Bass preamp circuit subwoofer preamplifier board

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Subwoofer preamplifier with bass preamp circuit filter, ideal for activating active subwoofer speaker, still requires a power amplifier. It has volume and cut-off frequency adjustment. If you prefer, you can change the filter components to the desired frequency. It is configured to adjust from 49Hz to 156Hz.

About Bass preamp circuit subwoofer preamplifier board

The circuit relies on symmetrical power supply using 12V voltage regulators. The power supply should be by transformer from 9 + 9 to 15 + 15 VAC.
IC IC3A is a non-inverting amplifier with 11x gain, IC3B is a Sallen-Key high-pass filter with cutoff frequency = 49Hz, IC4A is a low-pass filter with cutoff frequency = 157HZ, and IC4B is a low-pass filter adjustable from 60 to 156HZ. You can use filter calculators to change the cut-off frequency of your choice.

The voltage regulator can be 12 or 15V, depending on the operational amplifier used. Here in the tests I used the NE5532 IC from Texas and the NJM2068D from JRC.

Subwoofer preamplifier schematic

Bass Filter Circuit Schematic Subwoofer

Suggested PCB for mounting a bass preamplifier

Subwoofer Preamp Board Bass Component View
Subwoofer Preamp Board Pcb Top
Subwoofer Preamp Board Pcb Bottom

BOM to assemble a Bass preamp circuit subwoofer preamplifier board

Last Update: 12/15/2022 12:21 PM

Part Value Description Quantity
Resistors 1/4W
R1, R2, R3, R4, R6, R13 10k Brown, black, orange, gold 6
R5, R7 100k Brown, black, yellow, gold 2
R8, R10, R11 6.8k Blue, gray, red, gold 3
R9 150k Brown, green, yellow, gold 1
R12 47k Yellow, violet, orange, gold 1
Capacitors
C1, C2, C3, C4, C7, C8 100n (104) Ceramic Capacitor 6
C5, C6 2.200uF/25V Electrolytic Capacitor 2
C9, C10 100uF/25V Electrolytic Capacitor 2
C11 10uF/25V Electrolytic Capacitor 1
C12 47p (47) Ceramic Capacitor 1
C13, C14, C16 100nF (104) Film capacitor 3
C15, C17 220nF (224) Film capacitor 2
C18 10nF (103) Film capacitor 1
Miscellaneous
P1, P2 50k Single potentiometer 2
CN1 Power 2-Way Connector Terminal Block 5.08 mm 1
CN2 Subwoofer output JST-XH-03 2.54 mm 2-pin connector or equivalent 1
CN4 Audio Input JST-XH-03 2.54 mm 3-pin connector or equivalent 1
Semiconductors
IC1 LM7812 12V positive voltage regulator 1
IC2 LM7912 Negative voltage regulator -12V 1
IC3, IC4 NE5532N, or JRC2068 or equivalent Dual operational amplifier 2
LED1, LED2 Led 3 mm Led any color 2
B1 DB107 bridge rectifier 1
Solder, Wires, board, box, transformer, etc.

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