First, let's change the pin numbers to match Subaru's wiring diagrams...
Aux/Mic/Sub socket
Code:
Subaru's pin numbering
(viewing rear of OEM HU or wires side of car's harness):
_ ________________ _
| --- --- |
| 8 7 6 5 4 3 2 1 |
|16 15 14 13 12 11 10 9 |
------------------------
Corresponding numbering on PC board:
2 4 6 8 10 12 14 16
1 3 5 7 9 11 13 15
PCB Subaru Description OEM Color
--- ------ -------------------------- ------------
16 1 Mic In (+) White/Black
14 2 Mic B+ (+5V supply) Gray
12 3 Aux In Left + Yellow
10 4 Aux In Right + Blue
8 5 Subwoofer Amp Turn-On -
6 6 Subwoofer Out + (positive) -
4 7 Mic Shield -
2 8 NC -
15 9 Mic In Ground (-) Violet/Red
13 10 Mic Detect Black/Blue
11 11 Aux Audio Ground Shield
9 12 Aux Enable Black/Orange
7 13 Subwoofer Shield -
5 14 Subwoofer Out - (inverted) -
3 15 NC -
1 16 NC -
Most people shouldn't worry about the PC board pin numbers. I've included them here for people who want to match them up to aacordon's picture.
Aux Input
The aux input is electrically the same as in previous years. When you plug something into the car's jack, the jack connects the Aux Enable pin to chassis ground (not audio ground). This tells the HU to let you switch into aux mode. When the enable line is floating (nothing plugged in), the aux button doesn't work.
Note that when there is nothing plugged in, the aux jack shorts the Left and Right input wires to audio ground (to minimize noise going into the HU). Remember this if you want to keep your OEM jack and splice in a second aux device.
To connect the OEM jack to an aftermarket HU, all you'll need are pins 3 (Left), 4 (Right), and 11 (Ground).
BT Microphone Input
We've discovered (see posts below) that the OEM mic is inside a module with a small amplifier circuit. It is not directly compatible with aftermarket HUs.
The car's harness connects Mic Detect (Subaru pin 10, labeled "MIC DET" on the HU's circuit board) to ground. I suspect this tells the HU to enable handsfree functions.
The HU's Pin 2 (what I previously called Mic Detect A -- misleadingly labeled "MIC DET" on the circuit board) sends +5V to power the mic module.
Pin 1 is the audio signal (+) from the mic to the HU. Pin 9 is the ground for the mic and its amp circuit. See pictures and posts below.
Subwoofer Output (not functional on this Impreza HU)
The sub out is the same as on the Impreza/Forester Navi HU and some recent Forester non-nav HUs. The output is balanced (differential) mono. It is
not left and right stereo.
To connect to an amplifier that doesn't accept a balanced signal, send the HU's positive output (pin 6) and the shield (pin 13) to your amp's line-level input. On the Navi HUs, tying the inverted output (pin 14) to the subwoofer shield will increase the signal on the positive output. That will likely work for this HU too.
If your amp has two inputs, you may need to use a Y adapter to feed the OEM HU's positive sub out into both of the amp's inputs. Do
not connect both of the HU's outputs into separate inputs on the amp -- the signals will cancel each other out, and you won't hear anything.
Pin 5 is a standard amp remote turn-on (has +12V when your HU is on). You can use this for a speaker amplifier or other accessories. Watch your current draw -- I recommend staying under 200mA total. If in doubt, use a relay with a low-current coil (not one of those monster 30 Amp automotive relays).
It's a good bet that the aux/mic harness in some 2011 Forester models will have wires on the subwoofer pins.
It looks like the Impreza HUs don't get the sub output. So the upcoming subwoofer accessory for Imprezas will probably have a T-harness that taps into a pair of the main speaker outputs
