Noisy regulated supply

[gls]

I have a wallwart, "Newstar" brand, 3-12V (700mA at 12V) "IC" regulated. Feels a little light. It's incredibly noisy - any ideas why? Zapped me once when I tried to run a mini-amp from it too. =(

[niftydog]

describe the noise... hum, hiss?

Chances are it's a switch mode if it's light and noisey!

[Samuel]

i believe that noisy and regulated are not mutually exclusive terms...it could well be regulated, i.e. puts out a constant voltage regardless of load, and still have crappy filtering...

[brett]

If its switchmode, you'll need a filter.  Try this;

It'll also cut noise from flouro lights, etc.  A couple of my friends who play at various venues are enthusiastic about it.
cheers

[gls]

Its like hum/buzz, yeah...but so loud that you can't hear the guitar over it!I'll try that filter, thanks.

[R.G.]

STOPSTOPSTOPSTOPSTOPSTOPSTOP!

You said:

Zapped me once when I tried to run a mini-amp from it too...
Its like hum/buzz, yeah...but so loud that you can't hear the guitar over it

It's leaking AC power line voltage to the output. Here's what to do to fix it:

(1) take it out to your garage
(2) place it on the concrete floor
(3) using a hammer, pound it into dust
(4) place dust in trash can
(5) get a different adapter that does not put your life at risk.

The loud hum/buzz is the leakage.

[Paul Perry (Frostwave)]

I think RG is right! (As usual!)
Some switchmode supplies are intended to be used with insulated plastic body devices & do not fully isolate from the mains.
So maybe that is what you have here!!
personally, I would't mess about with something I got a shock from. :shock:  :x

[niftydog]

Its like hum/buzz, yeah...but so loud that you can't hear the guitar over it!

um, yeah... well I was going to say it might be worth measuring the AC on the supply line to see if it's ripple... had you measured it at all before plugging it into stuff?!?

Given the price of wall warts these days, I'd take RGs advice!

[gls]

i'm still alive! thanks. the outlet in question does weird things like cut off when I turn something on. electrician said it was fine. maybe it's time for a new one (outlet and electrician).