Guitar effect power connector polarity?

[Rhodesplyr]

In general, it seems to me that the majority of DC wall-wart power supplies made for consumer electronics use positive-tip/negative sleeve barrel connectors--except for most, but not all, guitar effects. (The Fulltone '69 Fuzz being one exception.)

My question, as a keyboard player: How did this end up being the case? My guess would be that it had to do with PNP transistors used in early guitar effects, but I thought I'd ask.

Source of the question: a guitar player friend of mine asked me to check out his Fulltone Fuzz because it didn't work with his pedal supply. I had to point out to him that it said "Positive Tip" on the case. If all else fails, read the instructions

[Enzo]

PNP? Nah.


Most DC jacks are not grounded until you wire them that way. In other words, your 9v adaptor makes 9vDC. Once inside the pedal, you can wire it for positive or negative as you see fit.

It is electrically not an issue then. But just thinking about it, the barrel is the contact that can be switched. The FX pedals that can use an adaptor also usually can run on battery too. SO by running the negative through the tip and on to ground, we have the positive on the sleeve, which can switch off the battery.

[Mick Bailey]

Quite a few FX pedals from the 70s and 80s originally used a non-isolated 3.5mm mini jack, Barrel negative (grounded to the case), tip positive. Still with the intention of battery/PSU operation (such as Jen pedals). The isolated 2.1mm connectors with centre-negative seems to me to have arrived in pedals with Boss and their ACA supply. It was a rarity in those days to get a factory-wired connector with that polarity. Roland probably saw this as a way of commercially differentiating their PSU as I can't think of any reason why they couldn't have switched the battery negative and kept to consumer polarity convention of a positive tip.

Apart from compatibility, the biggest nuisance with a positive barrel is the ease of accidentally shorting it against grounded metalwork with a daisy-chained supply.