QSC hum

66.157.95.241

Posted on June 14, 2009 at 08:09:12

chris

The hum comes on when interconnects are connected via the 1/4" jacks, whether something is connected on the other end or not.
It is not the interconnect, as I connected different ones.
What could it be? Does this amp works well with balanced connections? The amp is used in a simple home setup. Thnaks for advice

RE: QSC hum

17:07:43 07/25/09

RE: QSC hum

FenderLover

01:11:46 07/18/09

Ground loop

18:25:15 06/14/09

RE: Ground loop-DON'T DO IT!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ivan Beaver

13:56:41 06/21/09

RE: Ground loop

chris

20:13:09 06/14/09

RE: Ground loop

06:20:46 06/15/09

RE: QSC hum, posted on July 25, 2009 at 17:07:43
Kolby	All of the inputs on the back of the QSC RMX 1450 are balanced, so, you need a positive, a negative and a ground. If you do not have this, you are going to get a hum, what are all of the pieces of equipment that you have leading up to the RMX 1450?

RE: QSC hum, posted on July 18, 2009 at 01:11:46
FenderLover Audiophile Posts: 3309 Joined: July 31, 2007 Contributor Since: May 17, 2009	Are the unused jacks grounded? If not, may want to try grounding plugs (just get a male RCA and solder the center post to the ground tang. See if this helps.

Ground loop, posted on June 14, 2009 at 18:25:15

Pro Sound Guy

You have whats called a ground loop

Easy way out........?
Yes

Get yourself a 25 cent ground lift adaptor from the hardware store
Lift the ground on one of your input units or the power amp

Lift the ground on say your pre amp first...if the hum is not
gone then try the power amp as the last unit to lift the ground
on with the adaptor

Your system will still be grounded

You are just eliminating the ground loop between your pre units
and your power amp

RE: Ground loop-DON'T DO IT!!!!!!!!!!!!!!!!!!!!!!!!!!!, posted on June 21, 2009 at 13:56:41

Ivan Beaver
Manufacturer

Posts: 135
Location: Atlanta GA
Joined: September 1, 2007

"Get yourself a 25 cent ground lift adaptor from the hardware store
Lift the ground on one of your input units or the power amp

Lift the ground on say your pre amp first...if the hum is not
gone then try the power amp as the last unit to lift the ground
on with the adaptor

Your system will still be grounded "

You should NEVER EVER lift the AC grounds!!!!!!!!! The system will NOT be grounded as the shield will not carry enough current should a problem occur.

He needs to find the REAL problem-NOT a dangerous band aid.

I suggest hooking up the balanced input to the amp as balanced and not hooking up the shiled wire.

On the preamp end hook the hot wire from the amp to the hot output of the preamp. Hook the cold wire and the shield to the ground of the preamp.

That will fix it most of the time-and he can take advantage of the commmon mode rejection of the amp balanced input.

There is not a Judge in this land who wants to hear how "the hum went away" when somebody has used a widowmaker ground lift to get rid of the noise!!!!

RE: Ground loop, posted on June 14, 2009 at 20:13:09

chris

Thank you! But the hum (buzzing sound)comes when the interconnects are not even plugged-in the pre-amp. I thought 1st that the interconnects were faulty, so I changed them. I use interconnects that are terminated with RCAs and a RCA to 1/4 jack adaptor to fit the rmx 1450 inputs. In addition the amp is picking up other electrical devices; with the microwave on for instance, the amp starts to generate a 60 to 100 hz hum.
When I un-plug the interconnects from the amp, the speakers become dead silent. Could it be the jack? or is the amp not well designed for unbalanced inputs?

RE: Ground loop, posted on June 15, 2009 at 06:20:46
Pro Sound Guy	Sounds like you have a bad interconnnect Unplug one at a time If it goes dead silent after you unplug one then you found it Otherwise try a different circuit Possible neutral/hot reverse on AC outlet?

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QSC hum

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