Detail changes continue to be made to the AEA 44 series as AEA gains more experience. The most dra-
matic technical revision was changing the internal wiring from the top of the ribbon to the transformer
input leads. Examination of the RCA 44 production from England revealed that their wiring scheme
reduced hum sensitivity by 20 dB without altering the sound. This wiring was immediately adopted for
all R44 microphones. More recently the yoke material casting on the R44C was changed from zinc to
bronze. The original RCA zinc yokes were found to fail when the plating wears through and the zinc
is exposed to moisture. More recently the R44C cushion-mount cable-clamps were changed from cast
zinc to machined brass.
Recalling Olson’s prediction that a well designed ribbon microphone might have the lowest self-noise
of any microphone type, AEA next focused its attention on lowering the noise and extending the linear-
ity of the ribbon microphone / microphone preamplifier interface. The 2005 AEA model TRP ribbon
microphone preamplifier was designed specifically to deliver high gain while reducing noise and in-
creasing linearity. This JFET design has a low noise floor, is DC coupled for wide bandwidth, and has
a no load, ultra-high input impedance design that delivers exceptional frequency response linearity and
better signal to noise with ribbon microphones.
Following on the widespread acclaim for the TRP, the next logical step was to incorporate similar
circuitry inside the microphone itself. The AEA model A-440 debuted at the NAB Show in April 2008.
Its internal phantom-powered JFET buffer amplifier is combined with a new, higher-ratio transformer
to provide 12 dB more gain than the ‘X’ motor alone. The equivalent acoustic self-noise of the combi-
nation is 9 dB (A) or less – making it among the quietest microphones made. Although the acoustic fre-
quency response of an A440 is the same as an R44CX, the sonic character is different. This character is
often described as “warmer” or “more tube-like.” and the bass is reported as having more weight.
Placing a buffer amplifier inside the A440 radically reduces the distance between the ribbon step-up
transformer and the first electronics stage. This decreases mic-line noise interference. It also buffers
the microphone preamp from possible low frequency EQ effects as a ribbon’s output impedance rises
at resonance. The A440’s audio-band output impedance is a constant 92 ohms for flatter low frequency
response when driving typical microphone preamps.
The trade off with such an active studio ribbon designs is a reduction of the 165 dB SPL capabilities
of the AEA’s passive R series ribbon microphones. While microphone positions that exceed 135 dB SP
are rare two examples are extremely close horn and percussion microphone positions pickup . Under
such circumstances, moving the microphone back three to six inches can solve the problem.
The A440 has the ability to drive a 1,000 ohm load at SPLs up to 135 dB and a high sensitivity of -33.5
dBV at 94 dB SPL (30 mV/Pa). The A440 matches conventional microphone preamplifiers quite well.
The A440 draws 7 mA of P48 phantom power. This amount of current allows it to achieve a noise floor
of 9 dB (A) or less with a headroom limit of 135 dB SPL.
Knowledgeable engineers never stopped using the 44. In the mid 1960s remote recording pioneer Wal-
ly Heider always used RCA ribbons on big bands and horn sections. Capitol Records Studios maintains
a large collection of 44s and has used them continuously on projects since the 1940s. Performers such
as Bing Crosby owned their own personal 44s. Young Frank Sinatra’s use of a 44 in live performances
was brilliant. He understood how to work the 44 to change his sound dynamically during a song and
increase its dramatic impact.
