mA???

The rating on the power adapter is a maximum. You should be able to use it with only a 300mA load. I use a 1300mA adapter on a unit that's only 800mA all the time with no issues.

Electrical experts can correct me if I'm wrong, but it works for me.

One important thing is making sure the polarity is the same or else you can blow the circuit. You know that little tip/ring diagram near the power source jack?

 

well, here's tho lowdown:

Firstly, unless your 500mA adaptor has the word "REGULATED" on it somewhere, I wouldn't risk it, because if it's unregulated, it just pumps out 500mA at all times. But if it is regulated, it will just give out what the appliance it's powering needs, anything up to 500mA.

As for polarity, on your pedal (next to the power input) it will have a symbol that looks like this:

meaning it has a positive polarity,

Or this:

meaning it has a negative polarity.

There will also also be a symbol on the power adaptor, if the symbols are the same, then it is safe to use the adaptor with the pedal. If not, don't even plug it in!

so, to recap: if your power supply has the word "regulated" and a symbol matching the one one your pedal, it's safe to use. If not, I'm afraid you'll have to buy a new adaptor, or go to your audition without effects.

 

Batteries?

 

Oh yeah... that too! That's good to know.