Sans Battery

[Phend]

So is a wallwort considered a subpar power supply?
I've seen numerous post here advising to try "using a battery" to see if the "problem" goes away.
Is there a power supply available such as amptramp's design? 

[GibsonGM]

Way I see it, is sometimes people grab a wall wart meant for a phone, or other gadget, that is designed just to provide 'whatever' voltage for something to run on...and maybe the device has internal filtering. So we use it on an audio circuit, and all that ripple and noise crap comes thru.

So we suggest a battery because it is guaranteed to provide a clean 9V DC with no ripple, thus indicating a problem w/the wall wart..and also, if the power jack isn't wired right, the battery may show this...

[ElectricDruid]

+1 what Gibson said.

Not all wallwarts are subpar, but there's certainly a huge number of cheapo-rubbish wallwarts in the world, so if you grab one at random, the odds aren't good.

A battery is a good test as a way of eliminating various possible problems stemming from the power supply. If all that hum or high-pitching whining magically goes away...well, there's your answer, and there's nothing wrong with your circuit. If it still does it, even running off a battery, you've definitely got something that you need to fix.

[GibsonGM]

Or if it does the same thing on both supplies, maybe you are testing the circuit too close to your computer, LOL....ask me how I know...