Hiss coming from speakers after installing Panasonic HD radio M+T Fixed

[Gregory J]

Need a little help I installed the Panasonic CQ-CB8901U HD radio and get a low hiss in the speakers. It's happens whether the car is running or in Acc position, AM/FM/CD. does not change in volume when I accelerate or when I increase volume of the unit. I turn the volume down then it's more apparent. I have the Moon + Tunes package and am wondering if it may be a gain problem out of the amplifer (is there a gain adjustment?). I have the ground wire into the harness and not the chassis. The rep from Panasonic was lost also. Only deviation from Panasonic instructions was ground to the chassis.All suggestions would be greatly appreciated. With my thanks to GMJAP found one of his solutions on this site I used the PAC OEM-2 universal 4 channel line out converter / factory amp interface glad you were around, I still have my hair. Little more expensive but heavy duty.

[ProtonXX]

I have the same problem after installing my DVD head unit. Hiss is unaffected by volume, car/on off. Only muting stops the hiss

[Gregory J]

Try the out convertor/factory amp interface. This installs in the line between the radio wiring harness. since the radio is aftermarket I assume you had to put a harness convertor in it. You will have to recut the wires and install this unit inbetween. The convertor has gain controls built in which you will need to adjust to get the hiss out. I'm assuming you had the moon & tunes high power system in the Vibe. The amp for the unit is below the seat and does not have a gain control so this is the only solution. your running two high power units so it needs to be balanced. a less expensive unit can be found at Walmart, but I went premium for my peace of mind.

[Jahntassa]

Yeah, you basically need a high-level gain matcher. The M&T amp can't take too much power going in, and it probably isn't the right resistance to the radio, so there's hiss.