Rocktron DC On Tap wall wart system - noisy?

[Steve Conner]

Hi all,

The other day I bought the Rocktron DC On Tap 9v wall wart and cable set to power my stomp boxes. To my disgust I found that the switched-mode power supply adds a loud hiss/screech to my audio.

I knew that the wall wart was switched mode, but I was prepared to give it a try anyway. I'm going to see if the store will exchange it for a different model, but I wonder if anyone else has had trouble with these?

[Mark Buckingham]

I actually had troubles not with the Rocktron but with "the spot." It actually works great on all of my pedals except for my old butler Tube Driver.

I'm not sure why, but the tube driver can't be connected to the same dc supply as my delay, chorus, etc... It's ok connected to the spot alone, or if I give it its own power. I'm pretty sure the Spot thingy is a switcher also.

[Enzo]

A friend had a Scully recording amp, and wanted to make it into a mic pre. I stuck a switcher in that and it was clean. I'd be thinking defect rather than technology type.

[Mark Buckingham]

I'm not really knocking the technology... I just think there is something funny about the combination of the tube driver & the power supply. My guess is that it could be due to the heater for the tube being powered by the 9vdc coming in.

[Enzo]

Steve seemed to imply that it was a switcher, hence the noises he was getting. I could be wrong.

[Steve Conner]

Hi Enzo, yes it was a switcher, and I believe the noise was switching noise. The shop exchanged it for one of those big metal cased "Power Bank" thingies, so should be no more worries.

I agree that switchers don't necessarily have to be noisy. My mixer has a switcher in it for everything, including phantom power But the switcher in the Rocktron package seems to be a very cheap and nasty one! It looks similar to the $15 Chinese wall warts we used to buy in bulk at the place I used to work. Some of these don't even have a proper controller chip: they're just a ghetto self-oscillating circuit. They were pretty noisy, but we just added a filter to our product.

Mark: If the problem brings the power down, it's more than likely that you are mixing negative ground stompboxes with positive ground ones. You need to find the positive ground ones and dedicate a separate isolated supply to them.