Audio Engineering

Preamplifi ers and Input Signals 229

characteristics, but the tonal preferences of the recording or broadcasting balance
engineer may differ from those of the listener.

In such a case, he might consider that the signal, as presented, was somewhat overheavy,
in respect to its bass, or alternatively, perhaps, that it was somewhat light or thin in tone,
and an adjustment of the skew of the frequency response could correct this difference in
tonal preference without signifi cantly altering the signal in other respects.

7.18.2.3 The Clapham Junction Type

This type of tone control, whose possible response curves are shown in Figure 7.54 , was
introduced by the author to provide a more versatile type of tonal adjustment than that
offered by the conventional standard systems for remedying specifi c peaks or troughs in
the frequency response, without the penalties associated with the graphic equalizer type
of control, described later.





Zb

Rin Za

R 1

R 2 Eout

C 1

0V

Figure 7.63 : Active RC treble-lift or bass-cut circuit.

Output (dB)

GainRR^1 Frequency

2 Rin

GainRR^1

in

1

2 πR 1 C 1

1

2 πR 2 C 1

f 1 f 2