Low Pass Filter Design by JLCPCB

Introduction: Low Pass Filter Design by JLCPCB


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This is a simple L.P.F based on
op-amp TL072/NE5532. Main purpose of this circuit is to provide Low Frequency output to the amplifier. Bass sound in the subwoofer is actually due to this circuit, the op-amp gives the sound with high gain, so that the amplifier gives a very good bass response even at low volume.
It throws the Low Pass Frequency around 160Hz and totally blocks the high frequency and the middle range frequencies.

Note: This is a low pass filter only and its output is only a few milli volts and for this you need to connect its output to the power amplifier

Why it is needed?

Every good subwoofer amplifier must have this low pass filter circuit because it is the only one which can provide a pure and a mirror cracking bass effect. You also make a simple RC filter for this purpose but it will never give a pure effective heart thumping bass output So, must use this great circuit for a good amplifier design.

Regulated Power Supply

Why it is needed in this circuit? (The Circuit Diagram is included)

It is needed in the circuits where you are using the op-amps such as in this circuit of 2.1 amplifier we are using op-amp (operational amplifier) TL072. The regulated supply is necessary for these op- amps because it gives constant and a filtered output to the op-amp so that it works fine without any noise. Here we are using most common regulators 7812 & 7912 positive and negative voltage regulators respectively. This is the reason that in any of the good brand subwoofer amplifier you will see this regulator circuit for smooth output of the op-amp.


The PCB board used in this project is provided by jlcpcb.com and it is the 2 layer board in which you do not have to put any of the jumpers on the board and the board's quality is great due to which the Low Pass Filter's quality is great and totally noise proof. If you want to make your own custom based board the you must visit www.jlcpcb.com and order your first 10PCB boards only for 2$ and without any shipping costs.

BOM's (Build On Materials)

Tl072 or NE5532 or 4558 (OP-AMP)

7812 (Positive Voltage Regulator)
7912 (Negative Voltage Regulator)

Resistors (All are of Quarter Watts)

  1. 33K
  2. 4.7K
  3. 470Ohms
  4. 10K X 4


  1. 0.1UF X 1
  2. 10UF X 2
  3. 220N or 224K
  4. 104 X 2

Step 1: Solder the 220N Capacitor

Pick up a 220N or 224K Non Polar capacitor and firstly, mount it on the PCB board by soldering it with the soldering iron.
You can also use the other value capacitor here but that should be less than 220N and not more than that value and should be a non polar capacitor.

Step 2: Solder All the Resistors and 100N Capacitors

Now, Solder all the capacitors in the circuit along with the 104 or 100N non polar capacitors including the IC jack and the LED.
Firstly pick up 1K resistor and solder it, after that solder the 33K, 470Ohm and 4.7K resistors because these resistors are placed along each other on the PCB board, Now solder the 10K resistors and now you are done with all the resistors, capacitors and the IC (Op-Amp) jack.

Step 3: Solder the Polar Capacitors 0.1UF,10UF

There are only three polar capacitors in the whole circuit one of them is at input stage which is of 0.1UF/50Volts and the remaining two are in the regulated power supply stage with the value 10UF/50Volts
Firstly, Solder the 0.1UF capacitor and then solder the two 10UF/50Volts capacitors.

Step 4: Solder the Voltage Regulators 7812 & 7912

As in the description it is mentioned that this circuit uses the regulated power supply to run and this regulated voltage is obtained from the 7812 and 7912 Voltage regulators
7812 is the positive voltage regulator where as 7912 is the negative voltage regulator
So Firstly, Solder the 7912 Regulator and then the 7812 regulator.

Step 5: Mount the TL072 (Operational Amplifier) on Its Jack

Now Finally, Just pick up the operational amplifier and mount it on the Jack and the circuit is now completed and ready to work.

The PCB Board used in this project is manufactured by JLCPCB
which is the leading manufacturer of PCB boards and produce a very good quality PCB boards at very cheap price and you can order your own designed PCB to their website www.jlcpcb.com and you can avail their offer of getting your first 10PCB's order only for 2$ without paying any shipping costs. Order Now to get 10 PCB's for 2$ only by JLCPCB

Step 6:



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    2 Discussions

    I would like to make the following suggestions.
    As tytower, I'am a bit disturbed by the power supply part, and especially by the fact that the 0vcc (ground) is floating with respect to the transformer. I suggest to use a more simple and adapted design (e.g.. one diode for +side, and one diode for -side ; this should work considering the low current).
    The author should also update the schematic which does not correspond to the actual design (eg. 3300uF/50v).
    The second order active pass filter is rather unusual, with capacitors of different values : 10nF and 220nF. I suggest to use capacitors of same value and to recalculate the capacitors (in addition, with the indicated values, I do not find the cutoff frequency of 160 Hz, but, I'm may be wrong).

    Personally I'd like to see a move to LM1117 type voltage regulators as when they blow they don't pass full voltage to the rest of the circuit