Advanced Audio CM-47 Tube Microphone

This mic has served me well over the years. Gently used in a smoke-free studio; very light patina (I struggled to get it to show in pics) but works perfectly. Original box and shock mount included.

Description:

The Advanced Audio CM47 features our very accurate and smooth AK67 capsule, a 35mm capsule with 6-micron-thick German mylar diaphragms. Its frequency response falls between those of the U47 and U67 vintage tube microphones. The AK67 capsule goes down another ½ octave before rolling out, compared to the K47 capsule. The CM47 also has more “air” or “sizzle” above 10kHz, allowing it to cut more easily through busy mixes without the addition of EQ.

Circuit:

The circuit is designed around the very HiFi 6072 tube and optimized with a two-stage Class "A" CCDA circuit. 

This circuit provides a much lower output impedance with more headroom than the original circuit used in the original U47. The lower output impedance provides a faster damping factor when driving the BV8 type transformer, delivering a better transient response than the original design.

Selected 6072a tubes are some of the quietest tubes made, and are much less susceptible to microphonics than the metal-clad vf14 tubes used in the original U47 tube microphone.

The dual-bobbin output transformer with its hum bucking configuration and our optimized circuit will deliver > +14dBu with less than 1% distortion.

The output transformer is driven with a 2.2 ufd metal-film capacitor to take advantage of the transformer’s response down below 20Hz.

Specifications:

• 1.07” (35mm) Ak67 dual back plate, dual 6-micron skinned mylar capsule Capsule polarization 60v on the back-plate.
• 9 selectable pickup patterns remotely switched from the power supply
• Dual bobbin BV8 (6.5:1 ratio) output transformer
• Selected 6072a tube Class A dual stage (CCDA)
• Frequency response: 20Hz to 20kHz +/–3dB
• Noise: <15dB (A-weighted)
• Impedance: < 200 ohm (load impedance <1.2K)
• Distortion: < 0.5% @128dB
• Maximum Output: > +14dBu with less than 1% distortion
• Robust shock mount that threads onto microphone body
• Flight case