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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
Follow Ups:
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?
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.
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
"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!!!!
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?
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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