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Howto: Retain factory amp (MOST fibre optic) when changing head unit

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This is for my 2004 986 with active amp (MOST)

So I've just upgraded my CDR 23 to a (Chinese EONON) double din Android unit. I wanted to keep it simple so retain the factory amplifier and speakers for now.

The factory system uses the MOST fibre optic to transfer audio so there are no ISO connections from the factory head unit for audio.

Now there are a number of videos on YOUTUBE etc of how to modify the radio frame and fit a unit but I'll describe what i did here and if anyone wants any info or pictures I'll post them up or send them via email.

First thing is you will need a fibre optic to analogue converter box, this sort of thing, although shown for Merc its exactly the same, the one below is listed for Porsche but includes P Tax :)

https://www.ebay.co.uk/itm/Fibre-Optic-Adaptor-Box-Amp-Amplifier-Decoder-for-Mercedes-Benz-ML-GL-R-Class/153514798436?hash=item23be31ed64:g:qNoAAOSwiZddSoYC

https://www.ebay.co.uk/itm/Fibre-Optic-Amp-MOST-Decoder-Adaptor-For-Porsche-Boxster-Cayman-987-2005-2012/182678779836?hash=item2a8880f7bc:g:wdsAAOSwOzZZcdmC

 

287386286_mostbox.jpg.9ebe210f5486e774d64acb95e5f0b24f.jpg

 

 

 

So you plug the MOST connection that goes in the factory head unit into the converter. Wiring wise B+ is permanent live, GRND is , well ground ( -ve) and ACC goes to the amp wire on the new stereo.

Connect the FRONT RCA out from the new stereo to the RCA leads on the converter. If you use the rear output you will not be able to here your phone on bluetooth or Carplay, ask me how i found that out ........

 

 

https://www.ebay.co.uk/itm/Add-A-Circuit-Fuse-Tap-Piggy-Back-Standard-Blade-Fuse-Holder-10A-Blade-Fuse-GL-/302847053113?_trksid=p2385738.m4383.l4275.c10

541450348_90degreepiggybackfuse.jpg.e50c79963d3b36105c0f931a0d29e3f5.jpg

You will need to fit a switched live 12v +ve for the new stereo. I used a 90 degree tailed piggy back fuse to slot E1 as the head unit trigger only needs up to 5 amps and should have an in line fuse anyway. I managed to get a connector for the iso socket and wired it in. You can feed from any switched fuse and do not worry about the amperage as its all 12v draw and the twoo fuses are on separate contacts within the piggy back.

 

 

 

 

 

627805826_powerplug(A)1.jpg.fde6dfce1c93eedc36dc66a8a235fd25.jpg

This is the factory ISO connector with the switched 12v +ve fitted. the wires above are: large Red/Black perm 12v +ve, large brown Earth (-ve), white (actually looks greyish in the picture) next to the switched live < this wire connects to the new stereo antenna feed. The Blue/Black and Pink/Grey are phone mute and vehicle speed wires which aren't used on my car as its stereo was bog basic .

 

 

 

 

 

 

655461907_yellowplugwiring1.thumb.jpg.b074c43ffc2db487705bce5d22f7b10d.jpg

 

The yellow mini ISO which was in my factory unit is unused after market so leave it unplugged

 

 

 

 

 

 

 

My new head unit has GPS, wi-fi and DAB+ , so i fitted the GPS receiver under the front plastic scuttle mounted on compound foam and fed the lead through the big rubber grommet the factory wiring uses. The wifi antenna is fitted to the A-pillar near where I have mounted the sceen DAB aerial. I also fitted one of the usb cables into a blank dash switch to run my phone/CarPlay. I routed an external mic for the phone functions into the dash pod where the factory mic blank is.

Other stuff you will need: Double DIN fascia fitting kit,   something like this 814186978_doubledinkit.jpg.24bc4c0e226821d54474717afaedbbb8.jpg   

insulation tape, soldering iron pliers, pry tools, some basic car electrics knowledge or understanding, multi meter, high pain threshold for all the sharp metal edges you'll find under the dash.

Stuff I learned doing this:

Chinese head units are just over double din size at the front screen body, meaning I had to do some re-modelling of the surround I bought (which wasn't the one pictured above unfortunately). Proper brands are the right size but much pricier.

Fitting stuff without instructions tests my patience. Porsche clips and plastic tabs are sturdier than most but can still be broken through ham fisted mingebaggery. Take your time , I did this over a couple of days during the Zombie apocalypse so was able to walk away when things had me ' a bit tense' 😠

There are hundreds of really sharp metal edges under the dashboard.

Anything after market is way better than the factory . I made the PORSCHE logo, proper Blue Peter effort !

(If anyone has a storage bin and wants to swap for the CD storage in the picture or sell let me know. It needs to be from that location not the lower one where I've relocated the HVAC controls to )

The result

298141423_Doubledinfitted1.thumb.jpg.a55cebb18c65bf6c1a55105776fff7ce.jpg

 

Thanks for looking.

 

 

 

 

Edited by Shazbot
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Excellent work 👍very impressed 

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Cheers ,always quite satisfying when you achieve something, no matter how small.

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Wow thanks so much, I have order a 10.1” offer was accepted at £195. Just wanted something bigger as dash is a bit boring, can’t wait till everything is here the I will fit it 

C1635EB3-20C4-4413-BF7D-5C290414F721.jpeg

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Can I ask what fascia kit you used and do you have a link to it.  I have fitted the kit you have shown and the stereo i bought to fit it is not great to be fair.  From that kit I also have the compartment spare if you are still looking for one.

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