LM1036 datasheet(6/10 Pages) NSC

6 / 10 page

Applications Information (Continued)

Figure 4 shows the effect of changing C

t and Cb in the oppo-

site direction to C

t/2, 2Cb respectively giving reduced control

ranges. The various results corresponding to the different C

and C

b values may be mixed if it is required to give a particu-

lar emphasis to, for example, the bass control. The particular

case with C

b/2, Ct is illustrated in Figure 5.

Restriction of Tone Control Action at High or Low

Frequencies

It may be desired in some applications to level off the tone

responses above or below certain frequencies for example

to reduce high frequence noise.

This may be achieved for the treble response by including a

resistor in series with C

t. The treble boost and cut will be 3

dB less than the standard circuit when R=X

A similar effect may be obtained for the bass response by re-

ducing the value of the AC bypass capacitors on pins 5

(channel 1) and 16 (channel 2). The internal resistance at

these pins is 1.3 k

Ω and the bass boost/cut will be approxi-

mately 3 dB less with X

C at this value. An example of such

modified response curves is shown in

Figure 6. The input

coupling capacitors may also modify the low frequency re-

sponse.

It will be seen from

Figure 2 and Figure 3 that modifying C

and C

b for greater control range also has the effect of flatten-

ing the tone control extremes and this may be utilized, with

or without additional modification as outlined above, for the

most suitable tone control range and response shape.

Other Advantages of DC Controls

The DC controls make the addition of other features easy to

arrange. For example, the negative-going peaks of the out-

put amplifiers may be detected below a certain level, and

used to bias back the bass control from a high boost condi-

tion, to prevent overloading the speaker with low frequency

components.

LOUDNESS CONTROL

The loudness control is achieved through control of the tone

sections by the voltage applied to pin 7; therefore, the tone

and loudness functions are not independent. There is nor-

mally 1 dB more bass than treble boost (40 Hz–16 kHz) with

loudness control in the standard circuit. If a greater differ-

ence is desired, it is necessary to introduce an offset by

means of C

t or Cb or by changing the nominal control voltage

ranges.

Figure 7 shows the typical loudness curves obtained in the

standard application circuit at various volume levels

b=0.39 µF).

Figure 8 and Figure 9 illustrate the loudness characteristics

obtained with C

b changed to Cb/2 and Cb/4 respectively, Ct

DS005142-7

FIGURE 4. Tone Characteristic (Gain vs Frequency)

DS005142-8

FIGURE 5. Tone Characteristic (Gain vs Frequency)

DS005142-9

FIGURE 6. Tone Characteristic (Gain vs Frequency)

DS005142-10

FIGURE 7. Loudness Compensated Volume

Characteristic

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