Audio Engineering

Preamplifi ers and Input Signals 185

unsuitable for high-quality audio equipment where such remote switching is employed to
minimize cross talk and hum pick up.

However, such switching devices could well offer advantages in lower quality equipment
where the cost savings is being able to locate the switching element on the printed circuit
board, at the point where it was required, might offset the device cost.

0.47μ 47 K 18 K

0.47μ 47 K 18 K

0.47μ 47 K 18 K

0.47μ 47 K 18 K

A

B

Inputs

C

D

BC414

10 K 5V





5V

5V

5V

5V

‘Off’

‘On’

0.1μ 0V

10 K

10 K

0V 0V

BC414

BC414

BC414

10 K

‘Off’

‘Off’

‘Off’

0.1μ 0V

0.1μ

0V 0V

0V 0V 0V 0.10Vμ 0V

10 K

VN10 KM

0R

0V

0V

0.1μ

0V

68 K

Output

0V

Logic level inputs

Figure 7.13 : Bipolar transistor-operated shunt switching. [Also suitable for

small-power metal–oxide–semiconductor fi eld-effect transistor

(MOSFET) devices.]