low noise audio preamplifier circuit schematic

Low Noise Audio Preamplifier Circuit

A preamplifier circuit with a very low noise characteristic can be built by simply combining a FET transistor with a bipolar one.
The input impedance of the preamp circuit is almost the same as the gate impedance of the FET transistor (around 1MΩ) The output impedance at the other end is about 1KΩ.
The frequency of this preamplifier is linear (-3dB) between 10 Hz and 450 kHz and -1dB between 20 Hz and 200 kHz. The amplifying factor is aroung 100.

This preamp circuit can be powered from 12 to 30 volts without significant deterioration in its amplifying characteristics

Low noise preamplifier circuit diagram

low noise audio preamplifier circuit schematic

Low noise preamp printed circuit board


Active components

  • T1 = 2N3819, 2N3823
  • T2 = 2SA1515, 2SB822, 2SB909, 2SB911



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  • wildee44yahoo-com

    Just found out that c1 is 0.47 micro farads and r5 is 82 ohms. Yay me.

  • wildee44yahoo-com

    What is the value of c1 and r5 and why are there no replays to questions here?

  • Arturo Esparza

    I forgot to mention: I am having trouble to decide what type of preamp I need. The schematics I have seen say: “phono”,tape” cassette”,guitar,microphone,but for the sound card on a computer (the output,or outline) what should I use?
    I am using the “auxiliary” input of my Amplifier to amplify the computer sound…and it gives me a reasonable good sound…the advantage of listening music there(the computer),is that you have Hugh saving capacity and you can choose the software you prefer,like winamp,media player,or even watch movies with your preferred amplifier.Great control, great storage,Big sound… you know what I mean? thanks in advance
    Thanks in advance.

  • Pasaway

    Hi, I’m working on a school project. And I’m planning to use this preamp circuit diagram. What’s the value of C1? For T1 and T2 do I just choose one from the list? Would it all work for 12V power supply? and can you suggest an amplifier circuit that would work with this preamp?

    Thank you in advance.

  • tamsil

    sangat berguna(useful).tolong dibuatkan mic compressor,bila tidak dimodulir, huming backgroung sangat terdengar, bila dimodulir, backgroung tidak terdengar(clean). semacam kenwood mc85.

    terima kasih sebelumnya

  • mozikluv

    hi, i have designed such a circuit way back in 2006 for a friend.



  • john

    nyc job men!!!salamat ha…

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