50 W transistor amplifier

Description. 

A very rugged and reasonably power amplifier circuit that can be used  for any audio applications. The amplifier produces 60W rms at 50V supply  on a 8 Ohm load.The circuit is designed such that most of the components are not critical and can be easily replaced by nearest values.This make it ideal to assemble from your electronics junk box.

 The capacitor C1 controls low frequencies and capacitor C2 controls high frequencies.The circuit ia basically a class B amplifier.The transistors 2N 3055  serves the function of driving the speaker.The other transistor functions  as pre amplifiers for the  driver stage.This is the basic scheme of the circuit.The maximum power level of amplifier can be  set by adjusting the 500 Ohm POT connected with the BC107 transistor.

 

Circuit diagram with Parts list.

 power-amp-50-w.jpg

Notes. 

  • The circuit can be powered using a 50 V DC power supply with 5A current rating.Up to 60 v can be given to the circuit.Any way the power supply must be well regulated and filters to avoid noise.
  • Adjust the 500 ohm POT  to obtain optimum performance.
  • All capacitors must be rated higher than the supply voltage.
  • Volume control can be attained  by connecting a 10 K POT in series to the input of the amplifier.(Not shown in circuit).

 

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36 Responses to “50 W transistor amplifier”

  • Christiaam says:

    HI sir i domt know what your name is but ive this circuit whouid like to know what is the RMS watts on this amplifier output

  • James says:

    does this circuit work?
    does it have good audio output?

  • george says:

    where do l get power negative

  • PRAMOD MANUJA says:

    HI SIR! HOW TO MAKE REGULATED 50V?

  • RICK says:

    Cool CIRCUIT!!!!

  • seetharaman says:

    TIP41/42 are good output transistors its gain may not be sufficient for driver application. You can try using them. you can use BD139/140 pair you can use BC327/337 8550/8050 CK100/CL100, 2N1711/ 2N1907 etc

  • JOMOTS says:

    HI again sir. I just want to ask if tip41 & tip42 can be substitute to bc286 & 287? thanks!!

  • seetharaman says:

    Hi Anish you require MIC preamplifier with a voltage gain of atleast 100. Because the mic output is around 2 to 3mV. for rated output the above amplifier requirement is around 300mV RMS. Why do you want to use a sledge hammer to hit a fly. you can use amplifier with 1 watt or 2watt capacity that is all what you require.

  • Anish says:

    Can this circuit directly used for an intercom? i.e, connecting a mic at the input?

  • seetharaman says:

    Hi Jomots cannot be used as A733 is an NPN small gignal transistor. You can use BC558, BC158, 8550, BC327, BC328, 2N2907

  • jomots says:

    hi sir,,can i use A733 insted of BC212

  • seetharaman says:

    Hi Sarath try BD137 or 2N1711

  • SARATH says:

    I was trying to make fm 50 watt transmitter circuit.But i could not find the transistor BC286 .can you please help me what can i use insted of BC286

  • rupjyoti says:

    Thank u SEETHARAMAN sir.

  • Seetharaman says:

    Hi Rupjyoti the problem is due to too much of HF response in modern silicon transistors. To avoid RF break through I always recommend a Low pass filter before main amplifier 1K in series with input signal and decoupled to ground with 470PF ceramic disc capacitor. The amplifier should be enclosed in metal chassis with common of the amplifier board connected to chassis at the input socket end. For reference see motional feedback amplifier appeared earlier.
    http://www.circuitstoday.com/motional-feed-back-amplifier

  • RUPJYOTI says:

    SEETHARAMAN SIR,
    I MADE THIS CIRCUT AND SOUND QUALITY IS GOOD BUT LOTS OF NOISE IS COMING WHEN NO INPUT IS GIVEN. WHEN I CONNECT A SOURCE AND MUTE IT SOME RADIO CHANNEL’S VOICE IS COMING, WHAT I DO SIR. (I USE 2.2K AND 22OHM IN THE EMITTER CIRCUIT OF BC212.I USE BC157 INSTEAD OF BC212,BD140 INSTEAD OF BC287, BD139 INSTEAD OF BC286).SORRY BAD ENGLISH

  • seetharaman says:

    Hi Alan For output you can use TIP41B. BC212 can be BC557, BC286 can be BD139, BD287 can be BD140.

