T500D13 Power Supply Amp?

look here for the formula.

Oh is this a transformer or a power supply or what? a better description maybe?

the part number you give comes up as part of a parts number for transformer.

a picture would help.

it is a transformer the whole thing is 9070t500d13 when I searched the whole thing I found nothing we used this transformer and a rectifier to create a dc power supply thank you I will look up what you gave me

The thing that is curious is how a 500VA unit is going to supply a 3kW load.

It may work fine until the music is turned up. (Makes me wonder why a 3kW audio amplifier is needed.)

I do not see very much detail about this transformer that makes me comfortable for it to be used as the OP intends. I suspect that the 12V output rating is the RMS AC voltage while driving a 500 watt load. If this is true then the peak voltage will be about 17V. Using just a rectifier and capacitor filter puts the DC voltage at about 16.5VDC. When not driving 500 watts the output voltage will increase to probably no more than 20% higher but it will change depending on the output impedance of the transformer. (I find it easiest to use the Thevenin equivalent for a transformer.) Directly connecting this unregulated supply to an automotive 12V battery will boil battery fluid very well. A battery charge control circuit could be placed between this supply and battery and work quite well though.

Similarly this unregulated supply could likely drive only an automotive audio amplifier but the input voltage range that the amplifier is rated to handle must be considered. Now since most music has bursts of loud passages instead of a consistent loud section this might be acceptable for many venues. Many loud bass notes will overdrive this supply. Using this supply to charge a battery while driving the amplifier will extend the time it takes for the bass notes to overwhelm this supply but it can still happen.