So what's the deal with the power supply?

[JimRayden]

I've read many of you trying to isolate the power supply jack from the chassis. Is there a certain reason for having a "-" in the center of the power jack and the 9 volts on the outside?


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Jimbo

[R.G.]

It's a little like Ben Franklin assigning polarities to electricity, or why we use QWERTY keyboards. The first guy there got it wrong, but it became so entrenched that we can't get rid of it.

Boss did the first power adapters and plugs. For reasons unknown, they put the - on the center pin, + on the shell, and proceeded to sell zillions of the only effects that took a power supply. So folks built power supplies that did that, and then other people built effects that worked with Boss and 3rd part power supplies, ... and so on down the broad, well lit road to hell.

I don't know if it was malicious, but that's how it started.

[JimRayden]

Thanks. I think I'll join the cult.


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Jimbo

[NaBo]

What R.G. said.

If you have metal DC jacks, and are making your own power supply or dc cables, then by all means, save yourself the trouble and make it centre positive.

Otherwise, might as well play it safe and conform to the machine.  :wink:

[The Tone God]

Barrel type adapters are far more robust and common then pin adaptors. This is why just about anything with an adpator comes with a barrel connection. Mechanically it is far easier to switch the outer ring in the jack then the center pin. Typically when designing a power supply with a switching source you would want to switch the posistive line and not the ground so you can deal with conditioning the input power. So there you have the outer ring, which is easy to switch in and out, becoming posistive, which is what you usually want to switch in a power supply.

In the schem of things this affects very few manufacturers since they typically do not connect the jack physically to the case or if they do it is not to a case that is metal and they want to ground. It does however affect us but we are so insignificant in the world of consumer electronics that they are not going to make the change just for us.

If its a real problem for you just build an adaptor to flip the power from the supply before it hit your pedal.

Andrew