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
Suggested PCB for mounting a bass preamplifier
BOM to assemble a Bass preamp circuit subwoofer preamplifier board
Last Update: 12/15/2022 12:21 PM
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|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|
|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|
|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|
|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|
|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|
|Solder, Wires, board, box, transformer, etc.|
Download the files for this assembly, PCB in PDF, PNG, PS and GERBER
- Download PDF datasheet DB107 bridge rectifier
- Download PDF datasheet NE5532 operational amplifier
- Download PDF datasheet NJM2068D operational amplifier
- Download PDF datasheet Lm7812 voltage regulator
- Download datasheet PDF voltage regulator Lm7912
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