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I am having some major troubles. I installed a custom sound system into a C5 Corvette. The deck is a KVT-7012BT Kenwood ( I used speaker wire to ground the RCAs). The speakers are Pioneers; two front 6x9 and two rear 6½ with a dual self-amplified sub box. The speakers are run by FCAs through an Alpine KTP-445U head unit powerpack amp. The sub box works fine. The system sometimes will sound amazing. But after I get it sounding great I will turn off the car, come back the next time and it sounds miserable.

The sound is not an engine whine. It is associated with bass. The speakers muffle or crackle under bass at ALL volumes. So if I have the volume turned on high it is noticeable, if I have it mid it is VERY noticeable, and low it is still there in the background. It almost sounds like the speakers would if they were blown, but all four speakers have it and if I get it working right you can tell the speakers are in great shape.

The strangest part is I try to adjust the gain on the amp and after a few tweaks it sorts itself out, then when I get back in the car the next time it sounds awful again.

It also pops slightly, and randomly blows fuses.

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I checked out the owner's manual on both units. The primary thing that I noticed was they said "Do not put any conductive near the RCA plugs as it will cause a short circuit" The RCA plugs are already grounded internally to the audio circuitry (a floating ground or audio signal ground-I believe is the technical term) as opposed to a power supply ground. The signal levels in the RCA connections are at millivolt levels.

The gain adjustment on the amp should be carefully adjusted as the input of the amplifier will be overloaded causing distortion. The audio source dynamic range (min low- max high levels) could damage the speakers as well as your hearing.

Similarly, the speaker wiring is the same way, as each speaker has its own individual ground connection. Do not ground either one of these to the vehicle chassis. Both units have discrete power input and power ground connections - only these should be connected to the chassis and power source. Make sure you follow the wiring diagram for each speaker, as mixing them up could affect the balance (left/right) and fader (front/back) functions.

When connecting the speakers, be mindful of the polarity +/- . Reversing the connection will damage the speaker voice coil.

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  • I had switch and checked polarity of the speakers and they were correct. The RCA cables I originally did not ground however once connected to the plug in were massively distorted with two different pairs. Grounding them to the deck significantly helped the problem. But there is still a distortion in the speakers even when the amp gain is all the way down. I grounded the amp and sub to a factory ground spot so the ground is strong.
    – Nick Ted
    Jun 1, 2018 at 14:26
  • Could there be a problem with the ground with the wiring harness? I had to get creative and wire strait into the fuse box for the ignition switch as it was not compatible with the harness
    – Nick Ted
    Jun 1, 2018 at 14:29
  • So update on the situation. I have double checked the whole system and made absolute sure that there are no interferences with power wires and speaker wires. I then unplugged the amp and wired the speakers directly to the deck. IT SOUNDS HORRIBLE!!! There is something causing this problem stems from the deck or wiring of the car. Any suggestions on what could possibly be wrong inside the car wiring itself, or is it just a broken deck?
    – Nick Ted
    Jun 1, 2018 at 18:33
  • Does the deck have a line out level (RCA line) adjustment. If the input to the amp is too loud it will overload the input of the amp and cause distortion.
    – Old_Fossil
    Jun 2, 2018 at 6:18

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