  • alandeaker says:

    Hello again
    I’m having troubles with this circuit, I can’t find the exact transistors. I’m think that is the problem.
    Could you give me a list with replaces?
    Thanks

  • gregtherider says:

    HElo!

    If I understand you right you want to know what are the power ratings for resistors?
    As far as I can remember the resistors around 2N3055 transistors have to be at about 5W all others can be 1/4W.

    Correct me if I am wrong.

  • Alandeaker says:

    Hello
    I have a question about this circuit. There are power resistances or what are the power capacity of all resistances?
    PD: Sorry by my bad english, je.
    Thanks and greetings from Ecuador.

  • seetharaman says:

    Hi Kapo both bc286s and bc287 requires small finned TO39 cooling clips. both the power trasistors require extruded aloy large heat sink sitable for TO3 casing.

  • Kapo says:

    Hello
    Could you tell me which of transistors require cooling and what is it

  • john says:

    i want to understand how to make audio mosfet amplifier.

  • seetharaman says:

    Hi Fernandez nano farad – 100nF is 0.1micro Farad. micro farad X 1000 is nano farad.

  • Ezekiel Fernandez says:

    can’t find a replaceable value for those nano farad capacitors

  • Ezekiel Fernandez says:

    Thanks for the reply… i’ll try to seek out the problem…. anyway i think we had problems on the transistor replacements

  • seetharaman says:

    Hi Mr fernabdez you should get 25 to 30 volt at out put transistor emitter resistance junction conection to speaker coupling capacitor positive terminal. if not there is something wrong in the wiring. This circuit is based on philips audio application book 1972. a stable reliable amplifier.
    donot give up please find out the problem and solve it you will appreciate the results.

  • Ezekiel Fernandez says:

    We’re having problems in out audio amplifier and we’re getting 10 – 50 volts DC output….

    • admin says:

      Reply to Ezekiel Fernandez

      There is no problem with this circuit.I think you may have made some connections wrong. Also,you need to adjust the 500 ohm POT for optimum performance.This circuit is successfully tested by many guys.

  • gregtherider says:

    Hi again. Problem solved. One of the BC transistors was fake. I replaced it and now amp is working fine and its fu**** loud!
    Thanks for that circuit!

  • gregtherider says:

    Hi! I built this amp and it`s not working. I triple checked everything and it looks ok to me. But when I connect it to power nothing happens. I measured the standby current(current to the circuit when not loaded) and its very low (4.5mA). Power supply is 35V 5A. I measured all transistors with multimeter and they seem ok.
    Does anyone have an idea what could be wrong?

  • chuan says:

    HI
    This chart uses pspice to simulate may ??
    ok or no
    And tells me All transistor’s function is??

    And tells me the oscillogram the illustration

    Thanks

  • seetharaman says:

    BC212 is for stailising half supply at positive end of spkr coupling capacitor. BC286 is driver, BC286/287 is a complimentry driver for output 2N3055. BC107 is the thermal compensation as well quisent current stabiliser for out put transistor 2N3055s (say around 50mA). The gain of the amplifier is governed by emitter resistance of BC212 2-3K and 20 to 100ohms resistance. you can adjust the ratio in such a way you maintain around a gain of 50, for better frequency response and distortion due to over loads. wish you happy listening.

  • seetharaman says:

    you can use european components like BC177/557/157B for BC212, medium power BD137/BD139 can be used for BC286, BD138/BD140 can be used for BC287 which are quite rugged and reliable. please note these plastic medium power transistors have center lead collector left emitter and right base as you view the leads and metal heat sink portion viewing down. this is a very reliable amplifier. Please enjoy the sound with solid punch and power.

  • Rezwan says:

    Hi, I was trying to build the circuit for 50 W transistor amplifier on Multisim but I couldn’t find transistor BC286 and BC287. Can you please tell me what can I use instead of them? Are there any equivalent transistors? Thank you in advance.

  • Rezwan says:

    Hi, Can you please tell me what each component is doing in the circuit?