Simple Low-Noise Audio Distribution Amplifier

Petre Tzv Petrov. He was a researcher and assistant professor in Technical University of Sofia (Bulgaria) and expert-lecturer in OFPPT(Casablance), Kingdom of Morocco. Now he is working as an electronics engineer in the private sector in Bulgaria


Construction and testing

Actual-size PCB pattern of the audio-distribution low-noise amplifier
PCB pattern of the low-noise, low-cost audio distribution amplier
Fig 315
Component layout of the PCB

A single-side PCB pattern of the low-noise, low-cost audio distribution amplifier is shown in Fig. 2 and its component layout in Fig. 3.

For testing, apply well-regulated 12V power supply. First, short the input at CON1 (with no input signal) and vary VR1 till you get around half the power supply (6V) at collector of T1. Then, open the shorting input and apply a sine-wave signal around 1kHz with 10mVpp amplitude at CON1.

You can obtain a sine-wave with peak-to-peak amplitude depending on the selected gain at output pins 1, 7, 8 and 14 of A1, A2, A3 and A4 op-amps, respectively. You should get around 300 mVpp in all output pins.

Vout =(-R3/R4)×Vin


You can replace VR1 and R2 with a single resistor of around 510-kilo-ohm if the power supply is 15V and transistor T1 is BC550C.

Download PCB Component PDF: Click here

Feel interested? check out other electronics projects.


  1. Audio source like MP3 player or mobile phone can be connected at CON1. You can connect loudspeakers or audio power amplifier(s) at CON2 to CON6.


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