage. The tonearm ground wire is connected to the ground post of the same phono stage. The first RCA L/R outputs of the phono stage are connected to a pair of mono blocks. There is no hum I could hear coming from the speakers connected to them. The second L/R outputs of phono stage are connected to the line input of the integrated amplifier that drives a second pair of speakers. That's where the hum is quite audible. That integrated amplifier also has the ground post. I wonder if I could get rid of the hum by connecting the phonostage's ground post with the ground post of the integrated amplifier. What kind of wire should be used to connect two ground posts of two different preamplifiers? The units are at least 8 feet apart. 
esputnix
fiesta75
1,378 posts
 
You've definitely created a ground loop. Everything should be to one outlet on the same line. Avoid different power lines at all cost. Ground problems are TRICKY. You might want to look into a ground block. 
itsjustme
681 posts
 
Very likely a ground loop complex topic why don’t you Google and read up on ground loops and then do a bunch of experiments to identify it and eliminate it also how are you driving mono block amplifiers with a phono stage and no volume control in between them seems to me you’re leaving something out of this
bpoletti
1,552 posts
 
Try it. What's the worst that could happen?
speakermaster
738 posts
 
the hum is caused by using components on two different ground potentials you need to use all of the amps on the same outlet or you will have these sorts of problems.
pedroeb
493 posts
 
Perhaps the most important consideration is not to create a grounding loop. In that regard every piece of equipment should be connected to a central point.

Sometimes it can be excessive hard when using RCA as the shield serves two purposes: the second side of the signal and a grounding path. With balanced or XLR one end of the shield can be disconnected if absolutely necessary when a groundling loop is created.
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