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Article

Attenuators for Audio Signals (2)

Switching Via Relays

Attenuators for Audio Signals (2)
Attenuators for Audio Signals (2)
The first article in this series presented a simple passive attenuator whose stages can be set using a jumper. Such a solution is well-suited for a simple standalone device if you don’t need it that often. However, if you want to install such an attenuator somewhere permanently, the stages should be selectable with a changeover switch. This is exactly what the two circuits in this second part do.
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Materials

Component list

Component List for SE Relay Version

Resistors:

Unless otherwise specified:

MELF 0204 or thin-film SMD 1206, 1%

R1…R13 = 10 kΩ

R14 = 1 kΩ

R15, R17, R19, R21, R23 = 4.7 kΩ, SMD 0603

R16, R18, R20, R22, R24 = 10 kΩ, SMD 0603

 

Capacitors:

C21, C22 = 100 nF, SMD 0603

 

Semiconductors:

D1…D5 = 1N4148, DO214AC

D6 = BAV199, SOT23

T1…T5 = 2N3904, SOT23

 

Miscellaneous:

JP1, JP2, JP4 = 2-pin header, 1/10″ pitch

JP5 = 3-pin header, 1/10″ pitch

JP3 = 6-pin header, 1/10″ pitch

Rel1…Rel5 = relay, 5 V, type 9802-05-00

Component List for Diff/Stereo Relay Version

Resistors

Unless otherwise specified:

MELF 0204 or thin-film SMD 1206, 1%

R1…R13, R25…R37 = 10 kΩ

R14, R38 = 1 kΩ

R49…R52 = 0 Ω, SMD 0603, see text

R15, R17, R19, R21, R23, R39, R41, R43, R45, R47 = 4.7 kΩ, SMD 0603

R16, R18, R20, R22, R24, R40, R42, R44, R46, R48 = 10 kΩ, SMD 0603

 

Capacitors

C21, C22 = 100 nF, SMD 0603

 

Semiconductors

D1…D12= 1N4148, DO214AC

D6, D7 = BAV199, SOT23

T1…T10 = 2N3904, SOT23

 

Miscellaneous

JP1, JP2 = 4-pin header, 1/10″ pitch

JP3 = 6-pin header, 1/10″ pitch

JP4 = 2-pin header, 1/10″ pitch

JP5 = 3-pin header, 1/10″ pitch

Rel1…Rel10 = relay, 5 V, type 9802-05-00

Circuit board 240176-03

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