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Hi, I'm new on here and this is my first post. And I'm posting because I've put together an install in a 987 Cayman and can't get rid of a terrible alternator whine. How terrible? Terrible such as to make the system unusable - it's loud. This may be a long post with quite a lot of detail but I have reached the end of my understanding and don't know what to do next.

My system is as follows:

- Pioneer FH-X840DAB double-din HU (bought new recently)
- Old Directed 4200 4-channel amp, run actively from the HU
- Focal 16.5cm speakers, standard tweeters

The earth wiring is thus:

- Amp: Big earth wire to nearby bit of bodywork.
- Thin wire from amp earth terminal to battery negative terminal
- Thin wire from battery negative terminal to HU earth
- Thin (very short) wire from HU earth to HU case

The live (positive) wiring is like this:

- Amp: Big live cable to battery +ve (with fuse, natch)
- Thinner wire from battery +ve to HU constant feed
- Thinner wire from battery +ve to relay, which is controlled by the main loom ignition live. When the ignition is live this closes the relay which connects the battery +ve to the HU ignition live feed

There are two sets of RCA's from the HU to the amp and it all sounds lovely when the engine is not running. However when you turn the engine on there is a HUGE whine when you use the starter motor and then a slightly less loud whine from the engine. It is related to engine revs (higher frequency when the engine is revved). And I can't get rid of the whine.

The power feeds are simple and I believe that the earths are all good (all run back to the battery). The cable to the amp is heavy and the amp is earthed to a solid point very close to it. I therefore assume it is interference in the RCA leads. However the whine is not constant in it's properties. I've observed the following;

- Either set of RCA's on their own are fine. The whine occurs when you connect the second set of RCA's
- There is no whine when both sets of RCA's are disconnected
- The whine changes when the position of the RCA's relative to each other changes. It seems that the whine is lesser when they are held apart from each other (hence routing them via different routes)
- Trying a different HU (single-din Pioneer) produces exactly the same whine. I therefore don't think the HU is at fault.
- Playing around with the routing of the RCA's in the driver's footwell suggests that there is a source of RF interference there as I can almost make the whine go away if I hold the RCA's in a tortuous place away from the pedals (which would make the car impossible to drive). I am almost wondering whether there is something big and chunky there which is causing problems - perhaps a big cable from the alternator (in the back of the car) to the battery (in the front of the car). This would possibly explain the problems, but given the layout of the car and the fact that the bulkhead in front of the driver has very very few places to pass an RCA cable through I don't know where else they could be run.

If anyone has any suggestions as to what could be wrong or (better!) any experience of building ICE into a 987 Boxster or Cayman and putting the amp in the front boot then I'd be really grateful to hear from you. I am perplexed by what is going on here and don't know what to do next. One option is to assume it is RCA interference and buy some really expensive RCA leads (the current ones are double-shielded but only mid-range). The other option is to abandon the install altogether and move the amp, possibly to a position under the passenger seat. However I feel that I'd rather make the current setup work if I can as moving the amp will be a lot of work (and this has taken a VAST amount of time already.)

All help and suggestions welcomed. if it's relevant then the car is right hand drive (I'm in the UK).

Thanks in advance.
 

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Welcome to the world of Porsche lol
I’m a retired/disabled master Porsche tech
Under each side of the cars floor boards is a peace of wood where you would put your feet at. Under them they have some of the many ( 23 plus) ecu’s installed there. And on your car it uses 6v 12v on both the +&- sides
And they all make tons of noise.
Your best bet is to use the type of balance cables that are used for xlr cables
On the end of your HU you use two grounds
And at the amps leave the outer shield wire unhooked.
Where do you have the amps I stalled at?
You could also run the rca cables underneath on the outside all the way to were the amps are. That way your staying away from all the Barry directional wiring that they use in the Porsches.

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with The radio in your hand, use a piece of wire to ground the rca to the heat sink of the radio. Make sure you ground it to the heat sink the report back
 

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Welcome to the world of Porsche lol
I’m a retired/disabled master Porsche tech
Under each side of the cars floor boards is a peace of wood where you would put your feet at. Under them they have some of the many ( 23 plus) ecu’s installed there. And on your car it uses 6v 12v on both the +&- sides
And they all make tons of noise.
Your best bet is to use the type of balance cables that are used for xlr cables
On the end of your HU you use two grounds
And at the amps leave the outer shield wire unhooked.
Where do you have the amps I stalled at?
You could also run the rca cables underneath on the outside all the way to were the amps are. That way your staying away from all the Barry directional wiring that they use in the Porsches.

