Many Electronic circuit projects in simple ways of learning

4 Preamplifier circuits using Transistors

If we want a good quality sound system. The first thing that we should choose, the good pre-amp.
Some people said It is not necessary. But when the low-level audio source.

We may need to adjust the sound too high. It may cause distortion. Thus should have the preamplifier to amplify a signal up before to our power amplifier.

And I use transistors to build as small pre-amplifier, because:

  1. I am familiar with it than other devices. Even though the quality is good.
  2. There are many to choose for creating circuits.
  3. Lower noise, compared with ICs.
  4. Cheap, easy to find accessories.Seeing these advantages. Let’s consider different circuits. For example, I would suggest the following.


1.) Pre Amplifiers circuit Diagram using Transistor

When you want to increase a sound signal from all source, before to a power amplifier.  We often use Pre Amplifier or Pre Amp.

Today we look another one circuit.  It is interesting because using only one transistor.  If you do not have this one(2SD30). You may use others one such as 2SC1815 or 2SC945 or 2SC828, etc.

In the circuit above is Mono system. If you want a stereo. You need to build other one Mono. Which this is an easy circuit.

Pre Amplifiers circuit Diagram using Transistor
Pre Amplifiers circuit Diagram using Transistor


We can connect the output of circuit to the input of power amplifiers.  For the input signal should be enough high level such as from CD player, cell phone,  and more. It is not suitable for low signal. Because of low gain.


2.) Simple pre-amplifier using BC547 transistors

This is a higher preamplifier circuit.  Also to increase a small audio signal to strength to go into a power amplifier circuit.

It is suitable for a tuner, tape etc. That was the strength of input signals in μV to rise to mV.  It can access efficiently to a power amplifier.

Simple pre-amplifier using BC547 transistors
Simple pre-amplifier using BC547 transistors


How it works
First of all, enters a 9V power supply to the circuit. Both Q1 and Q2 to a direct coupling circuit to transmit better.

When the signal input through the C1 coupling into the signal to Q1. It amplifies a signal to a higher level at the collector(C).

Then,  the signal comes into Q2 as the second amplifier.  Next, the signal to leave the output C of Q2. To pass the C6 coupling signal from the output. And some signal at the output of Q2 will feedback through to the C4, C3, and R3. It comes to pin E in Q1 in order to help the range of frequency response.


3.) Simple Preamplifier Circuit using BC548 Transistors

This preamplifier circuit with two transistors. It uses a single supply source from 6V to 12V, at the current minimum is 2-3 mA.   It can extend the signal strength max 2V.

This will drive easily a signal to a power amplifier. The frequency response is from 70 Hz – 45 kHz at -3 dB. It has a distortion of less than 0.1%.

Simple Preamplifier Circuit using BC548 Transistors
Simple Preamplifier Circuit using BC548 Transistors

How it works
To begin with enters a supply voltage to the circuit. Second, to bring an audio source to Input. The signal is coupling through C1 to prevent DC voltage to disturb in the circuit.

Then, audio goes into the lead B of Q1 to amplify signals to forces up, with the R1 and R2.  They are the organized bias for Q1.  Both  Q1 and Q2 transistors connect together in a direct coupling form, to improve audio response.

Next, the signal is increased out of lead C  of Q2, and through C5 coupling the signal to smooth up.  Then, send it to output.   The gain of the circuit can be set from the R6/R5.

For capacitor C3 to improve a high-frequency response better.

Resistor-R9  bring a supply voltage and limit the current to connected to the circuit when the circuit for the condenser microphone. If you do not use it can remove R9 away.


4.) Cassette Preamplifier circuit using BC109 transistor

Cassette Preamplifier circuit using BC109 transistor
Cassette Preamplifier circuit using BC109 transistor


This is circuit Cassette Preamplifier. I used transistor BC109 main part electronics.

It is very easy preamplifier for cassette tape or car audio. But is an old circuit, I like this circuit because it is classic.

What is more? We always have many ways.
If above low gain for you.


Thay has a tone control circuit.


Try IC version: Preamplifier circuit using op-amp

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This Post Has 21 Comments

  1. Thanks a lot. It is working fine. Simple and elegant.

  2. is it fine if I use it for 2.1 stereo system ?
    please mail me 🙂
    thanks anyway ,,,,

  3. can you give the procedures and parameters in making this simple preamp by transistor.

  4. i think i cannt get transistor bc 579

  5. i want preamfilier so simple

  6. BC549 can be replaced by BC547, 2SC9013, 2SC9014, C945, 2N3904, 2N2222, KT312. BUT BELIEVE ME BC109 AND C9013 WORKS AWESOME

  7. Dear Sir,
    I want to prepare a small speaker for laptop,
    and that’s speaker power supply will form laptop USB.
    Please send me in my mail the circuit diagram with sweat able speaker watt & ohm’s

  8. I have to thank you very much

  9. fabulous—-been searching for a simple pre-amp
    using bc 547/557 transistors–
    I built a similar one—-3 transistors



  11. I have a CCTV DVR for security cameras. I am looking for a very sensitive Mic preamp circuit that can be used in conjunction with a CCTV DVR 8 channel. with Very high adjustable gain.

  12. I have one made of a cd panel, is good for a tablet or a preamp for my sound system… Good by noise…

  13. Hi,Martin.
    Thanks for your feedback.

  14. Thanks.

  15. the circuit I would like to assemble , I will test the same and if it is up to my satisfaction I will sand feedback. thanks.

  16. Guys as pre amplifier for dynamic microphone i think we can use a circuit with just one bc109 cuz i was test it for electric guitar and i was get great classic sound with no any noise of electric guitar and i more like to use iron bc109 its more better.

  17. Can use simple power of 12v in 4558

  18. For preamps to be any good, a tone control needs to be incorporated. Its no good if you cant alter the treble or bass to your requirements. Pre-amps with tome controls included can be obtined quite cheaply from suppliers such as Maplin if you are having trouble building your own.. I have tried out lots of preamps from the internet, including commercial ones but mosty they are far too noisy and full of distortion. A preamp needs to have at least a 1 volt output, with a frequency response of at least 20Hz to 25KHz. Most advertisers on here, omit to mention this, and mostly their cheap designs do not meet these requirements. Most of the better preamps need a 15 to 25 volt smoothed power supply. Main amplifiers for home use only need to have about 10 watts maximum output and this will be found to be more than adequate, and because you are not using a shed load of current/Power, it will be much cheaper to run. Have fun. HL.

  19. sir i want preamplifier of pioneer plz92

  20. Guessin’ a bit of this was lost to translation…

    “Then the signal was expanded to export the C leg of Q2 and through C5 coupling the signal to smooth out and send it to Su output gain of the circuit, which can be set from the R6/R5 C3 acts as a wizard. ”

    If I’m having difficulty procuring one, what’s an adequate substitute for a wizard…?

    1. Hello Junk McNuggets,
      Thanks for your feedback.
      I will rewrite this article.

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