BMW E46 HK E46/4 Amplifier

E46

BMW E46/4 (sedan) HK 2-channel Subwoofer Amplifier

TL431 is a adjustable shunt reference most likely used to set up a virtual ground of around 6 Volts since normally you would want + and - voltage for the audio circuits.
LM3900 is a generic op-amp with 4 in one package
LM13700 is a transconductance amplifier with linearizing diodes and buffer with two independant circuits in one package. This is most likely used as a VCA or voltage controlled amplifier to handle the boosting of the bass in response to the vehicle speed.
LF347 is a general purpose J-FET input opamp with 4 in one package.
LF353 is a general purpose J-FET input opamp with 2 in one package.
TDA8563Q is a 2-channel power amplifier with up to 40 Watts per channel into a 2 Ohms load.

The amp is from NXP, and even though it's advertized as 40 Watts x 2, it's probably more realistically like 20 Watts per channel into 3 Ohms.

X18774	Description	Wire Size and Color
1	SUB_IN+	0.5 GN
2	SUB_ON	0.5 WS
3	no connect
4	Ground
5	Fuse 41 - 30A	2.5 RT/GN
6	SUB_IN-	0.5 BL/GN
7	TAA, Speedometer signal	0.35 SW/GN
8	no connect
9	Ground
10	no connect

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