Author Topic: Why is the DC plug centre negative? Is it acceptable to do it the other way?  (Read 804 times)

mjg

  • Electron Doctor
  • *****
  • Posts: 855
  • Matt
    • View Profile
    • My pedal blog
Hi,

I've done a few electronics projects over the years, but just getting into pedal making. 
In every other electronics area that I've worked in, convention seemed to be that the DC power plug/socket is centre(tip) positive, with outside negative. 

*After* building about 6 pedals for my kid, I realised that pedals seem to be wired with DC centre negative.  For compatibility with popular pedals of the past? 

So... should I rewire all the DC plugs on the pedals that I've done so far?  Will my kid turn up with his pedals and find he can't plug them in to anyone else power supplies?  Or is it acceptable to have either way?  :-\

Just wondering if it is better in the long run to rewire the pedals I've done already.  (And also rewire the power supply too!)

Ta,
Matt.

m-Kresol

  • Electron Doctor
  • *****
  • Posts: 2733
  • Felix - Graz, Austria
    • View Profile
    • My blog - in german
I think it was Boss that started the whole centre negative thing and almost all pedals are built this way by now. There are a few exceptions, like old BBD delays, but most are 9V DC centre negative.

There's no reason to not do it the other way. As long as you and your son are aware of the fact that most power supplies that come with commercial pedals won't work or even damage your diy builds and vice versa, everything should be fine. Nevertheless, if you find the time to rewire them, I would do it just for the sake of uniformity
I build pedals to hide my lousy playing.

My projects are labeled Quantum Effects. My shared OSH park projects: https://oshpark.com/profiles/m-Kresol
My build docs
My etching tutorial

midwayfair

  • Electron Doctor
  • *****
  • Posts: 7091
  • Jon P
    • View Profile
    • Midway Fair
It has to do with how the power is switched when you are using a battery OR power supply with the same pedal. If you aren't using batteries and your jack is isolated from the enclosure, the actual direction doesn't really matter for an individual pedal.

What does matter is that industry standard for pedals is center negative, and every single power supply is going to work that way. I would rewire them all. If your son ever forgets, gives the pedal to someone else, etc., then there's a danger of damage. Besides, it's all of two minutes per pedal to swap the leads.
Myself's music & things I make: http://jonpattonmusic.com. My band: http://midwayfair.org. PCBs of my designs from: http://www.1776Effects.com (Bearhug Comp & Cardinal Harmonic Trem); http://www.jmkpcbs.com (Hamlet+ delay & Blue Warbler envelope vibe); Snow Day OD/Flabulanche: www.madbeanpedals.com

mjg

  • Electron Doctor
  • *****
  • Posts: 855
  • Matt
    • View Profile
    • My pedal blog
Thanks for the replies.  I'll rewire the pedals I've done - seems the safest thing to do, if only for compatibility with other peoples' power supplies. 

Matt.