PART 2 – ADDING AN AMPLIFIER / SUBWOOFER
THE OEM “AUDIO UNIT”
The “Audio Unit” (as named in the FE Service Manual) is the box with the CD player which also contains the amplifier in the non-Sony system. Though other components (MFT Screen, dash controls, steering wheel controls, SYNC APIM (allowing voice command), etc) are integral to the operation of the overall system, the “Audio Unit” is the closest analogy to a traditional “head unit” in the non-Sony FE entertainment system.
+ It should be noted that the FE audio system is mainly controlled by the digital-logic canbus, not by ‘traditional’ electrical switches and analog electrical signals.
+ The FE amplifier/speaker system is “on” whenever the car is running in order to support SYNC-to-driver communications through the speakers. The system automatically turns “on” due to canbus commands whenever a door is opened (or the remote is used to unlock a door) and remains on for a pre-determined period of time if no other action is taken, then it turns “off”.
CONNECTING AN EXTERNAL AMPLIFIER
+ There is NO analog pre-amp output from the FE Audio Unit; even if there were, by definition a pre-amp output is ‘line level’ and would sacrifice all of the convenience of the MFT, steering wheel, dash and voice controls for volume, balance, fade, treble/mid/bass, etc.
+ Therefore it is necessary to use either 1) external amplifiers which directly accept speaker-level / high-level inputs; or 2) a Line Out Converter (LOC) between the Audio Unit and the amplifier low-level (RCA jack) inputs. The option of installing a Digital Signal Processor (DSP) is beyond the scope of this discussion.
+ The speaker-level output wires from the Audio Unit are in connector “C240A”; see the post above, Part 1, ACCESSING SPEAKERS, last bullet about accessing the front center speaker for how to remove the dash panel to expose the Audio Unit.
+ See the attached pics for an example of making input-output connections for an external amplifier at connector C240A, including a wire color chart.
EXTERNAL AMPLIFIER POWER SOURCE
+ Most automotive audio guidance suggests that added audio components be powered by a fused power feed directly from the battery in order to avoid noise (buzz, whistle, hiss, etc) which can easily be introduced if power is tapped from an existing fuse box or other 12 volt source. Therefore I will not discuss alternate sources of 12 volt feed for added components.
+ Forum member markboris shows us how to get through the firewall with a power feed from the battery in this post How to route front camera wires into the cab?
EXTERNAL AMPLIFIER ‘POWER ON’ CONTROL
I have not found a dedicated DC output which is analogous to a ‘remote power on/remote power antenna lead’ as found in some audio head units and commonly recommended as a source for a ‘remote power on input’ for external amplifiers. Some alternatives for power-on control are:
+ Tap BCM unused fuse slot F87 – this fuse is hot only when the ignition is on. Note this means that you will not get speaker sound /SYNC sound info as you would for a certain time before you start the car and after you shut it off like with the OEM system. You would not be able to play music at all with the key off like you can with the OEM setup.
+ Tap one of many “always on” circuits and add a manual turn-off switch – with the obvious great risk that if you forget to turn-off the system you’ll kill the battery.
+ Use an amplifier with speaker-level inputs that includes a feature sensing current in the speaker circuit to turn-on the amp. Current is present on the speaker wires when the Audio Unit is “on” even when no sound is present. Many offer this, for example the Alpine MRV-F300 4-channel amp and the Alpine PWE-S8 powered subwoofer (Google those models for more info). Both those components work flawlessly in my FE to exactly mimic the operation of the OEM system with zero turn-on pop, delay, sound clipping or other adverse effect. In addition, if the entertainment system is told to ‘shut-down’ by the FE battery-saver feature that will automatically also shut-down the added components.
+ Look for a separate device that uses the speaker-sensing technology described above as a turn-on trigger. The PAC TR-4 might work (I have NOT tested that device). Pac-Audio.com Product Details | iPod Integration for your car and More by Pac-Audio - Connecting you to the future
+ Most automotive audio guidance suggests that all audio components be grounded to the same point to help avoid ground-looping which can induce noise in the system.
+ The audio components in the non-Sony FE all use the same grounding point, located under the carpet near the front of the driver’s door sill. Pry-up the plastic door sill on the driver’s side and pull-back the carpet that tucks under the sill in front of the seat. You will see three grounding screws in a cluster – the front-most screw, the only one with three separate wires under it, is the FE audio system ground point. Remove the screw, add your ring-end ground-wire connectors to the stack, route your ground(s) under the carpet. FWIW I didn’t even try another ground – I used this point for each separate ground wire to my added amps and have zero noise from the system.
Sorry for the long posts but I hope some will find the info helpful. Each step of my audio system upgrade yielded better sound in my FE. I’ll soon do a post in the “Electronics, Audio, and Lighting” subforum describing my completed audio upgrades.