Guys,
My newly-acquired 987 Cayman is causing me grief at the moment. The standard radio was terrible so I've installed a Pioneer double-din head unit in the dashboard and an older 4-channel amplifier in the front boot. Head unit is new, amp is old but known to be good. I'm running it active - i.e. with two channels on the amp to the mid range speakers in the doors and two to the tweeters in the dash. I've run the RCA cables and speaker cables through the bulkhead in front of the passengers and then again through the bulkhead beyond the battery into the front boot to connect to the amp.
I am having the most enormous problem with interference from the engine; there is a whine whenever the engine is started. And it's most annoying. I've done or observed the following:
- Good amp and HU connections. HU now connected to it's own custom loom straight to the battery +ve and -ve terminals.
- No whine with RCA's disconnected. Whine occurs only when both sets of RCA's are connected
- Whine seems to be related to the position of the RCA's and I think there may be a source of interference in the footwell, somewhere near the centre console. I have come across reference to the power cable from the alternator behind the seats to the battery in the front of the car and this would be a possible culprit, although without dismantling extensively then I can't see where this cable runs.
Has anyone else installed an amplifier in the front boot and if so then where did you run the RCA cables?
Does anyone know about anything else which could be such a significant source of interference?
Failing that, where has anyone else mounted an amplifier and how have you routed the RCA cables? There are very very few points where you can pass cable through the bulkheads in the front of the car.
The car is right hand drive, should this be relevant.
Thanks for your help.
Oli.
Just a guess but it sounds like a ground loop picking up the alternator. I've never seen a sure fire solution for this. Make sure that all components are grounded. You could also try isolation transformers on the RCA's.
Also search the install threads in this forum. You're not the first to run into this.
Interference comes from having the RCA cable run near the power wire to the amp.
Make sure that your signal wires (RCA) are run on opposite sides of the car from your main power source wire.
I have installed many amps in various cars over the years and this is very common.
Don't let your RCA's even cross the path of your main power wire.
Les,
Thanks. It's either ground loop or RCA interference. I don't think it's ground loop as there is a single wire that goes from the HU case to the Earth connection for HU to the Battery negative terminal to the amp ground. Then again I don't seem to get the noise when I run a signal from an independent source (i.e. my 'phone) directly into the HU end of the RCA's, so I'm confused.
It seems that there are people who have run aftermarket amps in their frunks so it must be possible. Here's a thread that described almost exactly what I am trying to do:
https://www.planet-9.com/987-cayman-and-boxster-electronics/232137-amp-installation-help-please.html
I'm just struggling to move on from where I am.
Thanks again for your help.
I have to wonder if this is why Porsche uses fiber optic connections.
The phone test probably is your answer. Your ground set up sounds good. Maybe the signal ground isn't tied to the chassis. Maybe the connectors aren't perfectly impedance matched. Don't know, just a WAG. I recall seeing solutions others have found in install articles. Just try things. I've never seen a guaranteed fix.
It is worth keeping the RCA cables and power cables separated like RJD suggested. The pesky things will pick up noise.
It seems very likely to be a ground issue. Grounding issues go away when you use optical like Porsche does. When using RCA cables, it is important that the various boxes NOT be tied separately to chassis ground / battery neg or noise will be carried on the RCA cables. The chassis is hugely noisy, so by tying boxes to different chassis points, all that noise is conducted on the RCA cables. You must float the amp (no connection to chassis) and tie its ground directly to the head unit ground, not a separate run to the battery.
Guys,
I should probably provide an update on this problem as it is now solved. My diagnostics seemed illogical; I only had interference when the RCA's were connected to the HU and not when connected to another audio source ('phone), but also only seemed to get interference when both sets of RCA's were connected. Grounds were known to be good and I hooked up a trail wire to link all the ground points together, reasoning that this should prevent ground loops.
A friend suggested that I should try some new RCA cables - extra-shielded ones by Krystal Konceptz. And that solved the problem. (Well, it diminished to the point that I am not sure I can hear it any more and no-one else can, so I am happy). I still think that there is a big source of interference in the footwell area as if routed the cables carelessly then the problem was diminished but not eliminated; bringing them forward and away from the bulkhead itself helped in this respect.
So, thanks for your help. Should anyone else read this and try to put an amp in the front of their 987 then it's worth splashing out on expensive RCA's. Had I known this at the time I could have saved myself MANY hours!
