I have an headphone amplifier that is missing a power supply, it requires 9 volt 750 mA ac, I have a 12 volt 830 mA ac power supply with the proper tip, will it work or is the 33% higher voltage, too high?

That's 33% higher,and 9 volts is 9 volts not 12 volts is 9 volts.

Yeah, sorry about the 25 percent, brain fart. Are you saying it shouldn't be used at 12 volts?

It may work real good for a real short time!!:laughing:

Go to Radio Shack, they aren't that expensive...get the right one.

It's impossible to say unless someone knows the product very well. As a general rule...don't push your luck unless you have better information.

As an example, we have a product that is listed for 9 volts but will operate just fine at 35 volts max. Another product is also listed at 9 volts but 12 volts would be pushing the limit.

Not if it requires 9 volts.

Yeah I didn't think I should use it but I thought I would ask. Thanks for the help I'll pick up a matching power supply at radio shack.

My guess is that it would probably work, but I wouldn't risk it unless you just don't care about destroying it. Most types of amplifiers aren't too picky about input voltage. The input voltage determines output power (indirectly, by changing gain) so it would be louder and also produce more heat. It's unlikely that there's less than a 33% voltage overhead on the components in the amp, so 12V would probably not immediately damage it. However, many "12V" power supplies have actual output voltages that are more like 14-18V when unloaded. So you could be running almost double the nominal voltage, and that might be a problem.

Yeah this particular power supply has a voltage output of about 14.5 volts unloaded.