|
|
Post by gus4emo on May 9, 2020 14:43:37 GMT -5
Hi all, so I got a 2nd unit, have an A150 and an XPA200 plugged in one, and another A150 and an XPA7 plugged into the other one, but the only amp still humming is the XPA7, what takes, by the way I separated the interconnects from the cords....the louder channel in the XPA7 is the surround back channel, and another thing, one CMX2 has 2 blue lights on, the other has one light on....  ?? they are both plugged in the same outlet...I had fixed the humming years ago, but it came back after adding 2 A150s, but like I mentioned, the only one humming is the XPA7.... |
|
|
|
Post by Boomzilla on May 9, 2020 18:26:20 GMT -5
I don’ recall the meaning of the CMX lights - does anyone else?
As to the amp humming, I’d think that if it were a power-strip issue, BOTH amps should hum.
OTOH, if one of your amps had a shielded power cord and the other not...
Or if one of your amps was hooked up with balanced XLR interconnects and the other with unbalanced RCAs...
But neither of those circumstances would account for but one channel humming on a multi-channel amp.
|
|
|
|
Post by gus4emo on May 9, 2020 20:10:39 GMT -5
I don’ recall the meaning of the CMX lights - does anyone else? As to the amp humming, I’d think that if it were a power-strip issue, BOTH amps should hum. OTOH, if one of your amps had a shielded power cord and the other not... Or if one of your amps was hooked up with balanced XLR interconnects and the other with unbalanced RCAs... But neither of those circumstances would account for but one channel humming on a multi-channel amp. Thanks for the reply, I guess I have to figure it out, the surround back channel, the right channel is the loudest, but I have to put my ear a few inches from it, about a foot from it not bad, just when I get my ear on the grill I noticed its loud, the rest of the channels not even close.... |
|
|
|
Post by Boomzilla on May 9, 2020 20:24:38 GMT -5
Switch the two CMXs. If the noise stays in the same channel, it’s the amp.
|
|
|
|
Post by gus4emo on May 10, 2020 9:36:24 GMT -5
Switch the two CMXs. If the noise stays in the same channel, it’s the amp. I did just that, still the same, and it's weird, a couple of weeks ago it wasn't there, let me ask you, should I get a 3rd CMX2, to plug the receiver on it? I have $30 off from Emotiva, or should I just leave it alone, save the money... |
|
|
|
Post by donh50 on May 10, 2020 10:20:46 GMT -5
If you added an amp, and it created a new ground loop, then a power strip (DC blocking type or not) is unlikely to cure it. You may need to reroute power connections, add a low-impedance (big wire) ground path, or use a ground isolator on the signal connections.
It is also possible you have a bad interconnect cable; could try swapping them around. Make sure everything is off first!
|
|
|
|
Post by gus4emo on May 10, 2020 14:09:23 GMT -5
If you added an amp, and it created a new ground loop, then a power strip (DC blocking type or not) is unlikely to cure it. You may need to reroute power connections, add a low-impedance (big wire) ground path, or use a ground isolator on the signal connections. It is also possible you have a bad interconnect cable; could try swapping them around. Make sure everything is off first! The one channel that is the loudest is the one giving me headaches, the sound is good, just the hum...I disconnected the cable and it's dead silent, plugged it back in and the hum is there again, all cables are Mediabridge, shielded, being great, can it be the receiver, it's plugged into a CMX6, which is not a filter like the CMX2... |
|
|
|
Post by donh50 on May 10, 2020 14:20:51 GMT -5
The power strips will not usually change a ground loop, except to perhaps make it worse. Are all of your interconnects RCA?
You said it was not there a couple of weeks ago; is that after you added the new amps? If so, and adding the amps did not matter, that channel of the XPA7 may be going bad.
If you unplug the other amps from the power socket/strip, leaving the interconnects attached, does the hum go away?
