Audio Engineering

Recording Consoles 783

transformer itself provides some voltage gain at the expense of presenting a much higher
output impedance to the following amplifi er. However, the amplifi er has an extremely
high input impedance (especially so when negative feedback is applied) so this is really
of no consequence. In Figure 27.14 , amplifi er gain is made variable so as to permit the
use of a wide range of microphone sensitivities and applications. An ancillary circuit is
also provided that enables the signal entering the circuit to be attenuated by 20 dB, which
allows for very high output microphones without overloading the electronics.

Signal input

Signal

source

Phantom

power

Connecting

balanced-line

48V

Figure 27.15 : Transformer-based input stage.