Positive Ground 9v Power Input

Frequently asked questions regarding powering your pedal.

Positive Ground 9v Power Input

Postby Sadcadaver » 01 May 2012, 14:17

I'm building my first PNP circuit (a Toecutter), and obviously I'll have to wire it differently. I want to use an ordinary 9v power supply, and came accross a couple of wiring diagrams at General Guitar Gadgets that seem to fit the bill:

http://www.generalguitargadgets.com/pdf ... np_dcj.pdf
http://www.generalguitargadgets.com/pdf ... dcj_gi.pdf

What I want to know is, whats the difference between these? In simple terms if possible.

Sorry if this seems like a stupid question...
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Re: Positive Ground 9v Power Input

Postby Govmnt_Lacky » 01 May 2012, 15:25

Both of the layouts that you linked are for POSITIVE GROUND circuits. These are typically utilized for circuits containing PNP transistors.

The only difference between the layouts is that one of them utilizes INPUT GROUNDING. This means when the effect is disengaged via the 3PDT, the circuit input is grounded. Sometimes this helps with unwanted "clicking" or "popping" when you initially engage the circuit for use.

As for the power supplies, you can use any typical wall wart to power the effect however, YOU CAN NOT use the same power supply with other NPN circuits (most other effects) at the same time. You would need a seperate wall wart or isolated power supply for each.

In the simplest terms... you would need a wall wart for your PNP positive ground effect and you would need a seperate wall wart to power your other NPN negative ground effects.

Of course, you could avoid the second wall wart by building a voltage inverter like madbean's Road Rage circuit. This will provide the -9V supply for the PNP circuit from the same wall wart you use for your other NPN circuits.

Might seem confusing (as it did to me at first) but it is actually quite simple.

Hope this helps :D

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Re: Positive Ground 9v Power Input

Postby bato001 » 01 May 2012, 17:24

The difference between the two diagrams is really in the wiring of the 3pdt switch.

One way to wire the switch is intuitive and easily understood, but does not ground the circuit input during bypass: (http://www.generalguitargadgets.com/pdf ... np_dcj.pdf).

The other way grounds the circuit input during bypass but is more complicated and requires an extra jumper (http://www.generalguitargadgets.com/pdf ... dcj_gi.pdf).

Both wiring diagrams work equally well, and both require the use of a separate power supply.

See this page of the Tonebender MKII thread regarding a short discussion of a way to wire the pedal to play nice with a Daisy Chained power supply: viewtopic.php?f=19&t=920&start=420
"Ever wondered how some of your favourite guitar players got their tone? Me too. Probably a good amp and lots of practice." Little Lord Electronics Homepage

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Masuto (30 May 2014, 12:59), Sadcadaver (03 May 2012, 14:10)
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Re: Positive Ground 9v Power Input

Postby Sadcadaver » 03 May 2012, 14:11

Thanks, both answers were very helpful!
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