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
Bass Filter Circuit Schematic Subwoofer

Suggested PCB for mounting a bass preamplifier

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

BOM to assemble a Bass preamp circuit subwoofer preamplifier board

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

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PartValueDescriptionQuantity
Resistors 1/4W
R1, R2, R3, R4, R6, R1310kBrown, black, orange, gold6
R5, R7100kBrown, black, yellow, gold2
R8, R10, R116.8kBlue, gray, red, gold3
R9150kBrown, green, yellow, gold1
R1247kYellow, violet, orange, gold1
Capacitors
C1, C2, C3, C4, C7, C8100n (104)Ceramic Capacitor6
C5, C62.200uF/25VElectrolytic Capacitor2
C9, C10100uF/25VElectrolytic Capacitor2
C1110uF/25VElectrolytic Capacitor1
C1247p (47)Ceramic Capacitor1
C13, C14, C16100nF (104)Film capacitor3
C15, C17220nF (224)Film capacitor2
C1810nF (103)Film capacitor1
Miscellaneous
P1, P250kSingle potentiometer2
CN1Power2-Way Connector Terminal Block 5.08 mm1
CN2Subwoofer outputJST-XH-03 2.54 mm 2-pin connector or equivalent1
CN4Audio InputJST-XH-03 2.54 mm 3-pin connector or equivalent1
Semiconductors
IC1LM781212V positive voltage regulator1
IC2LM7912Negative voltage regulator -12V1
IC3, IC4NE5532N, or JRC2068 or equivalentDual operational amplifier2
LED1, LED2Led 3 mmLed any color2
B1DB107bridge rectifier1
Solder, Wires, board, box, transformer, etc.

Download the files for this assembly, PCB in PDF, PNG, PS and GERBER

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