Noob Power supply build Question

[DLM]

Hello , I bought a AMZ power supply board . I've started reading the instruction page . What it has is +9v supplies from the board to the output jacks  . It goes on to say to wire the output  jacks with a center negative . My pedals are center negative - serendipity  and boss pedals . My question is ... Do I run my pedals with +9v and wire the output jacks neg center ? I thought I needed -9v to run my neg center pedals . I 'm confused . I got a charge pump to run the -9v . I thought I would need it to change the +9v to -9v to run my neg center pedals . Can anybody straighten this out for me please . Thank you

[jkokura]

Sure, you're confusing +9V with -9V.

Basically, voltage runs on a swing. Consider 0 to be ground in most cases, particularly with pedals. This means that 0 is considered as one end of the swing in some pedals, but can sometimes also be used as the middle of the swing, which only confuses things... sorry

So if 0 is our ground, that means that +Xv is one side of the pendulum swing, and 0v is the other side. So for example, using a typical +9V power supply you'd have a 9V swing from +9V through 4.5 to 0V. However, you could also use a +/-Xv supply you could have a swing from +9V through 0 to -9V which is an 18V swing. Alternatively, you could use +18V through 9V to 0V and achieve the same voltage swing with different numbers involved.

The confusion sets in because some pedals, particularly some using germanium or silicon transistors, use a swing from 0V to -9V instead of +9V to 0V. That's because some of those transistors are built to function that way. They don't necessarily play nice with the standard used by early pedal makers like Roland/Boss and Maxon/Ibanez. They use the same swing though, so you get  a similar performance on them.

With the case of centre ground, that's an entirely mechanical discussion rather than the electrical one above. In this case, we're talking about the plug being used, not the voltage or swing at all. Power plugs generally come in barrel format that have a centre section and a barrel section which connects to a pin and a sleeve respectively. So, when I was talking about ground above, 0V in almost all cases, a centre negative supply or connection assumes that the centre section of the plug, or the pin of the jack, is your electrical ground connection. This leaves the barrel to connect to the sleeve of the jack carrying the +9V.

Some power supplies use a centre negative format, which is what %99 of pedals use, and some use centre positive format, which means the barrel connects to the sleeve for the ground connection.

I hope all of that is correct. I'm still fuzzy on the +/- supplies but I think I have it right.

Jacob

[rullywowr]

Jacob, nice explanation - should be a sticky IMO.

[DLM]

Okay ' Ya ...... ah....... What was the middle thing ??  No , really , I understand what your talking about  after reading it a few hundred times ( LOL ) So in simple terms , old school fuzz boxes and other vintage pedals use -9V power because of the germanium or silicon transistors . The charge pump can be used to do that if needed . I'll use the charge pump for 12v ,15v and 18v  instead . So what I need  to do is run +9v  and wire my output jack center negative and I should be good . Thank you  for the Lesson ! I will keep this lesson in my pedal file to refer back too . This hobby isn't about just soldering things to board and then plugging it in and seeing  if works ! I want to learn how and why it all works .  I greatly appreciate you guys taking the time to help me understand all of this . ONWARD - BACK TO THE BOOKS !  DLM