Questions on aftermarket headunit install on car with Bose MOST

I have a 2004 with the dreaded Bose MOST system, complete with factory amp and single DIN CDR-23. For now I plan to swap out the CDR-23 with another single-DIN head unit (McIntosh MX406), with plans to eventually replace amp and speakers when my wife's not paying attention. I have ordered a longate MOST converter box from aliexpress: https://www.aliexpress.com/item/RCA-...708723316.html So I've been trying to sort out the rest of what I'll need. I have ordered a Metra 70-1787 Metra 70-1787 adapter, as well as a Metra 40-EU10 Metra 40-EU10 antenna adapter, and I also have the Becker autosound 5001.524 adapter that I ordered a while back from ebay with plans to tap into the phone plug to give me a switched-power USB power plug somewhere in the car (maybe in the batwing?). So on to the questions: 1) I see that the CAI instructions recommend running a wire directly to the ignition switch on the 03+ models for switched power. Does this mean that location on the black plug on the Metra harness for switched power doesn't work? Or is just for the functionality where when you turn the car off but still have the key in, the radio is still going? I'm pretty sure I don't care about that, as long as the radio cuts off when the car is off and my battery doesn't drain. 2) followup to 1: assuming the switched power can't be found in the black plug, is there anything wrong with tapping accessory from the becker phone cable? 3) also a followup to 1: if switched power isn't available directly from the harness, how does the factory radio turn on and off? Thanks in advance!

Sorry I cant be more help but I know for my unit to work (same MOST system) I had to run the ignition wire from somewhere in the center console to the radio. I remember because I was trying to test the unit before getting too far ahead and the unit would not turn on at all until it had both the ignition and constant 12v to the system. This was on a double din unit though so it could have been specific for my deck. Not sure. Good luck and it was actually fairly easy. Hardest part for me was relocating the hvac to the bottom (issue was fishing the wiring harness down.. Spend 20-30 mins 3 or 4 times.. Took breaks.. Last time I went out and fished it through in 2 mins).. You wont have to worry about this going single din though.

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thanks! No need for me to relocate trim bits because single din, and if I was going double din I'd order the Porsche OEM parts which makes that easy (if expensive) I'll post results here when I'm done. still waiting on customs on the Longate.

Yeah mine took quite some time to get here.. I did have all the OEM porsche parts which didn't make it too hard. The only issue was actually fishing the wiring for the hvac down to the bottom and like I said one time I got it relocated in 10 mins after spending over an hour multiple times trying to get it down. Good luck.. Also word of advice (im sure you will do this anyways). But when wiring the fiber-RCA converter splice on the aftermarket radio side of the harness. Makes it very easy and leaves the car factory.

Nice HU choice! Wish i could help, interested to hear how this goes. Just recently acquired my car and it has a pretty serious aftermarket system that I haven't had time to dive into yet. I sold/installed consumer audio gear back in college, but haven't touched it in years. My car also has the MOST system, but the PO installed Zapco DSP amps that I think somehow integrate into the oem fiber optics. There's an aftermarket HU but no RCA's running to the amps, not line level either. It's some kind of proprietary "symbalink" cables that i need to read up on. Let me know if you get stuck, I'm local.

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Save the trouble trying to tap into the ignition switch and connect the 12V switch power to your "porsche phone" accessory plug, that is located to the left of your radio. (see picture). RED/GREEN = 12V constant GREEN/BLACK = 12V switched BROWN = ground

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This is definitely solid advice, I don't plan to cut anything on the factory harness. This sounds like a really cool install. Please post details once you dig in! Zapco is on the short list of amps I'm considering for the next phase. I'd love to see pics! Also, are you a PCA member? I am, but I've yet to go to a meeting (I suck). Thanks for the response! I even have the overpriced pigtail from Becker's ebay store that plugs into the phone connector, so I won't even have to cut anything. I also ordered one of these: https://www.newegg.com/Product/Produ...00Z-0132-00001 and I'm thinking I'll cut a hole in the back of the cubby and run that through, as well as one of these: http://www.rennline.com/ExactFit-Mag...nfo/PM01%2E08/ With any luck, I should hopefully get to install it this weekend!

Most of what you are trying to sort through can be found here... https://rennlist.com/forums/996-foru...ory-amp-8.html

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I read that thread, a lot of what I knew to order came from there. Got it installed this weekend with the help of a friend... or, more accurately, I kept the beer glasses full and provided moral support while he did most of the work I've heard other people mention how much better the factory system sounds once the Becker radio is evicted... I am surprised that I now agree with them. The longate china box sounds pretty damn good, and that amp and speaker combo is properly decent. I still plan to eventually replace the rest of it, but at least in the mean time I have a proper aux in. Here's a bad photo (sorry for the mess still in the floor)

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Great write up and glad to hear you the headunit alone made a difference. Need to tackle this in my 02.

