Advanced Audio Microphones CM251

• Fabricant : Advanced Audio Microphones
• Modèle : CM251
• Catégorie : Micros statiques à tube à large membrane
• Fiche créée le : 22/04/2015

Summary
The Advanced Audio CM251 is a large-format condenser tube microphone based on the famous ELA M251. Like the original ELA M251 it is an outstanding choice for vocals. Historically, the original was used on countless hit records and recordings, including Joni Mitchell and Frank Sinatra. Advanced Audio’s CM251 emulates the smooth and present character of the original, while staying true to our own circuit designs by not simply designing a clone. 

Capsule
The CM251 features Advanced Audio’s own AK12 capsule, an edge-fed, dual diaphragm capsule skinned with 6 micron German mylar that has a frequency response matching within ±2dB the response of the AKG CK12 capsule. The capsules are hand-picked and tested in our shop to insure both sides are within 2pfD.

Circuit 
The CM251’s circuit has been designed around the 6072a dual triode, hand selected,  tube. The unused half of the 6072a is incorporated as a cathode follower, resulting in a much lower output impedance than that of the original circuit. This lower output impedance improves the damping factor and allows the use of a transformer with half the turns-ratio of the original ELA M251. The result is a circuit with more headroom than the original plate fed circuit with a better low frequency and high frequency response. The open top end sound of the mic is smoothed out with the use of a capacitor rolling off some of the high end. The result is a 3dB drop at 10k.

Output
The CM251 utilizes a BV18 dual-bobbin output transformer. Wound to the original specs, it is easily driven by the optimized low-impedance 6027a circuit, yielding 6db more output level than the original transformers used in the AKG C12 and ELAM 251. This allows the head amp gain to be further reduced, increasing the total headroom (output level before distortion) by 6dbB.
The BV18 transformer is driven through a 2.2-ufd mylar capacitor to take advantage of the ability of both capsule and transformer to respond to frequencies reaching down to 10Hz. The transformer can deliver +18dBm with less than 1% distortion across the audio spectrum.

Specifications:

• Dual diaphragm, dual back-plate, 35mm edge fed AKG type capsule with 6-micron mylar. 
• Class A 6072a tube circuit
• BV18 output transformer

• Frequency response: 15Hz to 20kHz 
• Noise: -17dB (A-weighted) 
• Impedance: <200 ohms 
• Distortion: 0.5% @ 125dB
• Output: +18dBm @<1% distortion into 1.2K ohms.

• Robust shock mount 


• Aluminum road case 
• 25’ 7 gold pin cable
• 9 selectable pick-up patterns switch from the included power supply.