STK4231II 2 channel 100w stereo audio amplifier circuit

If you want to create the 100 watt OCL audio amplifier circuit. I have many circuits for you, transistors, and ICs.

Now using IC is a better choice. I want you to consider this circuit.

It uses the STK4231 chip to create a simple, small, without adjusting, and economical.

STK4231II stereo audio amplifier circuit

How it works

The STK4231 is a Hybrid IC of Sanyo, in the family of STK4201II. It can provide a high power output of 100 watts per channel.

And When connected to the bridge adapter. The its output altitude up to about 400 watts (It’s incredible).

The feature

It has main feature.

  • Built-in muting circuit to cut off various kinds of pop noise.
  • Greatly reduced heat sink-due to case temperature 125 degrees Celsius.
  • Excellent cost performance.

As this circuit, we can design the OCL amplifier 100 watts each channel. You will see that, this circuit consists of only a few external components.

Some detail may help you easy.

  • The capacitor C9, C10 is used to reduce noise at high frequencies.
  • Both C1 and C11 are the input coupling capacitors.
  • The C2, C12 is defined for low-frequency cut-off point.

Which we can calculate from the formula :

F=1/6.28 C2xR5

2 channel 100W STK4231 amplifier circuit


  1. Both capacitor C2, C12 is defined gain ratio at low frequency. But they must do not over high.

Because, while open this circuit. It will be has a noise “thub…b.b.b” out to your speaker.

2. And both C3 and C13 are the boost trapping capacitors. If this value is too low. It will make more distortion at low frequency.

Then, both C5 and C8 capacitors reduce oscillation. Which, it will reduce the impedance of the power supply circuit to suit the use of IC.

Setting the gain ratio of the circuit.

It is defined by R5 = 560 and R4 = 56K. They will be total gain is VG = 40dB.
If you want to change the rate of expansion, it should change the R5.

Change idle current is defied by R21 and R22 resistors.

Hey! Oh… Is it too large circuit for you, Right?

Look below: You may like it.

TDA2030 Stereo Amplifier with PCB


Caution! This project needs to use the speaker protection circuit. Otherwise, your speaker may be damaged.

The power supply circuit

In this circuit requires the dual power supply circuit (positive – negative 50V and current is 5 Amps.

See the circuit below.

STK4231II 50V Dual Power supply circuit
STK4231II 50V Dual Power supply circuit

How to build

It’s very easy to build, even if you are a beginner. It is important to place the devices correctly follow the circuit diagram.

In this figure is PCB and putting position the parts.

Here is Copper PCB Layout

Copper PCB layout of STK4231 amplifier

Then see components layout.

STK4231 components layout

Shopping list

25W Resistors, tolerance: 5%
R1, R4: 470K
R8: 100Ω

Ceramic Capacitors
C9, C10: 470pF 50V

MKT (Metallized Polyester Film Capacitor)
C4, C14: 0.1µF 63V

Electrolytic Capacitors
C1,C11: 2.2µF 25V
C2, C12: 100µF 25V
C3, C13: 47µF 25V
C5, C8: 10µF 63V
C6, C7: 100µF 50V

Semiconductors and others:
IC1: STK4231II 2-Channel 100W min AF Power MODULE
L1: 3uH inductor


The IC STK4231II should be installed with the big heat sink.

Thanks a lot: Prakit Book

You may like these circuit, too.

Other circuits are recommended

More Audio Amplifiers with PCB

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I always try to make Electronics Learning Easy.


  1. Please share me the PCB Circuit layout for the STK4321 MK 2 as i will love to try the Making of PCB STK4321 MK2 ..

    Rakesh Sharma
    Call + 91 9762089423.

  2. in this circuit how to use 5.1 hometheater used,with stk4231 ic and 8 inch subwoober,and with 100 watts only other speaker or how to use wstts.

  3. Bala

    STK4231 original ic how much price?

  4. hai friends iam raju from yuvaraj bisnes stk amplifiers i want stk 4231-11 components pcb boards please any infarmation

  5. Dear,for assembling STK-4231-11,can i use the same pcb configuration used forSTK4141-11?Because i had a stk 4141 circuit working with 30V/5Amps Dc Dual supply,that ic got may be replaced.STK 4231,is it available at kolkatta market?

  6. prashant

    Where availabel at mumbai stk 4231II ic and all type high waatt ics please give me address my self prashant

  7. mohammad

    this ic (stk4231II) IS 200000 rials in iran.
    thanks for your great circuit.


    where can i get panasonic sa-vk800 multi amp system STK 470-090 IC

  9. david

    hi. why pin 16 is connected to -50v in pcb and top silk but in schematic pin 16 of stk isn’t connected to -50v? and another question that why do you use 100uF capacitor except 10uF(C7) in top silk?please help.

  10. shanmugam

    please suggest any 5.1 audio for 100watts

  11. david

    Hi momename
    please help me faster.I bought it’s components and I dont know
    what to do?I need your help.

  12. david

    Hi momename
    i made this circuit according to the top silk
    that you had put in this part for stk.
    now I want to say if others want to make this circuit;
    please follow the top silk information.
    when i wanted to start this circuit;suddenly I SHOCKED
    make this circuit and enjoy of it. thank you very much momename for your great amplifier circuit.

  13. pradeep

    where shall i get 4231 ic build amplifiers in chennai market or inside tamilnadu

  14. Ankit

    Should pin 16 shouldnbe connected or left opened….?
    And i am following the schematic diagram i.e. the first is it correct?

  15. a.raghunath sharma

    is stk 4321 mk II available in kolkata

  16. Ankit Chheda

    I made the circuit but its not working…i tried with schematic , top silk and the bottom layer but the resistor R10 is getting burnt and the ic is getting heated…please help as soon as possible…!

  17. Ankit Chheda

    The value specified for R10 is 1 killo ohms i also tried with 10killo ohms…that also is getting burnt…please help

  18. rico

    how many current in stk4231 audio amplifier max.

  19. janak dave

    STK 4231 redi avelebal he to context mi hame chahiye holsel my cnntect no 09427388905

  20. A.Raghunath Sharma

    you will get all stk ics at

  21. Ashik

    Bangladash market price only $3.00. Thanks.

  22. Shanmuga

    Sir i am desired used this ic to subwoofer for 5.1 system pls said transformer rating alsow which ic used to other 5 channel for 5.1 system

  23. sir gud pm

    value of resistors is it 1/4 watt or 1/8 watt and for capacitors how many volts do i use

    tnx and god bless

  24. saeed


    what is the speakers specs?
    the input in voltage is 50+ 50- , but what is the input in Amps?

  25. Rolly

    What is the size or watts of R3,R13,R7,17?

  26. siva

    how many 8″ speakers may connected in stk 4141

  27. HK

    what abt no.8 pin (Mute)….? how to open this point…by giving +5V supply or not..???

  28. saom visak

    now i want to adjust bass, volume but i don’t know how to do that , Could you recommend me?

  29. DIl

    I want to make a 50+50W amplifire please give me a link there is details

  30. Bernard de Grasse

    Hi.I live in London England.Is it possible to buy the Pcb and components including speaker protection circuit for TDA2030 100w stereo amplifier with PCB.If so How mutch in £ wiil it cost.Thanks Bernie

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