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Old 04-10-2005, 01:33 AM   #6
Scooby Specialist
Member#: 25837
Join Date: Oct 2002
Chapter/Region: South East
Location: Atlanta, GA
1996 SVX L AWD
Laguna Blue Pearl

Default OEM Jacks for CD Changer Input

CD Changer Input Jack, part 1 -- 13-pin

Subaru radios in many older model years have a round, 13-pin mini-DIN jack for an external CD changer (in addition to the built-in CD changer). In the picture in post #2, it's on the right side, next to the antenna wire. Pin-out (the box at the lower right labeled <CN703 13P CONNECTOR>):

People dieveloped a hack to use this jack as an aux input (for an iPod or satellite radio). The simplest method connects just the aux audio into the jack, but requires that you play a silent CD in the stock head unit. The audio from the external changer jack is always connected to the head unit's amplifier. A real external changer uses the data lines on this connector to tell the head unit to mute the radio and built-in CD (and the head unit uses those same lines to send control information to the external changer).

Here's a thread by 'irmiger' for that mod on his 2004 Forester XT: "iPod solution!"

CAUTION: The pin-out of this round jack may be different on radios from different Subaru models/years.

To use this connector "properly" will require that somebody get their hands on the Subaru external CD changer, so we can reverse-engineer the data protocol sent between the head unit and the changer. Read on to post #9, below, for more information.

Originally Posted by vrg3
It looks like the current round connector is the same as the one on my [1993] Legacy, or at least similar. If it is, maybe the info at the bottom of this page can help.

I hooked an iPod to a stock Legacy stereo and had a switch on the dash to switch between normal operation and "Aux-In" operation. The stereo thought the iPod was an external CD player.
The round connector on older Subarus (and other makes, such as Mazda) did use a simple contact closure between two pins, as he described. But that feature went away on newer radios. Subaru radios changed to the new PBUS (digital datastream) method sometime between 1995-2003.

CD Changer Input Jack, part 2 -- 16-pin

Other Subaru radios have a rectangular, 16-pin jack for an external CD changer (in addition to the built-in CD changer). Picture (model number "P123" on front):

(Picture posted by Glenn Wallace in the thread "What is this connector? (WRX stereo)")

Another model:
. [picture link died]
(Picture posted by iamrazor in the thread "connector on rear of MY02 stock in-dash 6-cd...")

Pin-out on ScoobyMods: "CD Changer Pin Outs on head unit"

The "silent CD" hack won't work with this changer jack. As with the round jack, the head unit needs to see a data stream on some of the pins to mute the radio or internal CD and unmute the audio from the external changer.

A little more information in this thread by 'tad_02Wgn': "connector on rear of MY02 stock in-dash 6-cd..."

Again, if somebody can obtain the OEM external CD changer, it will be possible to reverse-engineer the data protocol.

ADDED: leftsquarebracket has figured out the protocol, and successfully built a box to interface external aux sources. See his thread here:
MOD: '02 WRX, auxiliary input WITH iPod control

iPod / Satellite Radio / CD Changer Input Jack, part 3 -- 20-pin

There is Yet Another external CD Changer jack on some recent Subarus. This variation is a rectangular, 20-pin jack. Also used on some models for Subaru's iPod interface and Sirius or XM satellite radio tuner modules.

Picture (connector in lower-right corner):

(Picture posted by Pattali in the thread Japan Subaru Tech mail ?)

Here is the Pin-out

ADDED: The above jpg (captured from the schematics in the Legacy/Outback GX-201SE radio service manual) assigns the pin numbers differently. Here's the pin-out table with Subaru's numbering (thanks to utc_pyro on

Pin orientation is looking at the socket on the rear of the radio:

10  9  8  7  6  5  4  3  2  1
20 19 18 17 16 15 14 13 12 11

 4 NC
 5 NC
 8 BUS -
 9 BUS +
10 B/U

13 NC
14 NC
15 NC
16 NC
19 GND(B/U)

"Smart" Aux-input adapters

The "aux-in hack" could be taken a step further so that you don't need the silent CD. You would need a single-chip microcontroller to fool the head unit into thinking there's an external factory CD changer connected. Such a device could even provide limited control of an iPod using the factory head unit's buttons, and pass status information back to the head unit's display.

Aux-input devices from Hobbyists

Matthias Klumpp gives a wealth of information on the general idea in his website here (click on the "English" link, then look at the "VAG/Panasonic CD Changer Simulator" section). Nothing specific about Subaru radios, unfortunately.

"Michael's Electronics Projects" hosts an archive of Arne Hennig's information on protocols and pinouts for several makes of CD changers. Michael's site also has a forum where people are sharing information.

Another CD Changer emulator project web site.

"Hack your radio" technique

iPod Direct-connection successful! (but VERY difficult)

Aux-input devices from after-market companies

Jazzy Engineering Aux-in Kits

Leptronix Aux-in Kit

PnP, No siient CD Legacy & Impreza Leptronix Aux-In

Compatible with USDM Impreza/WRX/STI 2005-2006, Forester 2004-2006 with the 6-disc changer, and Legacy 2005-2006 2.5GT and 2.5i


For Subaru OEM radios that have the 20-pin changer socket, PAC has the uPAC-SB1, which lets you add up to two new audio sources. The uPAC-SB1 kit includes 1 iPod and 1 Aux cable. You can also connect their HDRT HD radio tuner.

The kit's Subaru-specific cable includes a pass-through socket, in case you already had (or want to add) another Subaru accessory plugged into the 20-pin socket.

Of course, most Subaru radios that the uPAC-SB1 is compatible with already have an aux input.


Module that plugs into the 20-pin changer port and provides two stereo RCA inputs. Only compatible with a handful of Subaru OEM radios.
See this thread: Best Aux in mod for 05 LGT?

[The following links are very old, but I'm leaving this in for now.]

There are a few companies building these too. They're compatible with several different stock head units (each company sells a "main" box with different adapter cables for different makes of radios). But none of these companies has a version for Subaru radios yet. While the actual hardware and programming needed should be fairly easy, the hard part is reverse-engineering the data protocol between the stock head unit and CD changer.
  • BLITZSAFE of America, Inc. [link DEAD]

    A message from a moderator on Blitzsafe's bulletin board, dated 25 October 2004 says:
    As it stands now, I do not see a release of any interfaces for subaru in the near future. subaru is not a large market for us, and the R+D gets pushed back and delayed in favor for more popular applications. When/If I hear more information, I will post up on the message board.

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Last edited by SVXdc; 09-09-2013 at 10:51 PM. Reason: merged the various CD changer jack posts into one
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