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.
Vout =(-R3/R4)×Vin
=30×10mVpp=300mVpp
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:Â Click here
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can you please tell me what is the difference between Simple Audio Amplifier and Audio-Distribution Amplifier?
which types of audio devices should be used in con1,2,3,4,5,6?
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.
can you explain how to test input and out
What’s difference between this circuit & the headphone buffer circuit project by same author? Can both the circuits be used to connect multiple headphones?