Advanced Audio CM28 Pencil Condenser Microphone

Product Description

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. The CM28 has also been lovingly used over woodwind sections at London's Angel Studios.

Each CM28 features cardioid, hyper-cardioid, and omnidirectional capsules. 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 22mm capsule. The signal is then delivered to a 6J1b tube circuit. This sub-miniature pentode is configured much like a grounded grid/triode circuit 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 6 dB more headroom than the Class A transformer-coupled FET-only circuits used in the 70s German condensers.

The CM28 has a -15 dB external pad for high-SPL situations, and a low-frequency switch that rolls the low end out 6 dB/octave at 80 Hz. A remote power supply is provided that activates the tube and the FET.