Tone Control Circuit (Active and passive)

Among the most popular control circuit found in an audio system is tone control. The tone control is used to modify the tonal characteristic of the signal chain i.e. it enables the listener to alter the tonal quality of the sound being reproduced. The effect of tone control has on the frequency response of the equipment and their purpose is to help remedy shortcomings in the source program material, the receiver or transducer, or in the loudspeaker and the listening room combination.

These are either of the passive types, of which a typical circuit layout is shown in Fig. 1, or are constructed as part of the negative feedback loop around a gain block, using the general design due to Baxandall. Typical circuit layouts for active tone control are shown in Figs. 2-5.

passive tone control

PARTS LIST FOR FIG.1 PASSIVE TONE CONTROL

Resistor (all ¼-watt, ± 5% Carbon)
R1 = 15 KΩ

R2 = 2.2 KΩ

R3 = 22 KΩ

VR1, VR2 = 100 KΩ

Capacitors
C1, C6 = 10 µF/12V (Electrolytic Capacitor)

C2 = 0.022 µF

C3 = 0.22 µF

C4 = 0.001 µF

C5 = 0.01 µF

 

active tone control using single transitor

PARTS LIST FOR FIG.2 ACTIVE TONE CONTROL USING SINGLE TRANSISTOR

Resistor (all ¼-watt, ± 5% Carbon)
R1, R2, R4 = 10 KΩ

R3 = 5.6 KΩ

R5 = 220 KΩ

R6 = 33 KΩ

R7 = 4.7 KΩ

R8 = 1 KΩ

VR1, VR2 = 100 KΩ

Capacitors
C1, C5, C7, C9 = 10 µF/12V (Electrolytic Capacitor)

C2, C6 = 0.0033 µF (Ceramic Disc)

C3, C4 = 0.033 µF (Ceramic Disc)

C8 = 47 µF/6V (Electrolytic Capacitor)

Semiconductor
T1 = BC148

 

active tone control using LM387

PARTS LIST FOR FIG.3 ACTIVE TONE CONTROL USING LM387

Resistor (all ¼-watt, ± 5% Carbon)
R1 – R4 = 10 KΩ

R5 = 680 Ω

R6 = 180 KΩ

R7 = 1 MΩ

VR1, VR2 = 100 KΩ

Capacitors
C1, C7, C10 = 10 µF/12V (Electrolytic Capacitor)

C2, C5 = 0.0033 µF (Ceramic Disc)

C3, C4, C6 = 0.033 µF (Ceramic Disc)

C8, C9 = 0.1 µF (Ceramic Disc)

Semiconductor
IC1 = LM 387

 

active tone control using LM349

PARTS LIST FOR FIG.4 ACTIVE TONE CONTROL USING LM349

Resistor (all ¼-watt, ± 5% Carbon)
R1 – R4 = 10 KΩ

R5 = 1 KΩ

VR1, VR2 = 100 KΩ

Capacitors
C1, C4 = 0.0033 µF (Ceramic Disc)

C2, C3, C5 = 0.033 µF (Ceramic Disc)

C6, C7 = 0.1 µF (Ceramic Disc)

Semiconductor
IC1 = LM 349

 

active tone control using LM741 or LM348

PARTS LIST FOR FIG.5 ACTIVE TONE CONTROL USING LM741 OR LM348

Resistor (all ¼-watt, ± 5% Carbon)
R1, R3 = 10 KΩ

R2, R4, R5 = 15 KΩ

VR1, VR2 = 100 KΩ

Capacitors
C1 = 0.047 µF (Ceramic Disc)

C2 = 1 Kpf (Ceramic Disc)

C3, C4 = 0.1 µF (Ceramic Disc)

Semiconductor
IC1 = LM 741 OR LM 348

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