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Pacific Accessory Corporation
Page 1
Rev: V1
Date: 091120
Advanced Subwoofer Amplifier Interface
for Select Ford Vehicles
APSUB-FD21
The APSUB-FD21 provides a 2-channel non-fading pre-amp output for use with an aftermarket amplifier and
subwoofer. Using the full range, fixed level head unit output, in conjunction with CAN messages, the APSUB-FD21
delivers a low pass variable 5v RMS pre-amp output with bass equalization and level control capabilities. The signal
has a 350Hz / 24dB Linkwitz-Riley low pass filter applied. A data controlled remote amplifier turn on wire is also
provided by the APSUB-FD21.
Introduction and Features
Important Notes
1. This interface is only compatible in vehicles equipped with a data bus controlled premium sound system. To verify
compatibility, look for a Sony badge on the door speakers, center speaker, or factory subwoofer, in the 2019-2020
Super Duty trucks and Mustang; look for a B&O badge.
2.
The factory amplifier must remain connected, and in the vehicle after the APSUB-FD21 has been installed.
3.
The remote output is rated at 2A of current. If more current is needed an external relay must be used.
4. The remote output may remain active once the key has been removed if the vehicle needs to pass chime or SYNC audio.
5. The subwoofer outputs are non-fading. The output level of the subwoofer channel can be controlled using the supplied level
control knob. If the level control knob is not connected the output level will default to 100%.
6. The minimum volume level is set to a default. If you are happy with this level in your particular application then additional
adjustment is not required. Please refer to the Setup and Configuration section on page 2 for more details.
7. Ford Focus:
You cannot use the steering wheel controls to activate the minimum volume adjustment.
8. The level control knob must be connected in order to manually adjust the minimum volume settings.
9.
The factory radio's speed controlled volume and surround sound mode are not supported by the APSUB-FD21 outputs.
10. No adjustments can be made manually using the programming button, or the factory SWC when the module is connected to
a PC.
To Aftermarket
Amplifier
Subwoofer Outputs
Remote Turn On Output
2A Max Output
To Vehicle
Harness
To Radio
To LCD
Screen
Non-Fading
Level Control
Knob
To Vehicle
Harness
AP4-FD21-HAR
The aftermarket amplifier must have a very solid ground and the amplifier power/ground connections
should be made before connecting the RCA's or Remote Turn On to the APSUB-FD21
