Here's the deal:
Alpine 9835 h/u, 4 volt preouts. Power connected straight to the battery to cope with the big internal amp - that is basically useless in my application because I will be powering everything with amps.

Currently two Pioneer two-ways up front running off a Pioneer two channel amp. Previously I had a JVC KDLH-2000 head unit installed the same way, except for the power going straight to the battery.

I can hear engine noise from my front left speaker when I turn the car on, and the high-pitched sound gets 'faster' when I accellerate. I can also hear when a CD is being loaded and fast-forwarded etc. There is also noise when the engine is off, this is more like a gentle hum - again, only from the one speaker.

I moved my earth cable from near the handbrake to the same spot the ECU gets its earth so I am positive it's not that, and I am pretty sure it wouldn't be my brand new head unit.

Help me!

PS: I shouldn't have a need for added noise-suppressors as I never had this noise, and the unit has a very high s/n and 4v preouts.

try swapping the RCA inputs to the front amp around, it may be a faulty shield in the lead. could also be a faulty connection on the PCB inside the amp.

Thanks for your response joolz, I thought you may have been onto something there as one of my RCAs looks like it's scored a bit of damage But it wasn't so next is changing the amp or power source.

highly unlikely changing the power sourse will fix it. does it do it with both line inputs unplugged. if it stops buzzing its not the amp. something before the amp like leads or the actual HU.

Short circuit the appropriate amplifier input at the amplifier input (after disconnecting it from the head unit of course!). Does it go away? If so, good, amp is fine. Get another lead and run it between the head unit and the amp. If that's fixed it, good, go and buy a replacement lead. If not, need to do further exploring.

Although you rightly state that the SNR on a 4V line is high, its still only 12dB (20log(4/1) ) more than a 1V line, and in a car environment coupled noise levels will easily surpass that.

The ideal cable between a head unit and amp is a shielded balanced twisted pair.

HU end
TP+ -> Output.
TP- -> Signal ground
Shield -> Signal ground

Amp end
TP+ -> Input
TP- -> Signal ground
Shield -> No connection.

This configuration will ensure ZERO shield current, and ensure all return current goes back to the head unit via the desired route.

Have fun,
Dang.

I had my amps banging round in the boot and the sub box snapped the shielding on one of the RCA's. There was a god awful whining noise that went in time with the engine. Swapped the RCA's on the amp around to find which one was faulty,replaced it and bingo, sounds beaut. I also have my front drivers speaker line running right up against two power cables and dont find it to interfere with the sound. Now i have my amps screwed down on a bit of mdf till i get my boot setup sorted

i thought i had that problem but i'm pretty sure in my case it's the a/c since it only ever happens when it's on.

I ended up rewiring my power, earth etc only to find it was my bloody RCAs I am pretty p****d as they cost me 60 a side and I managed to put the tiniest of holes in it.

Cheers guys