i've decided to post in here, rather than the UK forum about my ICE issues, since theres probably alot more collective knowledge...

i bought a new system at the weekend (amp, speakers, and wiring kit, HU is 3-4months old)

long story short, im getting interferance with engine off (ignition on) and alt whine with engine running.
i've managed to get it noticably better than it was, but im still getting interference.

the inital issue: seems to be some major ground problem.
i've now narrowed it down to wiring/car side, rather than the new kit itself.

i've ran in a test wire from battery to AMP, and then onto the HU (using the amp's power connectors to join the wires) and it's reduced the interference by around 75%, still slight interference and still alt whine though.
so i add in a battery cable from the HU chassis, to the handbrake 12mm bolt, and the interferance increases (still have HU connected to battery).

kit:
Pioneer p7900ub (3-4month old)
JBL 6.5" components
JBL 80w rms amp
unbranded wiring kit (but the 'test' wiring eliminated this as being the cause)

i've added in 2 earth cables to the battery aswell.
using the orginal battery>chassis cable, added in another that runs parallel to this, and a 3rd using that same bolt, to the engine block.

anyone give me some light to what the problem might be?

 

ok, long story short (again), i've been tinkering.

wired it all back into car and sorted the previous owners wiring out - soldered the radio wiring to the car-side ISO connector so no push terminals for HU power.

HU 12v+ all wired via car's radio wiring.
HU ground = car-side ISO connector run on new wire to the amp's earth point (avoid earth-loops). this is the only ground the HU has.

fact(??) - connect HU side RCA center pin to any ground = should be 0 noise from an amp'd speaker.
so based on that,
RCA > car wiring ground = noise
RCA > amp's ground point (through this new wire i've put in) = noise
RCA > HU chassis = noise
RCA > HU RCA = noise
RCA > Ipod with RCA adaptor (ipod on batteries) = no noise and 100% perfect; no alt whine either.
Ipod > direct into amp input = no noise; 100% perfect

hope that makes sense.

 

usual culprits are inadequately shielded RCAs run near a noise source
or bad amp ground.
it's not totally clear to me whether you've done this already, but if you
can hook up your ipod to the far (headunit) end of the RCA's you'll have
the answer as to whether the RCAs are picking up noise. which route
do your RCAs follow?
where is your amp ground point? is it totally paint free? have you used
an ohm meter on your amp's ground wire?

 

LoL...

Something we actually agree on?


Check to make sure there's < 4 ohms between the amp ground point and the battery. You might want to consider putting in a separate power line to the HU, not necessary, but it will give the HU cleaner power and might help a bit with the problem.

Where are your power/RCA cables run?


When you connect the HU center RCA to ground, you'd be initiating a ground loop into the system. I would expect to get noise. That means that power is leaving the ground point, traveling into the RCAs and then backwards through the internals and into the other Pre-outs, sending that on through the amp... You're completing a circuit that's putting power directly into the pre-outs. The amplifier is amplifying the 'sound' signal it's receiving...

Given that the IPOD directly into the amp had no noise, it sounds like a ground loop problem. I would see if you can find a different amp to wire in and see if you still have the problem. If you do, recheck all your grounds. If your grounds all check out ( <4 ohms to the neg terminal), see if you can borrow someone's HU. If your grounds check out, you have a bad internal amp/HU ground.

 

ok, found the problem - RCA wasnt being grounded through HU.
apprently common issue on Pioneer units. ground wire from HU chassis to RCA sheild wire has fixed.
for what it's worth, RCA's are ran down center console, behind driver seat and into drivers side boot.

so thats the biggest problem out of the way. what about my next problem: amp hiss.
doesnt change with engine speed and doesnt sound like interference, just like the gain is too high on the amp.
i've adjusted the gain from min to max, and it's all the way through range. it doesnt change with HU volume, and is apprent on all sources.

hiss is evident on both sides of the car and equal ammounts.

 

Hiss...like...white noise with the volume turned all the way down?

Or can you hear it over the speakers?

Or is it adding a lisp to the music?

 

ok......
HU is from 0 > 55 volume kotches.
0 = seems to mute the signal somehow
1 or higher = white noise. doesnt change loudness with HU volume control though.

volume of 1 = music inaudable, but white noise is deffinately there in the tweater range.

can hear it over the speakers till about level 15 so it's very noticable.

is this a case for sheilded wires, or is it something else causing it?

according to dad, white noise = noise down all frequencies. this seems quite specfically through the tweater units. best way i can decribe it is if the amp gain is set too high and HU volume is set high on a silent peice of audio.
zero difference with engine running.

pic of how it's wired up.

LFS & RFS = left/right Front Speaker; it's actually an Active Xover to midrange & tweater.
theres also a ground from the HU, to the amp earth point aswell, which isnt drawn in, in that pic

 

Double check your grounds, make sure that you're as close to 0ohms between the neg battery terminal and the amp and HU grounding point as possible.

I have the same white noise and know it's most likely a result of 4ohms diff between in-cabin grounding and the battery neg terminal. One of these days I'll quit being lazy and ground the interior to the neg terminal... (I'm actually a bit wary of doing this since I don't know if it will affect the computer/wiring harness at all)

 

ok, just just to clarify:

noise (like hiss) = a bad ground; amp&HU at the same ground point
interference (alt whine) = ground loop; amp&HU at different ground points?

i'll recheck the ground

thanks again neut!

 

Something like that.

Both are ground loops. One is a loop between the neg terminal and the ground point. The other is a loop between the ground points of each component.

Both can have either white noise or a whine...

I just know from my own experience that it's likely to be the ground loop between the battery and ground points. lol