Dynamic Microphone Preamplifier circuit using C945

If friends are looking Dynamic Microphone Preamplifier circuit is high quality. So the low noise signal. I suggest this circuit because It use the three transistor (2SC945, or 2C1815 or 2SC828) is main Which typical transistor amplifier with a low noise this circuit, too. There are about 200-300 times the gain. The frequency response is 50Hz to 100KHz.
This circuit use the 12 volts – 24 volts DC power supply.
An they is designed for use with 200 Ohm dynamic microphones. For usage with low impedance microphones.
You can see the project Dynamic Microphone Preamplifier using C945 transistor 2 vertion and easy to build with pcb layout see below.

Circuit of Pre MIC – 3 Transister (C945) mono

PCB of Pre MIC – 3 Transister (C945) mono

The second circuit.


Using BC547 transistors

This is a simple microphone preamplifier circuit that use 2 transistors are connected in the direct coupling, to respond the signal even better.

How it works
In Figure 1 the circuit diagram
the circuit diagram

On collector of Q2 will feedback signal to the emitter of Q1, To frequency response is improved.

And,at the same time R1 will connect voltage from the emitter of Q2, to bias Q1.

The input signal into C1 to amplifier by Q1,Q2 and then there are the output signal at collector of Q2 through capacitor-C6 to a power amplifier.

The power supply of the circuit, we may use simple circuit as shown in block dash include Full wave rectifier D1,D2 and capacitor filter C7.

But someone want the high quality power supply should use 12V dc regulator.

The parts you need.
Q1-Q2______.BC548.BC547.BC549____45V 100mA NPN Transistor
R1_________390K___0.25W tolerance: 5%
R2________680 ohms___0.25W___”____
R4,R5_____ 220K_______0.25W___”____
R6________ 10K________0.25W___”____
R7_________ 1K________0.25W___”____
C1________1uF 50V Electrolyte Capacitors
C2,C4_____4.7uF 16V ___”________”____
C3________100pF 50V__”________”____

How to builds
Figure 2 is Actual-size of Single-sided Copper PCB layout and Components layout of this projects.
Actual-size of Single-sided Copper PCB layout and Components layout

Pre MIC mono using 2 Transistor C945

This is low noise microphone preamplifier circuit, by 2 Transistor mono part name C945 or C828 or 2SC829 or C458.
The supply volt is 12V – 24V. Easy to build and low cost.
I have an old microphone,I want to make play with common amplifier. It does not sound much. Must to use pre amp before.I search a lot of circuits, see this circuits it very well for me,low cost, use transistor.

Pre MIC mono by 2 Transistor C945
Circuit of Pre MIC mono by 2 Transistor C945

PCB of Pre MIC mono by 2 Transistor C945


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Verry good but how can i use c945 in an emetteur fm?

Dwi Sugiarto

This circuit what I look for very useful for me,Thanks


how i can made radio with this circuits


this circuit is verry good, thanks for your post.
how to make the output is stereo?

Robert Smith

Hello and thanks for this information, Id like to build the first circuit on this page, I’m having a problem reading “PCB of Pre MIC – 3 Transister (C945) mono” I cant see a clear guide… It is obscured by the black ink, please…. pretty please change the photo…. or… could you email me a copy of it?


i need completereport for this

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