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Three Channel Spectrum Analyzer

Here is a simple analog circuit from Electronic Circuits that provides a visual, bar graph Spectrum Analyzer for audio frequencies:

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.

Schematic


Schematic for amp

Parts:
 

Part

Total Qty.

Description

Substitutions

R1

1

100K 1/4W Resistor

 

R2

1

820K 1/4W Resistor

 

R3, R14, R16, R18

4

2.2 Meg 1/4W Resistor

 

R4, R5, R6

3

22K Pot

 

R7, R8, R9, R25, R27, R29

6

10K 1/4W Resistor

 

R10, R11, R12

3

680 Ohm 1/4W Resistor

 

R13. R15, R17

3

580K 1/4W Resistor

 

R19, R20, R21

3

39K 1/4W Resistor

 

R22, R23, R24

3

47K 1/4W Resistor

 

R26, R28, R30

3

33 Ohm 1/4W Resistor

 

C1, C5, C6

3

0.012uF Polystyrene Capacitor

 

C2, C9, C10, C11

4

3.3uF Electrolytic Capacitor

 

C3, C4

2

0.0022uF Polystyrene Capacitor

 

C7, C8

2

47nF Polystyrene Capacitor

 

C12, C13, C14

3

0.47uF Electrolytic Capacitor

 

C15, C16, C17

3

22uF Electrolytic Capacitor

 

D1, D2, D3

3

1N4002 Silicon Diode

 

D4, D5, D6, D8, D8

5

Green LED

 

D10, D11, D12, D13, D14

5

Amber LED

 

D16, D17, D18, D19, D20

5

Red LED

 

U1

1

LM3900 Quad Op Amp

 

U2, U3, U4

3

AN6884 Bar Graph IC

 

MISC

1

Board, Wires, Sockets For ICs

 

 

Notes:

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.

Niccola 2010-10-21 01:20:00
What is the value of C18??

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