Construction and testing
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.
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
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