Monitor Hum!!!

[pinklesson]

Hello Slutz!!!

Can anyone be kind enough to enlighten me as to why this is happening????

So I sit in my room where there is only one power outlet. The only thing I plug into it is my powered monitor (Event ALP5) with no signal cable connected or anything. Just the power cable. No other things in the room are running.

There is an annoying hum in my speaker and when I moved the power cable around in different positions the hum decreases in certain spots. Almost disappears sometimes...

Any ideas what's going on?

Thanks.


I love Slutz!!!!

[EveAnna Manley]

Does it hum also with something connected to the input? It is not unusual for something to hum or buzz with an open input. Go ahead and find the quietest place for that power cord while you're at it though.

[pinklesson]

Yeh it does still hum when something's connected...
Also the the amount of gain on the speaker has no effect on the hum. It's exactly the same whether it's cranked right up or turned right down...

[tINY]

Powered monitors....

Are there florecent lights or motors (AC, pumps, heater blowers, conveyor belts) nearby?



-tINY

[Matt Syson]

Hi
I presume that your mains settings are correct and that your mains supply is not too high, as this could cause the transformer to start to saturate. Is the hum mechanical (the box vibration) or 'audible through the speaker cone'?
Is your mains quite 'clean' and non distorted. If you have a supplty conditioner available does it make any difference?
Matt S

[pinklesson]

Thanks for the replies.

I'm in Australia by the way... so my outlet is constantly delivering 246-248V. So that all seems fine.

The hum is audible through the speaker cone. There is a buzz along with the hum also. Putting my finger on the cone eliminates some of the hum. Sometimes just grabbing the cable eliminates the hum.
I can also hear some radio through the speaker.

Trying to vomit out as much info here....

No conditioner to try out.
There's obviously some kind of interference, but I'm dying to know why it is happening. And why it disappears when I just lift the cable slightly...



Should I be looking at getting a shielded IEC power cord?

[Radioman]

Originally Posted by pinklesson

I can also hear some radio through the speaker.

Should I be looking at getting a shielded IEC power cord?

Maybe RF interference from a local broadcaster intermodulating with AC mains.
A shielded IEC power cord could help you.
Try putting a EMI filter on the AC mains cords and/or wounding mains and audio cable into a ferrite ring.
You can add a ferrite bead on AC and audio cables too.

[Matt Syson]

Hi
Physically moving cables around can reduce or even eliminate hum and or interference as you can often 'cancel' it out by having the 'interferance' out of phase. The root cause should be sought really because you don't want to have to tinker with wiring position every time you change ANYTHING!
The fact you have some radio in there is a clue as this should not be happening at anything like a level that interferes with line level monitor signals. Find out which station is broadcast and get technical details from them. A 100KW transmitter 500 Metres down the road will upset things.
Ferrite beads, rings, filters, foil on walls, metal plate the room, pull the nearby transmitter down, move house (studio), the list starts off cheap!
Actually, contact the monitor manufacturers as they should not be so sensitive to 'airborne' interference.
Good luck
Matt S