Ground loop problem, or more?

[Tungsten06GT]

Hey guys,

Let me quickly try to describe my problem without confusing anyone. I've owned the eD a7s-650 for almost a year now with the lt1300 amplifier. A little more than a month ago, at the end of the night when I shut everything down, there was an faint audible hum coming from the amp. I thought it was a fluke, but then it happened again a couple weeks ago. And finally it's been happening about every other night for a week now. I have the amp set for "auto off", and when it does shut off, the next time I turn it on the hum is gone. I can also manually turn the rocker switch off, but turning it right back on does nothing, I need to keep it off for a while (seems like voltage somewhere isn't dissipating). What's weird is that the hum is not there to begin with, but after watching tv, not even pushing the amp, I'll just realize there is a hum.

The amp already has a 2 prong plug only, and when the hum is there and I pull the rca cable out, the hum remains. Adjusting the gain does nothing. It's localized to the amplifier, and whatever it is, doesn't get amplified. I tried moving the power cord to a different outlet and the hum will still come about. When the hum is there and I'm watching something, the subs still play fine with no issues (the hum i annoying enough though, it shouldn't be there).

What's difficult is that the problem is random, but it has been happening more frequently. Could there be a ground loop being introduced by any of my other equipment that's on the same breaker? But if so, why has the problem just now come about and it seems to be getting worse? eD had me try to move the plug to a different outlet, but that didn't fix anything.

Thanks in advance and sorry for the long read!

 

[TLS Guy]

Hey guys,

Let me quickly try to describe my problem without confusing anyone. I've owned the eD a7s-650 for almost a year now with the lt1300 amplifier. A little more than a month ago, at the end of the night when I shut everything down, there was an faint audible hum coming from the amp. I thought it was a fluke, but then it happened again a couple weeks ago. And finally it's been happening about every other night for a week now. I have the amp set for "auto off", and when it does shut off, the next time I turn it on the hum is gone. I can also manually turn the rocker switch off, but turning it right back on does nothing, I need to keep it off for a while (seems like voltage somewhere isn't dissipating). What's weird is that the hum is not there to begin with, but after watching tv, not even pushing the amp, I'll just realize there is a hum.

The amp already has a 2 prong plug only, and when the hum is there and I pull the rca cable out, the hum remains. Adjusting the gain does nothing. It's localized to the amplifier, and whatever it is, doesn't get amplified. I tried moving the power cord to a different outlet and the hum will still come about. When the hum is there and I'm watching something, the subs still play fine with no issues (the hum i annoying enough though, it shouldn't be there).

What's difficult is that the problem is random, but it has been happening more frequently. Could there be a ground loop being introduced by any of my other equipment that's on the same breaker? But if so, why has the problem just now come about and it seems to be getting worse? eD had me try to move the plug to a different outlet, but that didn't fix anything.

Thanks in advance and sorry for the long read!

It is not a ground loop.

I assume the hum must go away after a sort period of time after you pull the plate amp power cord.

The plate amp has a failing power supply and is dangerous. The plate amp needs replacing.

 

[j_garcia]

Agreed. It sounds like it may be having trouble dumping the charge from the capacitors sometimes when it is powered off. Regardless of what the issue actually is, I would have it looked at.

 

[highfigh]

Hey guys,

Let me quickly try to describe my problem without confusing anyone. I've owned the eD a7s-650 for almost a year now with the lt1300 amplifier. A little more than a month ago, at the end of the night when I shut everything down, there was an faint audible hum coming from the amp. I thought it was a fluke, but then it happened again a couple weeks ago. And finally it's been happening about every other night for a week now. I have the amp set for "auto off", and when it does shut off, the next time I turn it on the hum is gone. I can also manually turn the rocker switch off, but turning it right back on does nothing, I need to keep it off for a while (seems like voltage somewhere isn't dissipating). What's weird is that the hum is not there to begin with, but after watching tv, not even pushing the amp, I'll just realize there is a hum.

The amp already has a 2 prong plug only, and when the hum is there and I pull the rca cable out, the hum remains. Adjusting the gain does nothing. It's localized to the amplifier, and whatever it is, doesn't get amplified. I tried moving the power cord to a different outlet and the hum will still come about. When the hum is there and I'm watching something, the subs still play fine with no issues (the hum i annoying enough though, it shouldn't be there).

What's difficult is that the problem is random, but it has been happening more frequently. Could there be a ground loop being introduced by any of my other equipment that's on the same breaker? But if so, why has the problem just now come about and it seems to be getting worse? eD had me try to move the plug to a different outlet, but that didn't fix anything.

Thanks in advance and sorry for the long read!

The hum was coming directly from the amp, or through the speakers connected to that amp? If it was coming from the amp itself, it's just the transformer and if it's coming from the speaker(s), it could be that the preamp/receiver shunts the output- amplifiers usually exhibit the worst S/N ratio at that time. Shut the amp off, unplug the cable, turn it on and listen for hum- if it goes away, it may not have any problem, at all.

 

[highfigh]

Agreed. It sounds like it may be having trouble dumping the charge from the capacitors sometimes when it is powered off. Regardless of what the issue actually is, I would have it looked at.

Caps don't dump AC.

 

[Tungsten06GT]

The hum was coming directly from the amp, or through the speakers connected to that amp? If it was coming from the amp itself, it's just the transformer and if it's coming from the speaker(s), it could be that the preamp/receiver shunts the output- amplifiers usually exhibit the worst S/N ratio at that time. Shut the amp off, unplug the cable, turn it on and listen for hum- if it goes away, it may not have any problem, at all.

The hum is coming directly from the amp. When I yank the RCA cable out after I turn the receiver off, the hum is still there. It never made this hum for the first 8 months I owned it, now it's happening more frequently and only after the amp is on for a bit. Tech support at eD said it could be from resistance issues with an internal fuse on the power board, however the person I was talking to said it's only happened a handful of times while they've been working there.