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The Sony Models C-55FET and C-55P
cardioid condenser microphones – 1970

Sony C-55P
The original C-55 above is battery-powered, and uses a DC-DC converter to pro­vide polarization voltage to the condenser microphone capsule. The C-55P FET microphone omits the DC-DC converter, and polarizes the microphone capsule from the P48 powering. (An image of the Model C-55P FET can be seen below.)

General Description
The Sony Model C-55P is a lightweight handy type uni-directional condenser microphone intended for broadcast or recording studio use, with features as follows.

  • Phantom Powering System
    The microphone is operated from an AC power source by using Sony AC Adapter AC-148A (optional). The shielded two-conductor microphone cable is used as both an audio signal cable and a DC power supply cable by connecting to the AC-148A. Positive DC current is supplied to the microphone through the inner two conductors of the cable, and negative DC current through the shield conductor.

Figure 1-1

  • Low-Cut Switch
    This switch has the following three positions: M for a flat frequency response, M1 for slight attenuation of low frequen­cies, and V1 for extreme attenuation of low frequencies.

Figure 1-2

  • High-Cut Switch
    This switch has the following two positions: Flat frequency response, and Attenuation in the frequency range higher than 5 kHz.

Figure 1-3

  • Pad Switch
    This switch has the following two positions: 0 for no atten­uation, and -8 dB for eight decibels of attenuation over the entire frequency range, used for high-pressure sound pick-up.

Figure 1-4

  • Capsule Angle Change
    The capsule angle can be changed through 90 degrees vertically by pressing the two side buttons.

Figure 1-5

Sony C-55P
Photo courtesy of Rick Chinn

Sony C-55P
The Model C-55P FET microphone shown here has its rolloff selector ring in a different location from that of the Model C-55 seen at the top of this page, and does not have the “BATT” nor “OFF” switch positions. Images and a description of a P48 power supply designed and built by Rick Chinn can be viewed here. Use your “Back” button to return to this page after you view Rick’s work.

Type: C-55P FET condenser microphone

Power Supply: Standard operating voltage; DC 48–54 V
              Current Drain: Less than 2.5 mA

Frequency Response: 40–16,000 Hz ±2.5 dB

Output Level:
Pad switch Output     Effective      Open circuit  EIA
position   impedance  output level   output level  rating GM
                        *(dBm)         **(dB)        ***(dB)
—————————  —————————  ————————————  —————————————  —————————    0         250 Ω      –49.8       –50 (3.16 mV)   –141.8
  –8 dB      250 Ω      –57.8       –58 (1.25 mV)   –149.8

                  *0 dBm = 1 mW/10 µbar, 1,000 Hz
                 **0 dB  = 1 V/10 µbar, 1,000 Hz
                ***EIA standard SE–105

Directivity: Uni-directional

Output Impedance: 250 Ω ±20% at 1,000 Hz balanced

Noise Level: S/N ratio: more than 50 dB (1,000 Hz, 1 µbar)
             Inherent noise: less than 24 dB-SPL
             Wind noise† less than 43 dB-SPL
             Induction noise of external magnetic field‡
             less than 5 dB-SPL/milligauss
†The value measured by applying a wind of 6.6 feet/second
 velocity from all directions to the microphone. The mean
 value is taken and converted to the equivalent input sound
            (0 dB = 2 × 10-4 µbar)

‡The external magnetic field induction noise is measured with
 the microphone placed in the alternating magnetic field of
 50 Hz, 1 milligauss. The maximum noise value is taken and
 then converted to the equivalent input sound level:
            (0 dB = 2 × 10-4 µbar)
Maximum Input Sound Pressure Level: 154 dB-SPL. This is the maximum input level which produces less than 1% wave distortion at the output with 1,000 Hz, and less than 1% intermodulation distortion at the output signal with 70 Hz to 7 kHz

Dynamic Range: 130 dB (0 dB = 2 × 10-4 µbar)

Semiconductors: 1 module, 1 transistor

Dimensions: 1.3 inch diameter × 6.56 inches length
            (33 mm diameter × 167 mm length)

Weight: 10 ounces (280 g) without cable

Sony C-55P


Numerous technical illustrations, including some not shown here, can be found in the three booklets that are available for down­loading from the bottom of this page.

Sony C-55P

FET cover
Download the C-55FET Operating Instructions.
Special thanks to Rick Chinn for this manual.

C-55P cover
Download the C-55P Operating Instructions.
Special thanks to Jim Zuehsow for this manual.

Service Manual
Download the C-55P Service Manual.
Special thanks to Ms. Kimberly Stewart
of Sony Corporation for this manual.



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