3 Channel Spectrum Analyzer


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This 3 channel 15 LED spectrum analyzer is the perfect addition to any audio amp project. It produces fantastic displays on three LED bars that can be individually adjusted for any particular frequency range. The circuit will take line level output from most any audio source, and operates on 12V DC. This means that it can even be run in a car.



PartTotal Qty.DescriptionSubstitutions
R11100K 1/4W Resistor
R21820K 1/4W Resistor
R3, R14, R16, R1842.2 Meg 1/4W Resistor
R4, R5, R6322K Pot
R7, R8, R9, R25, R27, R29610K 1/4W Resistor
R10, R11, R123680 Ohm 1/4W Resistor
R13. R15, R173580K 1/4W Resistor
R19, R20, R21339K 1/4W Resistor
R22, R23, R24347K 1/4W Resistor
R26, R28, R30333 Ohm 1/4W Resistor
C1, C5, C630.012uF Polystyrene Capacitor
C2, C9, C10, C1143.3uF Electrolytic Capacitor
C3, C420.0022uF Polystyrene Capacitor
C7, C8247nF Polystyrene Capacitor
C12, C13, C1430.47uF Electrolytic Capacitor
C15, C16, C17322uF Electrolytic Capacitor
D1, D2, D331N4002 Silicon Diode
D4, D5, D6, D8, D85Green LED
D10, D11, D12, D13, D145Amber LED
D16, D17, D18, D19, D205Red LED
U11LM3900 Quad Op Amp
U2, U3, U43AN6884 Bar Graph IC
MISC1Board, Wires, Sockets For ICs


1. The circuit expects line level inputs. If you connect it to speaker level, you will have to readjust the circuit every time you change the volume.
2. After the circuit is connected, apply power and signal. Now adjust the pots until the corresponding group of LEDs reacts.