Audio Engineering

178 Chapter 7

Linn/Naim and Braithwaite designs, this evening out of transistor characteristics in
circuits having common base connections is achieved by the use of individual emitter
resistors to swamp such differences in device characteristics. In this case, the penalty is
that such resistors add to the base-emitter circuit impedance when the task of the design
is to reduce this.

7.6.3 Monolithic Super-Matched Input Devices

An alternative method of reducing the input circuit impedance, without the need for
separate bias systems or emitter circuit-swamping resistors, is to employ a monolithic
(integrated circuit type) device in which a multiplicity of transistors has been

1nF 47R

1K0

1000 μF

1000 μF

0.5 R

0.5 R

1K0 2N4403

2N4401

2N4401 2N4401

100 R

560 R

2N4403

2N4403

100 R

560 R

12 R

12 R 250 R

390 R

10 R

100 R

10 R

Output

390 R

M

M

Figure 7.7 : Braithwaite RAI4 head amplifi er. (The output stage is shown in a

simplifi ed form.)