Mini subwoofer circuit using LF347N

This is mini subwoofer circuit stereo for home using low noise LF347, it can select frequency output filter is 60Hz,50Hz and boost up preamplifier.

Almost everyone like sound realistic, particular the low frequency sound signal is system that commonly widely used. With how to bring out the low frequency signal. from amplifier circuit both left channel and right channel come Enlarge together, And then enter to speakers are designed for Low Frequency, particular sound from the subwoofer speaker, will cause the sound system vibrate up. But increased sound quality. Inevitably requires a more money as well.

How it works
But for those who has less money, you can build a subwoofer an artificial. Our method is simple, Will help raise the low frequency sound signals to considerably higher special. From circuit will see the input signal is entered into the input buffer circuit. Which will provide the signal gain at frequency The output from buffer circuit will enter to low pass filter circuit that will refusing to pass a signal at a frequency lower than 60Hz only. The output of low pass filter will be entered to the mix with the normal signal from the amplifier input circuit, to the signal complete all frequency range.
In figure 1 shown the perfect stereo system circuit. From circuit will seen that IC1a(TL074) has gain at higher frequency than 60Hz = 1 and the amplify rates of the circuit, will gradually increase the frequency below 60Hz. Compensation for the performance of the speaker, at low frequency response reduced.



The output of IC1a(TL074) some one will enter to the low pass filter circuit IC1b and IC2a, which allows only frequencies below 50Hz through.
The IC2b(TL074) is the total output of IC1a and IC2b, joined together, Switch S2 is used to adjust a bass level much or less as needed.

Mini subwoofer parts


IC1, IC2: LF347N OR TL074 or TL084 Quad JFET Input Op-Amp (Wideband)
0.25W 1% resistors
R1, R26: 47K
R2, R25: 270K
R3, R24: 56K
R4, R23: 11K
R5, R7, R20, R22: 68K
R6, R21: 36K
R8, R19: 680 ohms
R9, R18: 1.6K
R10, R12, R15, R17: 10K
R11, R16: 390 ohms
R13, R14: 1.2K

Polyester MKT Capacitor
C1, C12: 0.33uF 50V
C2, C11: 0.047uF 50V
C3, C5, C8, C10: 0.47uF 50V
C4, C9, C13, C14: 0.1uF 50V
C6, C7: 0.01uF 50V

How to build
In figure 2 Show the PCB design and equipment position. We are equipment installation all the is required by Circuits.
Connection to use it if pre-amplifier circuit and power amplifier as discrete set to connected this circuit before the power amplifier circuit.
If the amplifier is integrated to connect these circuits into the Aux input.
Note: Due to a bass signal is enhanced more than 10 times so the output may have a higher signal than 10 volt, which may make the speaker has suffered, in the deployment so it should be extra careful.

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9 thoughts on “Mini subwoofer circuit using LF347N”

  1. sir it this subwoofer stimulator is to connect before any power amplifier or is there any specific amplifier for this

  2. Hi,

    Thanks to prompt response and your guide.

    My board is ready to connect. Can I used for checking purpose 15 -0 – 15 transformar make diod briz.

    Can I add this simulator output point before 1230 audio chief ic which work on 12 v dc allready I have two set of this audio board.

    If any change in this circuit too add before 1230 audio chief pl. Write.

  3. It’s no problem to connect the supply at 12V because only will reduce your voltage swing and maybe affect the performance of total harmonic distorsion very little. If you use a dc dc converter to step up voltage at 15V, you will generate noise that will entry into opamps because of poor PSRR.


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