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Fitting an aftermarket Sony Head unit!

iggy2202 Jan 3, 2007

  1. iggy2202

    iggy2202 iggy

    Hi went out and bought a Sony CD/MP3 headunit today but unsure if I can plug it straight in? Ive currently got the standard concert tape player (a3 1,8 se 1998). went to Halfords and got the spacers they told me I may need a PC9-401 to connect it at the rear of the unit. Later I went to another spares place and they told me I would be wasting my money getting one. Is this true? will it just plug in? what happens to the audi amp and sub?

    any help would be great!
  2. joost

    joost Active Member

    I didn't have any problems with mine but that's in an A4 without amp/sub. I just had to swap the permanent and switched lives round on the wiring loom that came with the head unit. TBH, AndyMac's your man - what he doesn't know about Audi ICE and amp/sub compatibility ain't worth knowing!
  3. ak_quattro454

    ak_quattro454 Member

    have you got a bose system in your car?? or do audi have a built in amp for the standard HU as well.
    If your car has got a built in amp you are definately going to need some kind of adaptor to make your sony headunit work with the audi amp, unless you wanna take out the amp completely.

    Anyway i had a similar problem, when i first changed my bose HU to a alpine HU.

    This is explained in more detail in this thread i started when i was after some help...........
  4. AndyMac

    AndyMac Moderator Staff Member Moderator

    As Joost says you'll need to swap the perm & ignition on lives as Audi wire them back2front on the black ISO connector.
    The front speakers will just plug straight in as they're on a standard ISO speaker connector.
    The only problem is providing a feed to the rear/sub amp.
    There are 2 adapters available:
    1. RCA input (PC9-401) - takes the rear RCA's from the Sony and allows them to plug into the Audi rear/sub amp loom
    2. Speaker input (PC9-404) - takes the rear speaker output from the Sony, converts it down to a pre-out level and allows it to plug into the Audi loom.
    There are issues with both
    1. Using the RCA method will give you the best sound, but will very likely cause a really annoying popping sound through the rear speakers whenever you turn the HU on/off or select a different track on a CD or turn the volume down to zero etc etc. This is normal, and the only way round it is to put tiny capacitors inline with the pre-out feed to the rear amp.
    2. No popping but the sound quality to the rears will be compromised slightly as the adapter uses a line out converter to take the 50w output from the new HU back down to a 1-4v pre-out level which is then fed to the puny 20w rear amp inside the sub. Not a huge issue in itself, but something to be aware of.
    With either "solution" you'll have a huge mismatch between the 50w from the HU driving the fronts and the 20w driving the rears & 50w sub, so you'll have to fade to rear to get it balanced.
    Ideally you need to ditch the Audi rear/sub setup & replace the sub with something that works properly, but its more money.
    As a compromise I'd rewire the rear speakers back to the HU so all speakers are running off the Sony, and then if the HU has a sub pre-out connect that via the RCA adapter to the Audi rear/sub loom. Jack up the sub level to max to get some sort of bass back in the car to match the higher output going to the other speakers.
    Or £300 will get you a stealth sub enclosure, JL Audio sub and amp which will transform the sound, be completely hidden and work properly.
    You'll also need an antenna amp for FM reception:

    Not the answers you were looking for unfortunately.
  5. iggy2202

    iggy2202 iggy

    thanks for the advice guys!

    I dont have the Bose system so now I am unsure if I have an amp! in the cubby hole on the left hand side of the boot there is a audi sub speaker. I thought that in that black box there was a small amp too! the model is 1998 a3 1.8 S.E dont know if that explains anything!
  6. Tooks

    Tooks Active Member

    Hi, you should have an amp/rear sub.

    I've just fitted a Becker head unit to my car, and I've used the PC9-401. Fortunately, I don't suffer from the popping problem Andymac describes, but mine's a canbus car so I don't know if that makes any difference. The adaptors can be picked up quite cheap online, and I think they are worth it if only so that any swapping around of wires/splicing etc can be done on the adaptor harness and not on your car loom. I had to pick up an illumination wire and speed sensor wire for the Gala and satnav function on my head unit, and the adaptor meant I could mess up it's connector rather than my car one.

    I second that you'll still be left with the mediocre speakers and rubbish rear amplification, but then you knew that didn't you?! ;o)

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