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I don't know of any head unit that offers balanced outputs. I think his best bet is to go digital. Get a headunit with optical output like the Clarion NX807. Their support sucks but at least it mostly works. He would then need a DSP that accepts optical output.

The cheaper alternative is to get some high quality RCA cables and see if that kills the noise. I would try KnuKonceptz krystal RCA cables.
 

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I’m not saying use balance cables completely
I’m saying use the same balanced cable and use rca and only hook up the shield on one end. The end at the head unit

IMG_4766.JPG


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I’m not saying use balance cables completely
I’m saying use the same balanced cable and use rca and only hook up the shield on one end. The end at the head unit

View attachment 248681


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Ahh i see. That may work.


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i have had a whine on all my porsche, zapco makes a noise filter, its a current piece and it works like a champ
 

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Porsche is Notorious for putting out ac voltage ( no more then 1.35acv is ok ) from the alternator and still putting out 14plus dc voltage


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Discussion Starter #9
Guys,

Thanks very much for the replies to this question. Carlthess40, thanks also for the PM. I'm in the UK so your offer of making the cables for me is very kind but importing them from the US would be tricky (I've been stung HARD by import duties before).

The amp (singular) is installed in the front trunk of the car. To get cables to there from the head unit involves passing through two firewalls; the one from the passenger compartment to the battery compartment and then from the battery compartment to the front trunk. In this picture the battery lives underneath the panel marked 'Porsche' in the red box and the amp is on the vertical carpeted section. There is a bulkhead both in front of the battery (underneath the seal around the trunk storage space) and behind the battery (underneath the windscreen). Getting cables through both of these bulkheads is tricky and the options are limited.



Mullings - thanks for the test of putting an earthed cable on the HU heat sink. I'll try it and let you know what the result is. The case of the HU is connected to the HU ground connection which is then connected to the battery earth terminal and then the amp earth terminal, all with one wire. I'd hope that this means no ground loops, which is what some people have suggested it could be.

Tonynca, optical is appealing as it's interference-free but the Pioneer unit I have was bought for this car and I don't have the budget necessary for the sort of thing you are suggesting. If we really are in the world of RCA interference then some better RCA's are a good idea. Thanks for the recommendation of KnuKonceptz krystal RCA cables. I've googled them and they are surprisingly cheap! Ideally I need a 4m length and it seems that 2m is the readily-available size in the UK but I'll carry on hunting. Thanks again for this recommendation.

Carlthess40 - thanks for that picture of an XLR cable with RCA ends. This looks VERY promising. When you say "only hook up the shield at the head unit end" I presume you mean hooking up the other two connections (hot and cold) at both ends but only connecting the shield to the cold at the HU end? I have some XLR cable in my workshop and RCA ends are eacy to get hold of so this could be a great thing to try next!

Porsche - thanks for the recommendation of Zapco filters. Several people have suggested them. What do they do and how do they work? I have heard that they do nasty things to the sound quality - is this so?

Porsche notorious for noise? I had a similar problem in my old 944 which turned out to be a dodgy HU wiring loom, which is why the first thing I did with this car was to make a new HU loom and run it straight to the battery.

Thanks again everyone for your help. I'll keep this thread updated.
 

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the zapco is an inline filter for the rcas, whoever told you they effect the overall SQ is wrong, i have had to use them on 3-4 cars an all my cars have sounded very nice
 

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Using the mic cable or as most call them xlr cables
On the end were you would plug them into the head unit is were you would basically have two grounds or neg wires and one plus
So your using the shielding braid of the cable as one of the grounds and on the end that plugs into the amp, you don’t use the shield part of the cable. Make sure it’s not touching any of the other wires
One way I’ve run cables in a porche is to go under the headlamps. Very easy to pass the wire though the bulkhead rubber grommet for the headligh wire harness . Find some copper shielding that you could rap around the cables that are close to the headlights
Really important if you have HID lights
The ballast for the HID lights put out a ton of noise , good luck



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Discussion Starter #12
Guys,

An update on this: it was the RCA cables. changing them for some KnuKonceptz Krystal RCA cables (as recommended by Tonynca) almost entirely solved the problem; when first installed they were substantially better than the previous cables but I had to do some more work on the routing before they were entirely silent. There is still something down in the footwell which makes a load of electrical noise and I've had to keep them away from that area.

Thanks very much for your help - it is appreciated. Thanks particularly to Carlthess40 who showed a LOT of interest and was particularly helpful. I liked your instructions for home-made balanced cables and if I hadn't found such a good deal on the KnuKonceptz cables then I would have gone down that route.

I'm very happy that I now have a car whose radio can be listened to without a bad headache. I was despairing of ever achieving this!

Thanks again.
 

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Glad you fixed most of it. Cable matters.


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