h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I've bought a portable sequencer on ebay that requires a (not supplied) mains adaptor, the current *cough* version of which is available online (Input 120V, 60 Hz, Output 700Ma). The sequencer needs a DC supply of 9V.

The manufacturer makes the usual point of not attempting to use any but the specified product, but I was hoping to get away with using one that supplies the same 9V DC (Input 240V, 50Hz, Output 500Ma).

Bad and wrong?

As long as your adapter gives out the correct voltage (in volts), and is capable of giving out at least as much current in milliamps, then you're OK.

But be warned that there are a number of different plug types at the 9V end. Some adapters come with a range of differnt plugs you can put on the end, which makes it easy. Even then, there are ones with the positive in the middle and ones with the positive on the outside. So be careful.

Looking at your spec, the manufacturer's supply gives out up to 700mA, while the one you are looking at can only give out 500mA, so that's not enough. But if you look at the device you are powering, you may find it doesn't actually need 700mA, which is rather a lot.

Presuming you're in the UK, the 'official' version you quoted looks like an American standard and wouldn't work properly on a UK mains supply.

There are only two slight worries...

1) The 'official' version kicks out 700mA at 9V DC, whereas the one you want to use is only 500mA...

2) The polarity of the connectors might be different.

My suggestion would be to get hold of a slightly larger 'generic' mains adapter - there are plenty on the market that you can alter the output voltage and the polarity of the connectors.

D**n - too slow, as usual....

Thanks guys. I'll get a multi-headed one. I tested it with another (otherwise powering a digital delay pedal) and though I had to swap the pins over it worked fine. I didn't check the milliamperage of that one, but was given to understand it's more important not to overdose it than underfeed it.

Gnomon will probably correct me on this one if I'm wrong... But I was of the opinion that a mains adapter would provide -upto- it's maximum current rating and that the electrical device it's plugged into would 'pull' what current it needs from the power supply.

If you put too much voltage into your sequencer you will destroy it.

If you have a device which needs 700mA and you feed it with a 500mA supply, then it will pull 700mA and melt the powersupply. Possibly. They're often actaully capable of providing more power than they say, as the designers tend to be a bit conservative. But you're better buying one which is officially capable of doing what you want it to do.