2. tech-talk
  3. 128479-46

Can't tell,if my house is properly grounded

Hey guys, I have a low level hi/low buzz that is coming through my speakers, not dependent on the integrated tube amps volume. It is amplified when I turn on my Parasound JC3+ Phono preamp, but only slightly. I have the power cords going to the same outlet. I tried running their power through my Furman Elite Power conditioner but that changed nothing. I ran an independent ground wire and checked all the components in various configurations to no avail. I disconnected all the tv cable to make sure it wasn't coming from there and that solved nothing either. I turned off everything in the house I could' no change. I checked my ground outside at the rod and it is all solidly connected, however the depth of the rod is unknown.

any other thoughts before I call out an electrician?
last_lemming
oscar44
130 posts
 
Am a bit confused about what has changed. Seems like hum came when you changed room...and the gear change was a switch to single ended rather than balanced cables from phono stage, and new speakers? Speakers and amp seem to check out ok, correct? But the phono cable introduces the noise? Can you go back to balanced cables to see if that matters? If not, can you adjust the gain level on the phono to see if that has any effect?
last_lemming OP
638 posts
 
Ok, I did everything everybody said, and there is no change buzz is still there.

to answer a question from above I switched the room the phono pre was in and went from single ended to xlr because the tube amp doesn’t have xlr. I have had the same issue with an old Conrad Johnson amp, where it would buzz as well.

Could the tube amp be the culprit? Bad tube?

i also noted that the buzz/hum is older on different wall outlets. 
last_lemming OP
638 posts
 
I second Erik's suggestion of having a tech look at it. There is the possibility that a safety cap in the receptacle is leaking ac, especially the one from N to ground. If the fuse blew with that extension cord, it's possible you reversed polarity and ac went to ground through the bad cap, especially if there is an earth line choke between the safety caps.

To be clear it made the noise prior to me trying to use the cheater plug that flipped the polarity. 
jea48
4,422 posts
 
One more test.

With only the preamp connected to the power amp, TT not connected to the inputs of the preamp, unplug the preamp from the AC power.  Turn on power amp and check for the buzz/hum.




last_lemming OP
638 posts
 
With only the preamp connected to the power amp, TT not connected to the inputs of the preamp, unplug the preamp from the AC power. Turn on power amp and check for the buzz/hum
Did this and no hum.  I'm not clear what that proves or disproves, if the preamp isn't plugged in then the ground isn't plugged in and no ground loop can occure. 
More to discover