Audio Engineering

Preamplifi ers and Input Signals 223

7.18.2.1 Standard Tone Control Systems

These are either of the passive type, of which a typical circuit layout is shown in Figure
7.57 , or are constructed as part of the negative feedback loop around a gain block using
the general design due to Baxandall. A typical circuit layout for this kind of design is
shown in Figure 7.58.

It is claimed that the passive layout has an advantage in quality over the active (feedback
network) type of control in that the passive network merely contains resistors and

30 100

 10

0

 10

1 K 10 K 20 kHz

Frequency

Gain (dB)

Figure 7.53 : Slope control.

 12

 9

 6

 3

 3

 6

 9

 12

0

25 50 100 200

Gain (dB)

400

Frequency

1.5 K 3 K 7 K 14 K 20 kHz

Figure 7.54 : Clapham junction type of tone control.