2. misc-audio
  3. 1037297108

Slight hum from left speaker -- Help appreciated

Two weeks ago I installed a new amp and preamp (Pass Aleph 30/FT Audio LW-1) in my system and since then I've had a very slight hum from my left speaker. It's not distracting, but it's something I'd like to get rid of. I've switched out interconnects and speaker cables and nothing changed. I did a search for ground loop hums and I could not find any useful information other than cable TV may be a problem and we don't have cable. Any hints on what could be causing the hum would be greatly appreciated. Thanks!
budrew
budrew OP
467 posts
 
Uh, excuse my ignorance, but how does one "float the ground"? (Thanks for the useful tips!)
newbee
4,811 posts
 
Your plug has three prongs, the positive, the negative, both of which are flat, and the ground which is round. You will in essence be disconnecting the round ground prong. To do this go to you hardware store and get a "cheater plug" this is a plug which has three slots for your plug but only has the two flat prongs - these you plug into your outlet. Do not connect the ground wire on the cheater plug to anything.
budrew OP
467 posts
 
I tried it all. I floated the ground, exchanged the right and left speaker wires (the hum moved to the right speaker), changed right and left amp-preamp interconnects (no change), and moved wires and interconnects around. Nothing solved the problem. My preamp is passive so I'm only turning the amp on for this testing. The only thing that was proven was that the left speaker wire seems to tbe the trouble. Whichever speaker it was connected to was humming. Is this an amp problem? I am using the RCA inputs. The amp also contains balanced inputs and there are "short jumpers" between pin 1 and 3 on each channel. I checked them, but they seem firmly placed. The hum is very slight. Thanks!
bomarc
501 posts
 
I'm assuming that when you say you "changed right and left amp-preamp interconnects (no change)," you mean you changed them only at the amp end, and that the hum stayed on the left. If so, then you've got the problem narrowed down to two suspects: the amp and the left speaker cable. To eliminate the cable as a suspect, switch the cables at both the speaker and amp ends. If the hum is still on the left, then the problem is the amp. If it moves to the right, then you've got a bad cable.
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