DIY Aux Cable for Audi A3

The main (annoying) problem that I’ve had after changing to my Audi A3 Sportback is that my music options have been restricted. The Audi has an “Aux” input so that you can hook up an external Audio source to the car. Now here lies the problem(s)

#1 – I had to find a cable. No problem, rummaged through the old boxes, found one #Winner
#2 – Cable plugs into the Aux in car, when attempting to connect to the SamsungS7 it’s too small….. shit!
#3 – I don’t have an adapter cable for Samsung S7 to 3.5mm…. double shit!!

Now, I’m not one to admit defeat, so I needed a solution. Time to bodge it

  • Old pair of Samsung S7 Headphones – Check
  • One incompatible 3.5mm to 3.5mm Cable – Check
  • One person who likes to modify and hack stuff so it works. DAMN RIGHT!

Now, there’s one main problem even after all this. Which I don’t think is a problem as such, I think it’s just the design of the connectors (or I’ve soldered them wrongly). I’m going to mention it here however, just as a guidance note, and for future input if anyone who understands it better than me can clarify. Basically when soldered together, I used the multimeter to check for continuity between each individual connection. As they are isolated, there should be none except for the points. The Samsung S7 has one point which isn’t soldered anywhere which is the Mic connector.

All the other three points I soldered from the TRS Jack to the TRRS Jack and their appropriate connectors. When I tested for continuity however, I get continuinty between Ground and the Right Channel on TRS/TRRS. I have grounds themselves, and the solder points are fine. So I’m not sure if I burned through the insulation, or if it’s because of the type of jacks I’m using. I did a quick search online, and the grounds themselves on diagrams are both linked up to the actual L/R channels anyway. The comments posted said there’s no issue soldering L/R to Ground, as long as you have continuity between the Grounds. I did so I’m happy with that. I’m just noting this here, so if anyone else attempts this modification, they’re aware of any potential risks or damage to their vehicle. I’m confident it won’t cause damage so I’m happy to continue using it.

Here’s how I made the Aux Cable. First I had to identify the connectors which correspond to the wires (Found here). So, the standard connector I have is a TRS (Balanced Mono) and the Samsung S7 appears to be a TRRS connector (Balanced Stereo). Get the old multimeter out, and run continuity tests between the individually isolated terminals, and their corresponding solder points/wires. This allowed me to identify the Ground, Mic, Left and Right Channels

Just as a note, I was intially going to solder to the wires. The cables in the Samsung S7 Headphone cable however are ridiculously thin. So I ended up snipping it until I got to the plug itself and soldered directly to the jack. Much nicer and looks way better in my opinion

Does it work? – Yes. I had to slightly fine tune mine as the balance was off slightly. I had to fade it to the left by 1 bar. Otherwise it’s nice and clear and loud now. I recommend turning your Volume up to it’s maximum on your phone after it’s plugged in, as it’s quiet when left on “normal” volumes.

If you are planning on making your own Aux Cable, I’d suggest buying TRRS connectors so that when you solder them it’s just a straight connection to connection, and each individual wire is isolated. Also for the cable, you’d need some kind of speaker cable with 3 cores (One for left, one for righ, one for ground).

If you’re here for the pictures of this modification, see below.

Just as a future note, this DID work, but it was only a temporary measure. I ended up buy an Aux Cable from eBay that was braided. Here’s a similar one on Amazon

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