Car Stereos: Car Speaker Crackle/Buzz, alpine amp, infinity speakers

Question
I have a dual head unit, infinity speakers, and an alpine amp. Ever since i have had my head unit i have heard a very quiet crackle/buzz noise that does NOT vary upon increasing or decreasing volume. Even when the car is off (battery) the noise is still present. Now that i have added an amp, the noise is louder and more noticeable. I have regrounded the head unit, amp, and reassured proper wiring. It is NOT the alternator, nor RCA's. Could it be a bad unit?

Answer
Joe, it could be a bad unit.  If the car is completely off, and you still hear the noise, your headunit is crossing power from the constant power to the switched power side.  To check this as a problem, move the constant power wire to the switched power wire.  So, the constant and switched wires will both be wired to the same wire.  Then, with the car power off, you should not hear the noise.  Once you turn the car on, you should hear the noise again.  If you do, the unit is probably bad.  If you do not hear the noise, then there is something wrong with the constant power wiring, somewhere.  Hope this helps, Scott