Advanced Audio Microphones CM28

Advanced Audio Microphones CM28

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Advanced Audio Microphones CM28 tech. sheet

  • Manufacturer:Advanced Audio Microphones
  • Model:CM28
  • Category:Large diaphragm condenser tube microphones
  • Added in our database on:16/11/2013

Advanced Audio CM28


The Advanced Audio CM28 is a pencil microphone with a unique hybrid topology. The CM28 offers the warmth of a tube circuit combined with the detail of the Class A discrete circuits used in German condenser microphones from the 1970s. The smooth, detailed response of the CM28 makes it an excellent choice for acoustic instruments. It can also be used in high-SPL situations such as the recording of percussion.



Each CM28 microphone is supplied with cardiod, hyper-cardioid, and omni- directional capsules. A wide-cardioid capsule is available for an additional $59.


The head grill threads off to reveal a capsule similar to those used in the venerable Neumann KM84. These capsules have been designed with no grating and an extremely low rim recess in order to minimize audio reflections close to the diaphragm. The mesh head grill provides protection to the capsule that the KM84 lacked, while minimizing reflections.



The fet front end is designed to preserve all the detail captured by the 19.5mm capsule. The signal is then delivered to a 6J1b tube circuit. This sub-miniature pentode is configured as a triode to drive the BV11 transformer, an approach that takes full advantage of the low-noise characteristic of the fet circuit as well as its very fast transient response.


The tube provides the fet with a very high impedance load so the fet's headroom is maximized. The tube circuit does not need to provide any gain, so its output impedance is very low. The lower output impedance and higher output swing of the tube circuit over the fet provides greater transparency.  The tube output circuit in the CM28 can provide 6dB more headroom than the Class A transformer-coupled fet-only circuits used in the 70s German condensers.


The CM28 has a -15dB external pad for high-SPL situations, and a low-frequency switch that rolls the low end out 6dB/octave at 80hz.

A remote power supply is provided that activates the tube and the fet.




  • 19.5mm, low profile externally-polarized condenser capsule
  • Omni, Cardioid, Wide-cardiod and Hyper-cardiod pickup patterns
  • Circuit: Class A fet/tube hybrid
  • Frequency Response: 20Hz to 20kHz (response relates to pattern type)
  • Impedance: 200 ohms.
  • Max SPL: 120 dB/135dB with -15dB pad.
  • Distortion: < 1% THD @ 1KHz) 120dB, or at 135dB w/-15dB pad
  • Equivalent Noise: 18dB (A-weighted)
  • Sensitivity: 14MV/Pa = -37dB (0dB = 1v/Pa) -10dB
  • Pad: -15dB (Via Switch)
  • Filter: HPF @ 80Hz (Via Switch)
  • Weight: 4.2 oz (119 g.)
  • Size: 5 1/2" (140mm) length x 13/16" (21mm) diameter
  • Robust shock mount
  • Power Supply: 120/220VAC, 7-pin Neutrik supplying 6VDC & 125VDC
  • 7-Pin Microphone cable
  • Aluminum Road case

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