Your advice please.

To set the scene:

I have an Alpine IDA-X100 HU and a 4 channel amp in the boot connected by RCA leads. The 4 channel amp currently only runs the 2 door speakers (Channels A&B).

When the HU connects to the AMP via A&B RCA's, everything is fine. When I connect the C&D RCA's on the amp to the rear RCA outputs on the HU I get a lot of electrical noise through the front speakers.

I've not connected speakers to the outputs (C&D) on the amp yet, I'm just getting the connections ready.

I suspected it may be due to noise bleeding into the RCA leads so chucked another RCA lead in down the other side of the car under the panels but whichever RCA I use, as soon as I connect C&D inputs to the amp, I get noise from the front speakers.

When I disconnect C&D the noise stops.

Any ideas?

The point of this exercise is to fit the roll bar mounted speakers but I haven't got very far with this yet due to this noise issue.

Help...

 

Which amp are you using? It might be some sort of setting on that.

PS IMO you'd be far better off by fitting some MY02+ doorcards and some proper component speakers, and then using the 4 channel amp to bi-amp/actively run those. You'll get more volume, better imaging and a clearer sound if you do that. Headreast speakers will give you more volume and a clear sound, but ruined imaging.

 

I can't remember the name of the Amp but it's set to 4 channel. I had the rear 2 channels bridged to power a sub last year but disconnected it when I took the sub out for the France trip. That's the 3 channel setting.

I don't remember getting the noise before when that set up was running.

I'm not a massive audiophile, I just wanted to make the most of what I already have and the roll bar speaker mounts were cheap.

It was just to get some sound higher up than just pointing the OE speaker points at my feet.

 

Have you tried connecting speakers to C&D and then the A&B RCAs to C&D, or any other combination?

 

No. Good point.

I'll give that a go now.

 

I had this same problem I'm my Subaru using a cheap fli branded amp. First time in 8 years I'd ever experienced anything like it. In the end nothing sorted it and I just disconnected the rear channels as they weren't essential.

If it's a cheap amp it could be an internal suppression problem

 

It'll be fine once you have some speakers connected to the rear channels (C&D) until then just leave the RCA's disconnected...

 

If using oem speakers, you might find they share a common negative line.
This is quite common on older factory systems in many manufacturers.

If not this, you may have an earth loop problem.
Try taking the amps ground AND the head unit earth stud ground back to one common star point, maybe at the boot floor.
Having two earths at different points can cause an imbalance.

I still suspect the oem wiring isnt liked by the amp - try wiring yourself and go direct if you havent already.

Steve

 

Thanks.

They're upgraded door speakers (albeit 3 way) with wires fed from the amp in the boot.

The problem only occurs when I connect the rear RCA leads.

I'll try what madfish suggests when my speakers for the roll bar brackets arrive and until then I'll give lovegroova's suggestion a try in the morning to rule out that.

Cheers all.

 

Ground loops or poor ground at HU or AMP.
Also does the noise change with RPM?
If so it it may be noise injection from running RCA's to close to cars signal and power loom.
Correct grounding & shielding will help but best to move them away.
I had the same problem on my first S and solved it with one really good earth on the upper rear cross bar bolt and RCA's down the centre console.

ETA - avoid using the OEM loom for any of your ICE upgrade