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Analog Audio Frequency Generator

High-Quality Adjustable Frequency Sine Wave Generator

Analog Audio Frequency Generator
Analog Audio Frequency Generator
Last year, we published a high-quality, variable-frequency audio notch filter. To complete a typical test lab setup for measuring audio equipment performance, this article introduces a high-performance audio frequency generator with continuously adjustable output frequency control. The key component in both these designs is something called a State Variable Filter.
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Materials

Bill of Materials

Component List

Resistors

Unless otherwise specified:

MELF 0204 or thin film SMD 1206 outline, 1% tolerance

R1 = 100 Ω

R2 = 510 Ω

R3 = 150 Ω

R4, R6, R8, R12 = 2k87

R5 = 200 Ω, multi-turn upright trim pot

R7 = 2k2

R9 = 0 Ω, SMD 0603

R10, R21 = not fitted

R11, R22 = 2k2

R13 = 1k5

R14, R64 = 0 Ω

R15 = 4k22

R16 = 2k15

R17 = 1 k Linear dual gang pot 4 mm shaft

R18 = 10 k Linear dual gang pot 4 mm shaft

R19, R20, R26, R27, R44, R45 = 4k7, SMD 0603

R23, R24, R28, R29, R46…R49 = 10 k, SMD 0603

R25, R53, R56, R60…R62 = 220 Ω

R30, R31 = 1 k, SMD 0603

R32, R33 = 47 Ω, SMD 1206

R34 = 3k3

R35, R36, R40 =8k2, SMD 0603

R37 = 470 Ω, SMD 0603

R38 = 100 Ω, SMD 0603

R39 = 100 k, SMD 0603

R42 = 100 k, multi-turn upright trim pot

R43 = 27 k, SMD 0603

R50 = 2k2, SMD 0603

R51 = 5k1, SMD 0603

R52 = 10 k, linear potentiometer 4 mm shaft

R54, R55, R57…R59 = 3k3

R63 = 1k1

R65 = 4k7, hand wired*

 

Capacitors

C1, C7 = 39 n, COG, SMD 0805

C2, C8 = 100 n, COG, SMD 1206

C3, C11 = 1n2, COG, SMD 0603

C4, C12 = 33 n, COG, SMD 0805

C5, C9 = 680 p, COG, SMD 0603

C6, C10 = 15 n, COG, SMD 0603

C13, C14 = 2,200 µ / 16 V, Electrolytic 5 mm lead pitch, ø 13 mm,

C15…C18, C22…C28, C30…C32, C34, C35 = 100 n, X7R, SMD 0603

C19, C20, C33, C36…C38, C40…C43 = 22 µ / 20 V, Tantalum, SMC B

C21 = 220 µ / 16 V, Electrolytic 5 mm lead pitch, ø 10,5 mm

C44 = 3n3, X7R, SMD 0603

C45, C46 = 10 µ / 25 V, SMD 1206

C47 = 1 µ / 25 V, SMD 1206

C48 = 47 p, SMD 0603

C50 = 10 µ / 25 V, SMD 1206, hand wired*

 

Semiconductors

B1 = Bridge rectifier, B40C1000, DIL

D1…D5 = 1N4148, DO214AC

D5…D7 = SK34, DO214AC

D8, D9 = BAV199 oder BAV99, SOT23

IC1…IC3, IC9 = OPA2210, SOIC8

IC4 = 7812, TO220

IC5 = 7912, TO220

IC6 = 7805, TO220

IC7, IC8 = TL072, SOIC8

IC10 = NSL-32SR3*

LED1, LED2 = LED, SMD 0805

Q1…Q5 = 2N3904, SOT23

Q6 = 2N3904, SOT23, hand wired*

VR1 = TL431, TO92

 

Miscellaneous

F1 = PCB mounted 20 mm fuse holder 250 mA.

JP1, JP3, JP4, JP7, JP8 = 2 way pin header strip 0.1″ pitch

JP2, JP5 = 4-way pin header strip. 0.1″ pitch

JP6 = 3-way pin header strip, 0.1″ pitch

K1, K2, K3, K4 = SMD relay, 5 V, Coto Technology 9802-05-00

TR1 = PCB mounted mains transformer, 2 × 12 V / 3.6 VA, Gerth 387.24.2

X1 = 3-way terminal strip, 5 mm pitch, AK300/3

X2 = 2-way terminal strip, 5 mm pitch, AK300/2

X3, X4 = PCB mounted BNC socket, e.g., AMP 227161 BNC

2× 1-pole. 3-position switch

3× control knobs for 4 mm shaft pots

PCB

 

* see text

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