P <> N ... that is the question?

Frequently asked questions regarding powering your pedal.
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Kregg
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Post by Kregg »

I read comments and articles all of the time that say something to the effect of, "positive and negative grounded pedals can't be daisy chained."
So, to all of the closet geniuses out there ... is there a way to work these misfits into a pedal chain without complications?
Surely someone must have come up with a gadget by now ... right?
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Post by Hides-His-Eyes »

MAX1044 IC.
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Post by JiM »

Kregg wrote:I read comments and articles all of the time that say something to the effect of, "positive and negative grounded pedals can't be daisy chained."
You actually can do this, as long as the power supplies are completely isolated (ground referencies floating relative to each other).
This can be done with batteries, separate AC/DC converters, or a "power brick" with isolated channels (most aren't).
Or you can use a gizmo like these, which are basically isolated DC/DC converters :
http://www.godlyke.com/_product_88356/G ... D_ISOLATOR
http://www.thegigrig.com/acatalog/TheGi ... ttery.html
Hides-His-Eyes wrote:MAX1044 IC.
Of course, having a proper -9V power supply enables sharing the same ground reference, instead of shifting things up and down and relying on DC-blocking caps at the input and output of each pedal.
I only give negative feedback.

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Post by RnFR »

or you can simply flip the circuit upside down using the negative rail for ground and the positive for power- the same way pnp transistors are incorporated into npn circuits. some people have reported motorboating low end oscillation, but with proper power supply decoupling, I've never had a problem.
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Post by DrNomis »

I just spent some time helping a guy called Chile,fix a bad hum issue in his Tonebender Professional Mk 2 pedal,it turns out that his pedal used three Ge PNP germanium transistors,anyway,i discovered the source of his problem after looking at the schematic he used to build from,you know what I noticed straight away?,whoever drew the schematic,made some fundamental mistakes when drawing the schematic so it would use the negative earth system,I'll explain.... :)


The point in the schematic which should have gone to the negative battery terminal,was connected to circuit ground,and the battery positive was connected to circuit ground also,and it was drawn in a way that made the volume control look like it was connected to circuit ground on both outer solder lugs... :)


So,I posted a pic of a corrected schematic for him,he PMed me saying thankyou for helping him out..... :)
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Post by DrNomis »

The moral of that story is that sometimes it is better to keep a pedal,with PNP Ge transistors,wired so that the ground is positive,and just power it with a battery,i do that all the time and it just works fine,even when I chain negative grounded effects with positive grounded effects,and relatively few hum issues too.... :)
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Post by JiM »

RnFR wrote:or you can simply flip the circuit upside down using the negative rail for ground and the positive for power- the same way pnp transistors are incorporated into npn circuits. some people have reported motorboating low end oscillation, but with proper power supply decoupling, I've never had a problem.
That's exactly what i did with my RangeMaster clone.
It's a bit noisy (hiss), but i guess it's just the fault of the old OC75.
I only give negative feedback.

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DrNomis
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Post by DrNomis »

RnFr,


Hey thanks for bringing this to my attention,much appreciated.... :)
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Post by DrNomis »

I guess that this is something that's going to be a perenial problem.... :)
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