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Discussion Starter · #1 ·
Hi all,

I have an interesting problem to pose to the techies amongst you.

I have just managed to get my dream car and now need to integrate my phone without paying the huge sums being asked for by the car manufacturers and some aftermarket electronic suppliers (car ICE specialists too). My phone is currently a Samsung Galaxy Note 3 and the car (Aston Martin DB9 2005 with no Bluetooth and the stock base Linn 260W audio system) has a MOST optical audio and satnav systems. My earliest idea was to find someone with the necessary skills and knowledge to wire in a connection into the head unit itself to replace either the radio or cd input which is not something I really wanted to do as it limits function. Plus I suspect that the output might have to come from the headphone output rather than the USB port which raises questions about the right voltage range going into the head unit circuitry. Please note, I'm NOT looking for a hands free solution as I never use the phone when I'm driving.

So now I'm after 3 distinct, yet simultaneous, solutions, which are : -

A/ power supply to the phone
B/ HDMI or RCA output to a dash mounted 5 inch lcd screen for satnav purposes
C/ audio output to link into the car's current MOST audio system (head unit in the dashboard, also running the car's hvac, and the amplifiers are in the boot)

My second stupid idea was to open up the USB 3 cable and to run individual wires to 3 separate plugs for each of the 3 solutions listed above. At this point many of you may be laughing at my clearly very poor understanding of modern electronics, particularly USB, and I would not argue that at all - I'm a complete dimwit here! Obviously (I think...) the clear solution is in the fact that USB can run different objectives simultaneously,so use a USB 3 hub.

So to the third and hopefully the best idea... instead I run my USB 3 CABLE from the phone to a (presumably powered?) USB 3 hub and have 3 appropriate cables plugged in and running respectively to A/ a USB cigarette lighter socket, B/ an hdmi (or RCA, or composite?) plug and C/ to a standard stereo headphone jack or socket.

I don't think A/ will work because I don't see power going from the socket back through the hub and into the phone. Suggestions welcomed as I can't see how to get power to the phone at the same time as having a USB cable supplying data out. Or is there power over USB through a hub available? Anyway, it's not too important as I rarely leave the house with less than 80% charge.

B/ seems straightforward enough. Cable, hub, cable (hdmi or RCA) screen.

C/ the audio signal then needs to go to an analog to digital / wired to optical adapter (or does it? Isn't the signal coming from the USB hub already in digital form? It's not optical though.) and then a 2 into 1 optical switch (so I can still keep the existing optical output from the head unit) before plugging into the amplifiers. These 2 adapters are easily available through eBay, Amazon or Maplins as far as I can see. The issue I foresee here is will the head unit still be able to control volume, fade, etc of the signal coming from the phone? If the control of the amplifiers happens via the optical cables then presumably that won't happen if I've used a switch to change the source? Would I have to use the phone's volume, balance and fader controls instead? Would taking the output from the phone's headphone socket be of any benefit? I doubt it as the output power from there may be quite a bit higher than that coming from the USB port...

So you can see that I clearly need some knowledgeable direction here or I will be forever going round in ever decreasing circles!

Many thanks in advance for any help given. Cheers, Mark

297 Posts
I haven't read all the way through this, as my eyes are bothering me, but regarding power and data with your phone, a USB-OTG (on the go) y-cable can do power in and data out. I'm using a Bob J gear USB-OTG, and then a Cables2Go Y-cable that are separate to power my Android tablet.

Also, the Volvo guys are in the same boat as you with the MOST interfaces. There's a $600 Denison plug in interface (though I don't know how it works) that will let you tie in--I believe--without having to cut anything.

You can also use a USB-DAC that's compatible with your phone, connected to the powered USB hub and it will make for only a single cable connection.

Good luck!
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