Aftermarket head unit wiring

Horlix66

Registered User
I have fitted a new Sony double din head unit into my 2004 a3 (originally symphony double din/bose) and everything works pretty well (well the rear sub seems a bit muffled/weak but I'm not that bothered)

However something somewhere is draining my battery - it was totally flat this morning :-(

I have wired it red to red. Yellow to yellow. Blue to blue. And the radio antenna powers from the red.

Any ideas
 

NHN

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Clearly something connected to a permanent live is killing it, so charge the battery, then disconnect the antenna, sometimes these drain the battery & you may need ignition switched for a connected device, without knowing your head unit or wiring looms used, even if most are often similarly wired, it's best to know specifically what's been used/fitted before adding any advice.
 

Horlix66

Registered User
Thx NMN

The head unit is a Sony wx gt-90bt and i ebayed a connects2 harness as pictured..

I have wired the bose amp (a blue wire) to another blue wire. Having researched a bit there is a blue/white stripe wire in the bundle from the HU that doesn't connect anywhere - is it possible the amp should be connected onto that one?
 

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Horlix66

Registered User
Ok so this is what I have coming out the dash board - there is nothing that connects to the thin brown wire
 

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Horlix66

Registered User
And this what I have done wiring wise

Blue is amp power red is switched power

Yellow (constant power) and red should go together as my ignition barrel doesn't have ACC position (or so it states in the instruction manual) does that sound correct???

Waiting to see if I get a flat battery again or not
 

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leshkin

Hold my beer...
VCDS Map User
And this what I have done wiring wise

Blue is amp power red is switched power

Yellow (constant power) and red should go together as my ignition barrel doesn't have ACC position (or so it states in the instruction manual) does that sound correct???

Waiting to see if I get a flat battery again or not

Blue does not supply power to the amp or anything else for that matter (it may power the little radio aerial amp adapters), it is primarily used to tell the remote amp when to power up and when to switch off, based on the power state of the HU. The amp will have it's own power supply. If you plug the blue wire to the red wire, you have signaled to the amp to stay constantly on, which would drain your battery as you describe.

On any of the harnesses, the blue wire signal direction is from the HU to whatever device that needs to know when the HU is powered-up. With that in mind, the blue wires for the amp and radio signal adapter need to be connected to the blue wire coming from the HU.
 

Horlix66

Registered User
Thx leshkin

I have got the wiring figured out - well, no flat battery yet anyway!!! I had the amp connected to the constant power which obviously was going to be a problem,

All I am suffering from now is the low volume level whine - any advice on getting rid of that would be appreciated

Thx
 

leshkin

Hold my beer...
VCDS Map User
OK, the whine is quite common when using RCA leads to connect the HU to stock amp - not 100% sure on the technical reasons for that (something to do with bad ground for HU or amp), but it can be overcome with a couple of options:
  • RCA ground loop isolator - cheap grenade-shaped thing, which plugs in-line between HU RCA output and amp.
    • Pros:
      • Easy to fit
      • Removes a loud speaker pop noise that sometimes happens when amp is powered up with aftermarket HUs
      • Removes the whine
    • Cons:
      • Due to how it works it tends to clip the frequency range of the audio signal, so you rears and amp will not have much bass going to them
      • Quite bulky and can be a pain to fit behind the HU in the dash
      • Does not completely remove the amp hiss
    • Linky: Search ebay for "RCA Ground Loop isolator", cost between 5 and 20 quid
  • RCA noise filter/Suppressor - slightly more expensive at 20, but seems to work well with Audi/BOSE amps
    • Pros:
      • Small and fits easily in the dash
      • Works for front and rear RCA feeds
      • Removes the hissing from the rears and whine that can sometimes be heard from the speakers at low volume
      • Does not seem to clip the audio signal frequency as much, so more bass from rear/sub
    • Cons:
      • Harder to install as it needs a ground connection (black wire) as well as power (blue - can be connected to amp remote wire from HU)
      • Slight speaker pop at power-on/off can be heard sometimes, but it's minimal
    • Linky: http://www.ebay.co.uk/itm/252307253937?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
I just switched from the ground loop isolator to the filter this week and so far have been pretty happy with it.

As far as low volume from rears goes then it's a very common issue and the best way to get rid of this is to fade to back on the HU settings until you get the desired sound stage. The only way to fix this is to bypass all of the stock Audi/Bose crud and install a proper set of speakers/amps/sub, which can be quite costly depending on your tastes.
 
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Horlix66

Registered User
Brilliant info thx leshkin

I have a GLI already, and whilst it is an improvement, its still not perfect. Has the suppressor removed the whine 100% of the time for you?

Plz do let me know how you get on with it after a few weeks use... if it solves the problem it's gotta be worth 20 bucks

Thx again
 

Horlix66

Registered User
For the record, I fitted the suppressor as mentioned above by leshkin and it works brilliantly - stopped all my low volume buzzing and ground noise. Much better than the ground loop isolator

Worth £20 all day long
 
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