Audio Engineering

172 Chapter 7

The circuit arrangements shown in Figures 7.4(c) and 7.4(d) use “ shunt ” type negative
feedback (i.e., that type in which the negative feedback signal is applied to the amplifi er
in parallel with the input signal) connected around an internal gain block.

These layouts do not suffer from the same limitations with respect to source or load as
the simple passive equalization systems of Figures 7.4(a) and 7.4(b). However, they do
have the practical snag that the value of Rin will be determined by the required PU input
load resistor (usually 47k for a typical moving magnet or variable reluctance type of PU

Figure 7.4 : Circuit layouts that will generate the type of frequency response required for

RIAA input equalization.

In R 1 Out

R 2

C 1

C 2

(a)

R 2 C 2

C 1

In R 1 Out

(b)

Rin R^1

R 2

C 2

C 1

PU

(c)

0V

Out





R 2

Rin

Out

R 1

C 1

C 2

PU 

0V

(d)

Rin R 2

R 1

R 3

RFB

CFB

C 1

C 3

0V

C 2





PU

(e)

R 2

Rin

Out

0V

RFB

CFB

C (^1) C
C^3
2

PU
(f)
R 1
R 3 R 3
R 2
(g)
0V
Rin
R 1
RFB C^3
CFB
PU G