Tech: Noisy Power Adapter/Wall Wart ?

Subject: Tech: Noisy Power Adapter/Wall Wart ?
From: GUEST,Arthur Stiffy
Date: 22 Sep 09 - 12:52 PM

I've just aquired a brand new Danelectro DA-1 guitar pedal power supply
included with a bargain bundle of the newish well reviewed "Cool Cat" pedals.
Its marketed as a Regulated 'Zero Hum Circuit' 9V AC Adapter
and is the correct model for The UK.

Plugged in and using it for the first time first time and everything works fine,
except for a very noticeable constant trebly kind of hum
I've located as being emitted from within the plastic casing of the power adapter.

No unwanted hum from the the amp & speakers [guess the 'zero hum circuit' must be working then ].
But the black plastic adapter unit is itself an irritating source of noise at home practice volume level.

I've never before noticed this 'problem' with any other adapters
from various music and misc electronic product brands.
So is this a malfunctioning unit,
or a side effect of the 'zero hum circuit' ?

Subject: RE: Tech: Noisy Power Adapter/Wall Wart ?
From: John J
Date: 22 Sep 09 - 03:11 PM

Assuming it's a linear power supply then it's most likely that the laminations on the mains transformer are vibrating - this shouldn't happen. A linear power supply has a standard mains transformer.

If it's a switch-mode power supply (lots of electronics in the box, small high frequency transformer) then it's a different matter.

Does the hum / buzz stop when it's unplugged from the pedal? If so then it could be that the power supply is trying to work too hard.

What is the current output of the power supply - and what is the current requirement of the pedal?

Where are you located?

John

Subject: RE: Tech: Noisy Power Adapter/Wall Wart ?
From: Barry Finn
Date: 22 Sep 09 - 03:46 PM

What do you expet when shopping at Wal-Mart. They're very good at refunding but their merchandise is shit. You get what you pay for

Barry

Subject: RE: Tech: Noisy Power Adapter/Wall Wart ?
From: EBarnacle
Date: 22 Sep 09 - 11:05 PM

That's wall wart, not Wal-Mart, Barry

Subject: RE: Tech: Noisy Power Adapter/Wall Wart ?
From: Barry Finn
Date: 23 Sep 09 - 01:40 AM

Thanks Eric, I see my wiring got crossed again.

Barry

Subject: RE: Tech: Noisy Power Adapter/Wall Wart ?
From: GUEST,leeneia
Date: 23 Sep 09 - 12:16 PM

Here are a couple thoughts - they may no apply to you, Arthur, but they may help someone else someday.
========
I have a friend who wires new houses for stereos, intercoms, alarms, etc. He has to make sure that no two lines carrying current cross one another, especially at a right angle. Why? because the magnetic field around one will set up a current in the other, creating some form of unwanted sound.

I used to get a hum in my stereo (living-room) when the rheostat on the dining room light was dialed. Turned out that, down in the basement, the wire to the rheostat crossed the wire going to the speaker in the kitchen.

So, Arthur, make sure no wires in your setup are crossing each other. Any kind of wire - sound, electrical, doorbell...

Another thing - don't pile excess wire into coils. I don't know why this is bad, but I have heard that we shouldn't do it.