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 Post subject: Positive Ground Question
PostPosted: Tue Apr 16, 2019 11:25 am 
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Hello,

I've built my first positive ground pedal on a bread board. It's a simple Fuzz Face built off the original schematic, it works wonderfully but I have a few questions. I have wrapped my head around why I cannot daisy chain it, as you introduce a positive voltage to the negative voltage ground of the other pedals. My questions are as follows.

- If traditional negative ground pedals were daisy chained to my positive ground fuzz face, could it damage those other pedals as it would introduce 9V into their grounds?

- Why am I able to connect my positive ground pedal to other normal pedals via patch cables as long as the power is isolated? Since the input/output jack's ground is referenced to positive ground voltage, couldn't this potentially send harmful positive 9V voltage out to my other pedals via the ground? Since jacks are typically grounded to the enclosure with the rest of the pedals ground, wouldn't this be problematic?

Am I supposed to be isolating the positive ground fuzz face's input/output jack ground?


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PostPosted: Tue Apr 16, 2019 11:50 am 
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Positive grounding has always been a challenge for me to sort out mentally. Below is a link to a very informative article you may find useful, as I did. The issue, as you have stated, is the circuit's ground polarity, not the polarity of the DC jack. While some positive ground pedals do use a center-positive jack, all of BYOC's positive ground pedals still use the customary center-negative configuration.

http://stinkfoot.se/archives/532

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PostPosted: Tue Apr 16, 2019 11:52 am 
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Thanks! I'll check out that article and see if it helps. I decided, when I build this pedal, I will use a traditional negative center pin set up. What's really leaving me scratching my head is why the guitar's ground signal doesn't become problematic with other pedals. Everything I've read says, that as long as you're not connecting the pedal's power, you can link up your other boxes.


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PostPosted: Tue Apr 16, 2019 3:57 pm 
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Ok, read the article, let me know if my logic is sound.

When the two pedals are linked up by patch cables, but on separate power supplies, 9V from the positive ground pedal IS contacting the negative ground pedal's ground via the jacks. It doesn't matter though because they're on different power supplies so it doesn't complete a circuit, hence no ground and no short. Basically no voltage flows from the positive ground of one pedal to the negative ground of another?

It would be the same idea as plugging the anode of an LED into the positive side of one 9V battery and the cathode into the negative of another battery... it wouldn't complete a circuit and voltage would not travel.

Am I crazy or on to something?


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PostPosted: Sat Apr 20, 2019 3:22 pm 
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Just bumping this.


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PostPosted: Sat Apr 20, 2019 3:31 pm 
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Yeah, if you use two power supplies like that you are fine.

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