PNP pedals mixed with NPN pedals on a 1 spot daisy chain?

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pikingrin

pikingrin

what is this?
This may not be the appropriate spot for this...if it needs to be moved then do what you must. :)

I'm getting a few pedal kits for christmas this year and I've been busy printing off the info for them. I'm fairly certain that one has a PNP transistor in it so I've been doing some digging around as to what could happen if I forget and plug my 1 spot into it (or a power supply when testing) that isn't the right polarity. Apparently, if it's in line with any NPN transistors, everything will short to ground and no pedals will work. No big deal, as long as I can remember which is which (will probably mark it just to be sure).

But, I have also read that I can change the way the power input jack is wired and I can daisy chain it with any "standard" NPN pedals. Is that true?

I've also seen that 1 spot makes a reverse polarity adapter (shown here) but it only specifies for use with keyboards, etc. Would that do the trick instead of wiring the power input backwards?
 
Hi,
You should mark the pedals positive ground for your own reference.
It is possible to add diode protection, though, so if the wrong type of supply is offered no damage will be done.

The adapter you show swaps the pins around but that doesn't necessarily relate to being a PNP or NPN pedal.
Some manufacturers just have the pins the 'wrong' way round.

The short answer is that you can't use both types of pedal in a chain from the same supply.
I'm thinking you can run them from a bipolar supply, though, where the 'normal' pedals use 0 to 9V and the others use -9V to 0V.
Would like confirmation on that....don't take it as fact. ;)

I thinking it's right because my little DIY amp is positive ground and I used a conventional treble booster with it, running off a bipolar supply.

Maybe read here and here?
 
Or you could use a voltage inverter for the power supply.
 
How you wire the DC input jack isn't really the issue. If it was me, I'd wire it center negative just like everything else so I didn't need special wallwarts that could kill my other pedals.

The real issue is which "end" of the supply coming through that jack is connected to the audio jack sleeves. It is at least theoretically possible to isolate those sleeves from supply with capacitors if you needed to.

Not all PNP circuits are positive ground. Details matter in this case, so if you've got a schematic...
 
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What exactly are the PNP transistors? If they are bog standard silicons, BC186, BC2I4L* then just swap them for the NPN compliment . BC107/8/9, BC184L*.

If they are some supposed Germanium "whunderkinde" then a compliment might be harder to find and a bit pricey.

*Be very careful of the pin outs on these. Can be one of three versions!

Dave. (I am pretty sure Autocorrect turned "cons" to "cones"? Thank you Msoft for potentially making me look a t***t!)
 
Steenamaroo said:
The short answer is that you can't use both types of pedal in a chain from the same supply.
I'm thinking you can run them from a bipolar supply, though, where the 'normal' pedals use 0 to 9V and the others use -9V to 0V.
Would like confirmation on that....don't take it as fact. ;)
Click to expand...

There are a lot of wall warts out there that let you reverse the polarity by simply plugging the barrel plug backwards into the wall wart leads. They usually work well with pedals, and I'm pretty sure they're all single supplies, as there are only two DC leads and the reversal works by swapping the leads. I highly doubt the type of transistor in the pedal has anything to do with it. I'm not sure why the OP's idea of wiring the power jack on one pedal backwards won't work.
 
diggy_dude said:
There are a lot of wall warts out there that let you reverse the polarity by simply plugging the barrel plug backwards into the wall wart leads. They usually work well with pedals, and I'm pretty sure they're all single supplies, as there are only two DC leads and the reversal works by swapping the leads. I highly doubt the type of transistor in the pedal has anything to do with it. I'm not sure why the OP's idea of wiring the power jack on one pedal backwards won't work.
Click to expand...
There's a HUGE difference between the polarity of the actual jack and the polarity of the circuit itself.

The DC jack on most pedals is center-negative for some stupid fucking reason that I think has to do with Boss wanting to sell their own wallwarts and make an easy profit. If you're building the pedal, there is NO good reason not to observe that convention (as stupid as it seems) because all of your other pedals are going to be center-negative and carrying a separate wallwart - or even cable or adapter - is stupid, and if you mix them up (whether plugging in the reversed one to a normal pedal or a normal psu to a reversed pedal), you'll destroy either the pedal or the wallwart or both. So, wire the jack itself to be center-negative ALWAYS.

How that jack connects to the rest of the circuit is a completely different deal. Some pedals, for whatever reason, are set up as "positive ground", which means a couple of things that we don't need to worry about, but what does matter to us is the fact that usually the most positive voltage from the power supply (whichever part of the DC jack that comes from - should be the outside barrel if you followed my advice above) is connected to the pedal's chassis and the sleeve of the in/out jacks. This is generally fine as long as it's got its very own (two wire) power supply.

The problem comes in when you try to daisy chain these things off the same supply as other, more conventional, "negative ground" pedals. Those have the most negative part of the supply connected to chassis/jack sleeves, and that's fine too...until you connect those pedals via a patch cable. Now you've got the "top" of the supply connected to the chassis of one pedal, to the chassis of another pedal which is connected to the "bottom" of that same supply. The power supply is shorted so that neither pedal actually gets power, and it tries to drive infinite current through the loop. A OneSpot or other decently-designed PSU will protect itself by limiting that current or shutting down, but unregulated supplies will more likely just burn themselves up.
 
Great info! ^^

kip4 said:
Or you could use a voltage inverter for the power supply.
Click to expand...
I thought so. That'll give -9 0 and +9, allowing 0V to be the common ground for the pos-ground and neg-ground circuits.
 
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