Handbook for Sound Engineers

Microphones 509

source of polarizing voltage for the head, and a source
of power.
A high-quality capacitor microphone, the Sennheiser
K6 Modular Condenser Microphone Series is suitable
for recording studios, television and radio broadcast,
motion picture studios, and stage and concert hall appli-
cations, as well as high-quality commercial sound
installations.
The K6/ME62 series is a capacitor microphone
system, Fig. 16-41, that uses AF circuitry with
field-effect transistors so it has a low noise level (15 dB
per DIN IEC 651), high reliability, and lifelong stability.
Low current consumption at low voltage and phantom
circuit powering permit feeding the microphone supply
voltage via a standard two-conductor shielded audio
cable or an internal AA battery.

The K6 offers interchangeable capsules, allowing the
selection of different response characteristics from
omnidirectional to cardioid to shotgun to adapt the
microphone to various types of environments and
recording applications.
Because of the new PCM recorders, signal-to-noise
ratio (SNR) has reached a level of 90 dB, requiring
capacitor microphones to increase their SNR level to
match the recorder. The shotgun K6 series microphone,
Fig. 16-42, has an equivalent noise level of 16 dB (DIN

As in most circuitry, the input stage of a voltage

divider-type capacitor microphone has the most effect

on noise, Fig. 16-43. It is important that the voltage on

the transducer does not change. This is normally accom-

plished by controlling the input current. In the circuit of

Fig. 16-43, the voltages Vin, Vo, and VD are within 0.1%

of each other. Noise, which might come into the circuit

as Vin through the operational amplifier, is only of

the voltage Vo.

Preattenuation, that is, attenuation between the

capacitor and the amplifier, can be achieved by

connecting parallel capacitors to the input, by reducing

the input stage gain by means of capacitors in the nega-

Figure 16-41. Modular microphone system with an omnidi-
rectional cartridge utilizing a voltage divider circuit.
Courtesy Sennheiser Electronic Corporation.

Figure 16-42. The same microphone shown in Fig. 16-41

but with a shotgun cartridge. Courtesy Sennheiser Elec-

tronic Corporation.

Figure 16-43. Simplified schematic of an AKG C-460B

microphone input circuit. Courtesy AKG Acoustics.

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Vin
VD
E 1
Vout
E 2
R
D
S
G V' +
Vnoise