Here is two Low noise microphone preamplifier circuit. Which is simple circuit but high quality sound,includes devices that are selected very well.
This circuit can be used to all normal microphone, for example: the dynamic microphone of Europe zone that has impedance of about 200 ohms, the Japan microphone has impedance of about 500-600 ohms or others higher impedance microphone.
This circuit have 2 model are a balance Input Pre Microphone Amplifier circuit as Figure 1 and an Unbalance Input pre Microphone Amplifiers to can choose as you needed.
How it works
Balance Input Pre Microphone Amplifier as Figure 1. The input signal will be sent to pin 3 and pin 5 of ICs, to increase signal. And send to pin 9-10 of IC3 that act as the differential amplifier. Thus, noise signal and various hum will be rid go away.
The output from IC3 will be increased again with IC4 to get the output signal as need.
The second section, the unbalance input as Figure 2 will see that the simple circuits by have two low noise ICs to connected together as the amplifiers circuit from microphone to high amplitude as need.
How to builds
Should be used high-quality devices. For example: Metal Film Resistors, Which is a low noise.
All capacitors should be of high quality For example: polypropylene (MKP) or Polycarbonate (MKC) etc.
Parts you will need
IC1________NE5532, M5218P __OP Amp Dual General Purpose ±20 Volt 8-Pin DIP
R1_________680 ohms___1/4W Resistors tolerance: 1%
R2, R3______47K________1/4W Resistors tolerance: 1%
R4_________100 ohms___1/4W Resistors tolerance: 1%
R5, R6______1K________1/4W Resistors tolerance: 1%
R7_________8.2K______1/4W Resistors tolerance: 1%
R8_________100K______1/4W Resistors tolerance: 1%
C1_________1uF 50V __polypropylene (MKP) or Polycarbonate (MKC)
C2, C3______22pF 50V __polypropylene (MKP) or Polycarbonate (MKC)
C4_________1.5uF 50V__polypropylene (MKP) or Polycarbonate (MKC)
C5, C6______0.1uF 50V polypropylene (MKP) or Polycarbonate (MKC)
IC1__________TL074__Quad Low-Noise JFET-Input General-Purpose Operational Amplifier
R1, R4________330 ohms ___1/4W Resistors tolerance: 1%
R2, R3________22K________1/4W Resistors tolerance: 1%
R5___________1.5K________1/4W Resistors tolerance: 1%
R6, R7________6.8K________1/4W Resistors tolerance: 1%
R8, R8________1.2K________1/4W Resistors tolerance: 1%
R10, R11, R13__5.6K________1/4W Resistors tolerance: 1%
R12___________4.7K_______1/4W Resistors tolerance: 1%
R14___________100K______1/4W Resistors tolerance: 1%
C1____________22pF 50V___polypropylene (MKP) or Polycarbonate (MKC)
C2____________1.5-1.8uF 50V polypropylene (MKP) or Polycarbonate (MKC)
C3, C4_________10uF 25V___Electrolytic Capacitors
C5, C6_________0.1uF 50V__polypropylene (MKP) or Polycarbonate (MKC)
NE5532 MIC Preamp 2 channel
This be Pre Mic circuit or Microphone preamplifier circuit model 2 CH. By this circuit uses integrated number circuit NE5532 or LF353. It perform enlarge sound signal from Dynamic Micro phone give the power goes up for subsequently submit to go to still stereo power amplifier circuit next. This circuit be of good quality good sound, because of use the integrated circuit decreases the noise, but should use the fire feeds +12V GND -12V with. The VR1 and VR2 perform fine decorate the sound. The detail is other and PCB see in a picture below.
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