Most alternator whine is caused by ground loops. There is likely a bad ground at the Amplifier or at the Receiver. These two grounds need to have the same potential for ground. The receiver ground should go directly to chassis with the shortest distance possible. If the noise varies with volume then it is probably not a ground loop, but from the power to the radio, which could be fixed in most cases by running a wire (fused) direct to the battery. There are plenty more possibilities. It could be from the RCA cables being too close to the power wire to the amp. An easy test would be to turn the system off, disconnect the RCA cables at the amp, turn it back on, if it is still present then that is not the problem. But not to get to carried away, if you paid someone to install it, you really should be bringing it back to them, this is there problem, not yours.
