The Altec Models 632C, 633A/C
moving coil dynamic microphones

Additional documentation on these mics is available.

632C Specifications

• Type:  Moving Coil Dynamic
  
  
• Frequency Response:  100 to 10,000 cycles
  
  
• Output Impedance:  30/50 ohms
  
  
• Output Level:  −55 dBm/10 dynes/cm²
  
  
• Dimensions:  2¹⁄₈ inches long, 2 inches diameter
  
  
• Weight:  8¼ ounces
  
  
• Finish:  Instrument gray
  
  
• Mounting:  ⁵⁄₈''-24 thread
  
  

633A/C Specifications

• Type:  Moving Coil Dynamic
  
  
• Frequency Response:  35 to 12,000 cycles
  
  
• Output Impedance:  633A—30/50 ohms, 633C—30/50, 150/250 ohms (selectable)
  
  
• Output Level:  −55 dBm/10 dynes/cm²
  
  
• Dimensions:  3½ inches long, 2 inches diameter
  
  
• Weight:  633A—10 ounces, 633C—13 ounces
  
  
• Finish:  Instrument gray
  
  
• Mounting:  ⁵⁄₈''-24 thread

IMPEDANCE SELECTION AND CONNECTIONS

632C and 633A Microphones
The 632C and 633A Dynamic Microphones are single impedance microphones. The impedance is 30/50 ohms. Located on the bottom plate (Figure 1) are three terminals. Terminal number one is the common terminal. Terminal number two is the hot or positive side of the microphone. Terminal G is ground for use with a balanced system. The 632C comes with two yellow leads connected to terminals one and two. To connect the microphone to an unbalanced line, connect terminals one and G together.

633C Microphone
The 633C Dynamic Microphone is a dual-impedance microphone. The two imped­ances are 30/50 ohms and 150/250 ohms. For selection of 30/50 ohms (Figure 2), connect the terminal marked 30-50 to the hot or positive side of the audio cable. Connect the common lead to the Terminal marked 0. For connection of the 150/150 ohm side of the microphone (Figure 3), connect the hot or positive side of the audio cable to the terminal marked 150-250 and the common lead to the terminal marked 0. If an unbalanced line is required, connect terminals G and 0 together.

Text and illustrations are from the Altec Lansing 632C, 633A/C Operating Instructions,
Altec Lansing Publication No. 40465−1, Copyright © March, 1966. Downloadable below.

All photographs are via the courtesy of Ellis Dawson.

Download the 632C, 633A/C instruction sheet.