tricky noise question

Ok this problem has been bugging me for about a month and i cant figure out what the hell is wrong. The problem is when my HU spins up the cd i can hear the motor whine and the laser movement coming out of my subs. So far i have rewired power and ground to the HU, checked ground on the HU and amps, then referenced it to batt voltage. Tried replacing the amps, and running new rca's. nothing has worked HELP!!!!!!!!!!!1

I'd try another head unit. BTW, which one are you using now?

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the12volt • Support the12volt.com

I find it has to do with how high your gains are set. I've just redone my gain setting in my car and i've got the same probably where as before it was noise free.... well maybe just quite enough to not be noticable.

ok my HU is a kenwood kdc-mp-919. the gain on the amps is about 1\4. i have tried messing with the gain on the amps. the noise remains. even when i turn the NF to -15
and the volume to 1 the noise is still at the same volume.

Oh i forgot to mention that the noise occours on the NF front and rear preouts.

Well next thing to do is to check all connections on the amp and make sure you've grounded it to the chassis and the point has been sanded back. If that doesn't work try another location to ground too. Do you have a multi-amp system?

i believe that this is caused by a ground loop.  is the ground of the head unit next to your car fuse block, or a major power wire.  is so, try to make the ground as short as possible, but not close to fuses, or major power wires.  i believe the pre-out voltage is 1.87v, so i would set the gain on the amp around that level.  if you have two amps (or more), try using a ground block (like a distribution block, but for the ground, as it has no fuses.)  if all else fails, the HU might be to blame, and i might get it checked out.

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toyota echo...perfect sound named vehicle

yes i have two kenwood 600 watt amps each running one alpine type r. the ground reads 0 voltage drop from batt voltage. could it be a bad pre amp in the HU? and is there an inline filter i can use on the rca's until i can get a new HU?

hey sometimes no matter how hard you try...it is almost impossible to eliminate ground noise...there are SOOOO many reasons that you could have it.  go to your local sound shop and ask for a gound loop isolator.  it should cost about 20 bucks.   it has famale rca's on one end of the box and male on the other.  plug the rcas coming from the amp in one end and the other end plugs into the head unit.   that should work.

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try putting the volt meter on the vdc setting, putting the red lead on the amp negaitve post, and the black lead on the batt post neg. when the system is on.  you should get a voltage drop.  like .1v or something.  but it should not read zero. to get a fairly steady reading, turn the volume all the way down.  also i think that these model HU's allow you to turn off the internal amp in the HU.  do that if you can.

TO c.c: the pre out voltage on this HU is 4.5 volts. which is where the gain is set. the power is ran away from the fuse block and strait to the batt.

Ok please explain the last post about the voltage drops. would it be better to use a scope to try to isolate the noise? hey thanks for all the help guys

umm how do you have it wired b/c i was told if u run all of ur other wires ie rca and the like next to the power cable u can get a lot of screwed up noises

Power and signal leads are ran on the opposite side of the car, they cross one factory harness at 90 degrees. anyway the noise i am getting is not the typical vehicle induced noise. it only appears when the cd player is working. the radio is clear. like i said this noise is a pain in my A$$

try testing it on another kenwood...... did you buy it in town? if so go back and tell them its f**kin up and u wanna excange or contact kenwood about it

i have an extra question, was is it said that running rca's near the power line is bad? mine run on top of each other with no problem.

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Quad L Handyman services

well iwas talkin to some install guys at a couple of dif places in town here and thats wut they all told me