Reversing the polarity of power jack to be use for positive tip of the pedal?

[rogeryu_ph]

DIYer,
Hi, I'm searching every thread on power supply on this forum but I could not find the answer to my question. I have a positive regulated 1A power supply with negative tip to power up my Ibanez and Boss pedals and  I have this DOD fx40 equalizer which I use it with different adapter (500ma) co'z it positive tip configuration. Some say that I could only reverse the polarity of one power jack and can be use it to my DOD so I don't need to use two power supply no more. Is this true and safe? or m I confused?
I have read that:
Negative ground = Positive regulated voltage supply
Positive ground = Negative regulated voltage supply

Roger

 

[GibsonGM]

Hi Roger,

It's my UNDERSTANDING that you could just reverse the connections to the jack on the DOD (at the circuit board), and that the power supply should work.  All you're really doing is reversing the ground and power rail to match the output of your adapter. This assumes that it will provide the necessary current, however (if it needs 500mA, you're all set).  And the regulation may not work the same - but I don't BELIEVE this is an issue - it just wouldn't work right if that is the case.  Then you would have to put the jack back the way it was. 
 
Positive ground is just a reference point - if your incoming voltage respects the internal wiring, everything should be fine regarding ground, therefore you reverse the jack (being SURE the tip is positive, and the tip on your existing adapter is NEGATIVE, before the reversal!).

I'm not sure that there's enough information here to make the call from an engineer's viewpoint (I am not an electrical engineer).  Personally, I would try it, but that doesn't mean it will work!  But I like to experiment ;o)  If someone more knowlegeable would care to comment...?

[rogeryu_ph]

Hi GM,
Thanks.. The 1A positive IC 7809 regulated power supply I built (NO CENTER TAP 12VAC) has five output jack which is negative tip that is compatible for BOSS and IBANEZ co'z they are negative ground. What i'm planning to is to reverse one of the jack so that I could use it to DOD positive ground. This I may not need to use two or separate power supply for DOD fx40 only the 1A power supply. I'm not going to reconfigure the pedal only one of the 1A power supply output jack. I'm reluctant to do it still I'm in doubt maybe it's not safe. Oh the DOD fx40 indicates at the back "USE POSITIVE GROUND" Thanks GM.

Roger

[Mark F]

Hi Roger. You are correct. You can just reverse the polarity of one of the jacks to get a negative ground, positive tip. Just make positive SURE that you DO NOT plug that jack into one of your Positive ground , Negative tip pedals. Good Luck!

[darron]

from my understanding it would only be safe to do if the jack is isolated (assuming it shares the same grounding through the patch cables, which would be like shorting the same powersupply).

I don't know why nobody has suggested this one to you yet, construct a cheap effective power adaptor for that one pedal! tht's the best option, you'd use the same power supply without changing your pedal!

basically, get a 2.1mm barrel socket and a plug and and wire them up with the polarity switching between them. if you want to make it look really neat you could use some small black heatshrink along the two wires. It'll look like you bought it...

[rogeryu_ph]

Mark and Darron thank you for you prompt reply. I just want to clarify one thing, the 1A power supply is positive IC regulated  and the negative is not. If I will reverse one jack to be use in my DOD fx does this means the supply I'm feeding to it is still regulated? Pardon for my ignorance   

Thanks also to you GM,
Roger

[Harry Palms]

Regardless of what the labeling may say the DODs aren't positive ground circuits. They are the standard uni-polar zero volt ground/positive 9 volt types of circuits like most everything else we build except the PNP type circuits, bi-polar effects, etc.  The only difference is that DOD took the positive 9 volts and ran it to the center pin and ran the zero volt reference line to the outer pin. The "type" of voltage is the same - positive 9 volts with a zero volt "ground" reference.  There is no negative voltage supply involved. DOD just set it to enter into the pedal through the opposite pins of what the Boss and Ibanez did. You could just as easily set the DC power jack into the DOD back to the standard way right at the circuit board making it a center pin 0 volt ("negative") with a cut and paste approach at the board. You wouldn't have to mark and remember your one lone wire which you had reversed to be center positive, outside zero. Rewire it at the PCB and just confirm prior to plugging it in that you are, in fact, getting the expected voltages at certain points e.g.  0 volts at an opamp pin 4 and 9 volts at pin 8, say.

The regulation concern is a non issue. You have a steady regulated positive 9 volt supply. You can get it into the pedal any way you choose.

[rogeryu_ph]

Hi Harry, Thanks for the great revealing information you provided. I just know now that DOD is a real negative ground !!!  They only  reversed their pedal power input configuration if I got you right?
Roger