Audio Engineering

Preamplifi ers and Input Signals 177

0.4R

47 R

270 R 270 R 270 R 270 R

680 R

3K3 3K3 3K3

3K3

Input from PU

220 R

NFB

1K0

100 μ

1000 μF 1000 μF

1 μ

6V

1000 μF 1000 μF

Output

M

Figure 7.5 : Ortofon MCA-76 head amplifi er.

270 R

0V

0V

 V

0V 0V

1nF

Input
from PU^10 μF

10 μF

47 μ

470 pF

4K7

4K7

Output

47 R

9K1

150 R

120 K

1K8

220 R

68 R

BC214

1K0

BC384 BC384 BC384 BC384 BC384

150 R 150 R 150 R 150 R

Figure 7.6 : The Naim NAC 20 moving coil head amplifi er.