Again, always power everything off and wait a few seconds before making any changes.
|
|
|
|
Post by gus4emo on May 10, 2020 19:57:16 GMT -5
The power strips will not usually change a ground loop, except to perhaps make it worse. Are all of your interconnects RCA? You said it was not there a couple of weeks ago; is that after you added the new amps? If so, and adding the amps did not matter, that channel of the XPA7 may be going bad. If you unplug the other amps from the power socket/strip, leaving the interconnects attached, does the hum go away? Again, always power everything off and wait a few seconds before making any changes. I got rid of a power strip that was plugged into another strip, and the power strip plugged into the CMX6, I plugged it into the wall, the hum in the surround back right diminished a bit, the hum in the surround back left is almost gone, my take is it might just be bad current causing the crap, what do you think? |
|
|
|
Post by donh50 on May 10, 2020 20:29:17 GMT -5
"Bad current", no; ground loop, probably. Plug everything into the same outlet on a single strip if possible.
|
|
|
|
Post by gus4emo on May 11, 2020 9:00:50 GMT -5
"Bad current", no; ground loop, probably. Plug everything into the same outlet on a single strip if possible. I will keep at it.... |
|
cawgijoe
Emo VIPs 
"When you come to a fork in the road, take it." - Yogi Berra
Posts: 5,033
|
Post by cawgijoe on May 11, 2020 9:15:03 GMT -5
"Bad current", no; ground loop, probably. Plug everything into the same outlet on a single strip if possible. I will keep at it.... Ground loops are a real pain.... |
|
|
|
Post by DavidR on May 11, 2020 9:49:53 GMT -5
The one with only one light may have an LED that no longer works. I have one where this happens but it is the one where I had an object fall on to the unit and that's when it stopped working. There is a legend for the light sequence on the CMX that will let you know if your receptacle wiring is correct.
I second the idea to swap CMX units.
|
|
|
|
Post by gus4emo on May 11, 2020 13:07:50 GMT -5
The one with only one light may have an LED that no longer works. I have one where this happens but it is the one where I had an object fall on to the unit and that's when it stopped working. There is a legend for the light sequence on the CMX that will let you know if your receptacle wiring is correct. I second the idea to swap CMX units. I did swap, still the same, how about an isolator for the one channel? I got rid of one strip, plugged the other one straight to the wall, hum diminished a bit on the loudest (surround back right), the hum on the surround back left channel is almost gone...disconnected the cable from that (surround back right) channel and it was dead silent, reconnecting it back the hum came back...can it be the preamp from the receiver, the cable is great, Mediabridge, shielded.... |
|
|
|
Post by gus4emo on May 11, 2020 20:46:36 GMT -5
"Bad current", no; ground loop, probably. Plug everything into the same outlet on a single strip if possible. I could pick up a ground loop isolator... |
|
|
|
Post by rbk123 on May 12, 2020 7:39:23 GMT -5
Have you tried plugging a different source into that channel -i.e. front right, or swapping the surrounds? Also, have you swapped the speaker outs on that channel to another of your speakers?
|
|
|
|
Post by gus4emo on May 12, 2020 11:10:36 GMT -5
Have you tried plugging a different source into that channel -i.e. front right, or swapping the surrounds? Also, have you swapped the speaker outs on that channel to another of your speakers? Will try that, I unplugged the rca from the one channel on the amp, dead silent, plugged it back in, hum is back. |
|
|
|
Post by DavidR on May 12, 2020 13:24:11 GMT -5
Check that rca cable. I once had one where the solder was a big blob and it was so big it was grounding
|
|
|
|
Post by gus4emo on May 12, 2020 13:35:44 GMT -5
Check that rca cable. I once had one where the solder was a big blob and it was so big it was grounding Will do, although besides the hum, the sound is as good as always, but will check... |
|
|
|
Post by rbk123 on May 12, 2020 13:36:47 GMT -5
Will try that, I unplugged the rca from the one channel on the amp, dead silent, plugged it back in, hum is back. Could be the interconnect, or that channel on the XMC, or that channel on the amp, or the speaker/speaker wires. Use a different interconnect with a different channel out on the XMC and see. If you use a different interconnect, from a channel with no hum so you know the cable is good, with the same XMC and XPA channels and the hum is still there, it's the amp channel (or the speaker/speaker wire). Lastly try the same channel combination with an XLR and check for hum; try different channel combinations with XLR as well like above. Could just be the un-balanced circuitry of that channel. If you get the hum via XLR, it's the channel (or the speaker/speaker wire). For speakers, if you swap around the speaker leads and the hum stays in the same speaker, it's the speaker or the speaker wires. If it follows to the new speakers it's the amp channel.[/quote] |
|
?? they are both plugged in the same outlet...I had fixed the humming years ago, but it came back after adding 2 A150s, but like I mentioned, the only one humming is the XPA7....
