Interference and DIS gone.

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sharma

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Hi,

I have managed to locate a lead which has allowed me to have 2 amp pre outs from my Symphony head unit. The lead can be seen at:

http://www.caraudiodirect.co.uk/blaupunkt-preout-lead-p-79.html

Having fitted it my amp works fine. However i am getting interference. When i rev the car, the rev noise comes through the speakers. Why could this be and how do i stop it?

My stereo also said SAFE MODE at one stage. This would not allow me to do anything. I took the blaukpunkt adaptor out and plugged the original adaptor back in and it began to work fine. I have now put the blaupunkt adaptor back and SAFE MODE has not come up again. Is this something i should be worried about?

Thanks.
 
You need to ground the HU properly (Audi don't), there are plenty of earthing points behind the glovebox. Also check the ground on your amp as this is critical. Use a chunky 8 guage or thicker for the amp and keep it as short as possible. The SAFE mode is more than likely because you disconnected the perm live at some point and it couldn't get a CANBUS reading as you'd disconnected the CANBUS lead in order to connect the Blaupunkt adapter. I take it you have a black single piece connector not the multicoloured one (where you can slide off the old yellow connector and slide on the BLAU adapter).
 
If you have removed the one piece single plug (not the different coloured split plug) and replaced it with just the Blaupunkt adaptor you have also removed pin 7 – ‘Infotainment CAN-Bus – High’ which is the reason for safe mode and no DIS.

Interference could be a whole host of things but usually it’s a grounding problem.

Edited to add : Andy beat me to it :)
 
Yep i have to black single piece connector not the multicoloured one. I am planning on cutting the black connector. I know this is not advised but at least my multi function steering wheel and DIS will work. Also it can't do too much harm to cut the single black piece can it? When i come to sell the car i will still be able to put both back in.
 
I have just cut the large single black connector and have connected the piece back to the system. This has given me my DIS back and my multi-function steering now works. However the interferance is now comming through the speakers whenever the car is on (even if the symphony HU is switched off). This is very annoying. What is wrong?

The person who wired the car put the power cables and RCA's down the passenger side. I know they should really be down different sides, however i have tried a ground loop isolator from Maplin and this made no difference. Is a surpressor different to this and should i try that? What else can i try. Please help.

Thanks.
 
Your amp remote is still live with the radio switched on or off.
This is because he has either taken the feed from a switched ignition source rather than the radio itself or you have an Audi radio like mine that does not kill the amp remote after you switch the radio off.

I take it you fitted the ground loop isolator at the amp end not the headunit end?


Try these steps to isolate the problem.

Unplug your RCA plugs from your amp.

Do you still have noise?

If YES = make sure you amp is not touching the metal car body if the amp is not touching the car body and you still have noise try a Power Line Noise Filter on the amp power feed.(edited to add : assuming you ground is up to the job)

If NO = if there is no noise from the amp after unplugging the RCA from the amp reconnect them and unplug from the head unit.

Do you still have noise?

If YES = then the RCA cable is picking up the power feed, if a ground loop isolator does not work then you need to reroute or try a shielded pair of RCA cables (not much point you might as well reroute).

If NO = then the problem lies with the headunit itself
 
I have no noise when i unplug the RCA's from my amp. It only makes the noise when the red RCA lead is plugged in. When the other one is plugged in there is no sound. I will try and re-run the rca leads and see if it makes a difference. If not, what can i do about the head unit itself? Am i stuck with it or is there a way?

The sub also makes like a thud noise when the car is switched off (i.e when when power is not fed into the amp). If i can't sort it out i am just going to have to go back to the standard setup as this noise is terrible. However any more tips will be appreciated as i will not give up so easily.

Thanks.
 
Turn ON thump is a somewhat easy fix by delaying the remote turn on to the amp until the outputs of the head unit stabilize.

Turn OFF thump is harder, the thump occurs when the amplifier is still amplifying for the split second that the output circuitry (capacitor) of the headunit becomes unstable due to voltage drop from power down (common problem on Audi).

So make sure the amp is actually turning off at the same time as the head unit with no delay.

If it is then you need muting FET’s on the RCA inputs. You can make your own in a box with these fet’s that will have signal in and out and a remote trigger. I also believe these are made available pre fabricated.

Maplin sell the components maybe they also sell prefabricated as well.

This should solve your thump problem as long as long its not a faulty Amp discharging direct to the sub.
 
I removed my headunit and connected wire to one of the rca's and earthed it onto the headunit. This has cut down the interferance a lot. However there is very little interferance now. Well i can live with it now. Is it ok to do this or is it dangerous? And the very small amount of interferance, is it actually just supposed to be there? There is an electrical sort of buzz noise which comes through the speakers when the car is switched on and then when the key is pull out. Is this normal?
 
audi upgrades
Yes its perfectly ok to do this but I would do it to both rca’s .(This is actually a known fix)

Also some people run an additional ground wire to the head unit chassis, the standard Audi one is not that good and people have reported some improvement once done.

No there should be no buzz,
Is the buzz present with the RCA’s completely disconnected from the head unit but still connected to the amp ?
 
Connect a chunky earth lead to the chassis of the HU.
Burn a CD with silence on it, play it on the HU, whack the volume up with the engine running and try different earthing points behind the glovebox until the noise disappears.
The screen/signal connection to the HU for the RCA's is totally exposed at the point it plugs into the HU which is closest to the engine. No other system uses this mickey mouse pre-out connector, RCA's should be completely shrouded to prevent the low level signal picking up alternator whine. So you need to ensure both the HU and the amp have a really good ground.
I run a Blaupunkt DAB HU in my B6 which uses the same connection. I have no interference at all. This is with an Alpine amp and to be honest the quality of the amp can have a lot to do with it. I only use Alpine V12's on my stealth sub installs for this very reason, as the amp has to feed both the sub and the rear speakers. When using inferior amps I have sometimes had interference issues, never with Alpines. Might be worth trying a different amp, just to see. What amp are you using?
 
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