type 44 stereo, is this a bad ground?

[CL Wong]

I just installed a new amplifier into my 200Q20v and
I'm getting all kinds of noise that my old dead
amplifier didn't make.

Head unit is grounded to the same seatbelt bolt that
the amp is grounded to.

pulling the RCA cable from the amp silences the noise.
pulling the RCA cable from the head unit also silences
the noise.
pulling the antennae does not silence the noise.

with the engine off, I can hear the indash cd
mechanism doing the track seeking thru the speakers.

with the engine on, I get a buzz with an engine speed
related whine behind it.

old amp: kenwood 40wX4
new amp: usacoustics 60wX4


so is this somekind of ground issue?

Do I need to add a noise filter to the switched 12v
and constant 12v to the head unit?

thanks in advance.

Chi

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