Recording February 2022 - 62

REVIEW
Advanced Audio CM49LE Multi-Pattern
Tube Condenser Microphone
A subtly different flavor of the vintage tube mic sound
REVIEW BY BILL STUNT
anada's Advanced Audio has recently released an updated version
of their lauded CM49 tube microphone, the CM49LE. Company
owner and designer Dave Thomas put his estimable design skills to
the task of improving both the circuit and the look of the original Advanced
Audio model for an improved, modern and reliable offering that gets even
closer to its original inspiration, the Neumann M 49.
Introduced in 1949, the Neumann M
49 is in the exalted firmament of mics
produced at the height of the German /
Austrian microphone design era. Perhaps
slightly less known than other historic
C and M series tube mics, the M 49 is
every bit as desirable. The CM49LE is
based on the look and circuit design of a
later M 49C containing a K49 capsule,
a BV11 dual-bobbin transformer, and an
AC701 triode tube.
Birth of the cool
The original M 49 has a classic look
with its unique head basket/grille and
stubby and stocky shape. A popular
instrument and vocal mic in the 50s
and 60s, its presence is heard on many
62 RECORDING February 2022
classic recordings; it can be seen in vintage
Columbia Records session photographs
of Miles Davis and Bob Dylan.
Not available for the original CM49,
[reviewed December 2015] Advanced
Audio was subsequently able to source
a body and a standing wave-tamping
head basket that's nearly identical to the
original M 49-indeed, finding the appropriate
body was a catalyst for the redesign.
One of Dave's biggest customers
requested an 'inspirational' mic for his
musicians and singers, one that looked
and sounded like a familiar vintage microphone.
Working in an environment
with a large contingent of performers
doing Hollywood soundtrack work, the
client also wanted a very reliable mic to
minimize costly downtime.
C
A jewel in the crown
Negative feedback
The larger body offers plenty of room
to accommodate a new, full-size BV11a
dual-bobbin footprint transformer; its
10:1 ratio is specified like the original
mic. Dave also implemented additional
circuit tweaks, including a tube swap
from the first-gen CM49.
The original M 49 used a soldered
AC701 triode tube with negative feedback
to lower the tube's plate impedance.
The new Advanced Audio circuit takes a
seemingly more elegant approach; rather
than the triode 6072a in the first run
CM49, the CM49LE uses military-grade
5654w tubes strapped as triodes to lower
the plate impedance. This removes
the negative feedback requirement and
neatly eliminates two capacitors from the
circuit. Yet, it still drives the larger output
transformer with the same relative plate
impedance as the original circuit. According
to Advanced Audio, this contributes
to the mic's characteristic warmth.
The power supply has also been
tweaked with solid state regulation
to ensure that the tube's filament gets
constant voltage and the plate gets a
continuous supply.
Recording February 2022

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