Power Supply Question

[RobbieAG]

Hi my name is Rob and I'm new to this forum.

I was wondering what would happen if I use a power supply that is rated higher than the effect. For example, I have a 9V 1.3 amp power supply. Can I use it for an effect that calls for 9V 300 milliamp? I also have some power supplies from old laptops. One is 16V 1.88 amp. Will I fry my effects if I use it? The plug in is compatible. If using it is not advised, is there a way to reduce the power output to make it compatible? Thanks in advance.

[Jazz P Bass]

Power Supply

If the effect calls for a 9Vdc power supply that can supply 300 ma's of current, then the 9Vdc rated at 1300 ma's (1.3Amp) of current will do fine.
Some power packs have different polarities on the plug end.
Make sure they are the same as the effect calls for.
Forget about lowering the 16 V power pack.

[loudthud]

There can be no general reccomendations. Most laptop supplies are switchers that can be very noisey. Even small supplies intended as battery chargers are switchers these days. A power supply rated for more current than an effect requires should work but be advised to measure the voltage before connecting the supply. Most effects can withstand probably 15V but there may be exceptions that will be damaged. Many power supplies intended to be battery chargers can put out considerably more voltage than what is listed on the label.

A small voltage regulator could be constructed that would reduce voltages to what an effect wants. You could still end up with noise problems from ground loops.

[Mark Hammer]

The power supply's rated output is what it can deliver when asked to. The pedal may only need a fraction of the current that is available, and that's all it draws from the supply. If you think of it, batteries can also provide a whole lot more current all at once too. But, the circuit only calls for a little taste of that current, so that battery lasts for a while.

Note that power supplies vary widely in the degree of regulation they provide. Ideally, a PS should come as close to pure DC and battery-like power as it can. Simply converting/rectifying AC voltage to something you can technically call DC does not always result in ripple free smooth stable power. Poorer regulation will show up as ripple on a meter or scope, and as hum when you listen to the pedal/signal. So, having a PS that nominally meets the requirements (right voltage, right type of current - AC vs DC - sufficient current, right plug orientation/polarity) may not result in a PS that meets your needs in terms of sonic consequences.

PSs from computers are generally switching power supplies. If they are properly filtered, they can work fine for audio equipment. However, there can sometimes be audio issues when digital pedals are powered by them, and particularly when two or more digital pedals are sharing the same supply. It's not always a problem, but it is something to keep an eye/ear out for.