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Your 02 will be much more straightforward, no fiber optic to deal with. by the way, love your 964(?)

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Thanks! Its an 87 (pre-964) -cheers

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Ahh, okay. I got confused since the 964 had the 3.6 and the G50 transmission. So what's the story on the engine on yours?

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Its a mostly stock 3.6L out of 1995 993. Plan is to run it like this for a few seasons and then build the motor, perhaps 4.0L, we'll see.

Not trying to bring back this dead thread, but it seems the most detailed of anything I've found after days of researching. Looking to simply do one thing, add Bluetooth to a 987 with Bose. Which would best accomplish this? Longate - https://tinyurl.com/ybjotnrz CAI - https://cai-store.com/collections/al...ant=3737574725 AVIN - https://avinusa.com/most-fiber-optic...e-cayenne.html iSimple - Amazon Amazon Dension - https://tinyurl.com/y944mx88

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Is this Metra 70-1787 Metra 70-1787 adapter required? My assumption was everything is taken care by the MOST box for sound and I can leave the small yellow plug not connected. What does this adapter do?

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The harness is required for several reasons, one is to provide amp turn-on signal for the bose amplifier and the antenna booster (iirc, been a while). it also provides dimming. The longate box just gives you rca inputs.

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So the blue/white wire from HU harness needs to be connected to metra 1787 blue wire / white and red wire from MOST box can be connected directly to the switched power (coming from ignition)? Because I am hearing a pop sound when I turn off the key and radio powers off.

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That sounds correct, longate red to switched power and yellow to constant power, HU blue/white to metra blue/white. Other than the pop sound when you power it off, is it otherwise working? Where did you source your switched and constant power from?

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Current wiring without metra 1787 and yellow plug connected together Yes it is working fine other than pop sound. I still have "whine when RPM goes up", but I believe that can be fixed with proper grounding. I followed CAI instructions and ran the red wire from ignition switch. Constant is coming from factory harness.

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Oh! I misunderstood earlier. You don't need to plug in the yellow plug to the Metra harness. I thought you were asking if the Metra harness was needed period, which you generally need to use if you don't want to cut up the factory harness. And yeah, the pops and rpm noise definitely sound like they might be ground related. Also, have you tested to make sure constant is actually present at the factory harness? I remember having to source it from the phone plug, but again, that was almost a year ago so my memory might be faulty. Do you have a meter to test?

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Yes I have used a test light and checked that constant is present. I will disconnect the MOST box ground from harness and try to find a different source and see if the issue goes away.

The popping sound can be eliminated with a ground loop gadget. $10 on amazon or ebay. for ground, connect to one of the bolts at the bottom of the stack.

So I really got tired of listening to my pandora through a bluetooth FM modulator so I ordered a Continental H/U, harness an LOC from BergvilleFX. After installing the LOC box didn't work but luckily I accidentally ordered an additional one from Aliexpress. So everything works nicely and looks the way I want it to, but I am getting the RPM whine through the speakers. An audio guy told me to change it to RCA hook ups and hook up a noise canceler to it but I have a feeling that I can cut into a different wire or something it will go away. With this harness, any idea of what I need to do? Harness from BergvillFX

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The Continental units don't offer RCA pre-amp outputs. It's been one of the unfortunate drawbacks. That's why they offer a speaker-to-line conversion adapter for Porsche owners. If you're getting alternator hum, then more than likely there is a ground loop occurring.

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I am trying to figure what I need to do with this harness and h/u to get rid of the alternator hum. I will say this, the BergvillFX people have been very helpful and communicative along the way. I am wondering if they sent me a new harness if that would fix it. Or I am wondering if I should re-route the ground wire...

Did the alternator hum occur with the OEM radio setup? In other, has it just begun since you installed the new Continental radio and speaker-to-line harness?

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No, it worked perfectly before.

i'm not convinced that it's a grounding issue or an alternator hum. ground loop typically result in a noise thats 50-60 hz. Download any frequency app on your phone and you can diagnose whether it's really ground loop. as for alternator hum, the factory bose amp is wired to constant power, meaning if you power the optical converter to constant power, or just another battery, you can drive the amp without turning on the car. doing that can help you eliminate a couple more sources of that noise. lastly, if what you are trying to achieve is just some bluetooth connectivity, and not a double din touchscreen hu, the best option may be to undo some of this work, pop the factory cdr23 back with one of those bluetooth kits that go through the radio antennae.