Last Updated on November 7, 2023 by AG
Regarded by many as the pinnacle of audio capture devices, the Neumann U47 has long secured its spot in the annals of sound recording history. This iconic microphone, which came into existence in the post-World War II era, continues to be a sought-after piece of equipment, celebrated by music enthusiasts and professionals alike.
The Neumann U47 represents a brilliant intersection of technical innovation and artistry, contributing its unique sound to countless classic recordings, and capturing the voices of some of the world’s most iconic singers.
The Beatles and Frank Sinatra, among others, leveraged its capabilities to astounding effect. Its influence has permeated across genres and generations, from jazz’s sultry notes embodied by Ella Fitzgerald, to the soul-stirring ballads of Adele, the folksy tunes of the Kingston Trio, and even the timeless pop anthems of Michael Jackson.
The key to the U47’s distinctive sound is the VF14 tube, a pentode tube that Telefunken specially developed for this microphone. In tandem with the legendary M7 capsule, the VF14 tube helped to create a warm, full-bodied sound that artists and producers fell in love with. Whether used for vocals, drum recording, or virtually any instrument, the U47 delivers an authentic, musical, and “big” audio experience.
The Best Microphone of All Time: Why the U47?
To label any piece of equipment as “the best” is often a contentious point, given the subjective nature of such judgments. However, the Neumann U47 seems to stand the test of time and critics, consistently ranking at the top of lists of the finest microphones. But what sets the U47 apart?
Firstly, the U47 has an unparalleled track record in music production. The timeless quality of its sound profile has graced countless iconic recordings, making it a favorite amongst legendary artists and producers. This microphone’s unique ability to capture an artist’s performance in a natural and expansive manner has been a defining characteristic that has yet to be matched.
Moreover, the U47 is treasured for its sonic versatility. It’s equally at home capturing the intimate nuances of a solo vocalist as it is dealing with the powerful hits of a drum kit. Regardless of the sound source, the U47 seems to add a magical touch, enhancing the audio with its signature warmth and depth.
Unveiling the Neumann U 47: Ingenious Design and History
As the first microphone produced by Georg Neumann GmbH in post-war Berlin, it set new industry standards, making its mark in the early 1950s and beyond.
When Georg Neumann launched the U47 in 1949, he did not merely introduce a new product to the market; he unveiled a masterpiece that would revolutionize the realm of sound recording. The U47 became the first switchable pattern condenser microphone, capable of switching between a cardioid and omnidirectional mode, a feature that provided unprecedented versatility to sound engineers and producers.
Its debut took place at the Berlin Radio Show in 1947, giving birth to the model number 47. However, production commencement was delayed until 1949. The microphone’s distinguishing ‘U’ label indicates the utilization of a plug-in style amplifier tube, in this case, the renowned VF14.
Audio engineers like Rudy van Gelder, who got the second-ever U 47 to reach the States, instantly appreciated the U 47’s sensitive nature. They noticed its ability to lend a heightened sense of presence and detail to their recordings. This microphone’s unique character played a significant role in shaping the fantastic sound of Gelder’s early Blue Note work, as any aficionado will readily attest.
However, superior audio quality comes at a premium. Originally, the U 47 cost three times as much as the RCA 77 ribbon mic, the second most expensive microphone of the time.
The fusion of the head grille, diaphragm, tube, and output transformer engendered an enchanting tone that remains unmatched to this day. Each individual element contributes to this amazing transducer, leaving an indelible imprint on every recording.
In the aftermath of World War II, Germany lacked standardized electrical current supplies or voltages, and dual-tube radios with 110v (AC or DC) were commonplace. For practical purposes, consumer radios were designed to use two tubes in series, each drawing 55 volts directly from the main power.
In response to broadcasters facing similar dilemmas, Neumann designed microphones that could function directly from main supply when necessary. The ubiquitous VF14 tube, manufactured in Berlin, was adopted to power these microphones. This strategic decision has had historical implications for both the tone of the microphones and their continued desirability decades later.
The Inner Workings of the U47: The VF14 Tube and the M7 Capsule
The essence of the Neumann U 47 is the VF14 tube. Crafted by Telefunken, the VF14 is a steel-encased pentode tube, with various styles created, but alas, none matching the unique specifications of the original VF14. In an exchange that circumvented patent royalty payments, Neumann granted Telefunken the distribution rights (and badging) for the U 47, while Neumann retained the privilege of choosing the best VF14 tubes for their microphones.
The VF14 Tube: The Powerhouse Within
One of the fundamental elements that shape the U47’s unique sound is the VF14 tube, a pentode vacuum tube. Enclosed in a robust steel housing, this tube serves as the beating heart of the microphone. It was specifically developed by Telefunken for the U47, and its intricate design and unparalleled specifications played a pivotal role in crafting the U47’s distinct sound.
The VF14 tube is a crucial component in amplifying the signal captured by the microphone’s capsule. It ensures minimal distortion, allowing for the replication of the most natural, ‘musical’ sound possible. When the VF14 tube ran out of production, its absence signaled the end of the U47’s original production run, a testament to its irreplaceable nature.
From 1946 to 1958, Telefunken manufactured 27,548 tubes in Berlin and Ulm, Germany. Approximately a third of these passed Neumann’s strict performance and noise assessments, earning a white “M” stamped on them, signifying “mikrofon”. Around 6700 of these specially marked tubes found their home in a U 47 or U 48. Neumann’s last order for VF14s occurred in 1958, and by 1963, when the supply had dried up, the U 47 discontinued production. This five-year interval, however, provided Neumann sufficient time to develop two new large diaphragm capsules and a novel flagship tube microphone, the U 67.
The M7 Capsule: Signal Creation
While the VF14 tube is impressive, its brilliance shines only as brightly as the signal it enhances. In the case of the U 47, the signal is produced by the fluctuations of the dual-diaphragm M7 capsule, which can switch between cardioid and omnidirectional mode. Initially designed for the CMV 3 bottle mic, the enduring M7 design is still being produced today by Microtech Gefell, who supplied many of the initial M7s from East Germany, before the establishment of the Berlin Wall.
This capsule is a genuine work of craftsmanship, with diaphragms made of PVC, just 12 microns thick, layered with a thin film of evaporated gold. These diaphragms are glued to dual backplates of brass, punched with precise patterns of 90 holes for accurate sound capture. The M7 design allows for cardioid or omnidirectional operation, enabling versatility in recording scenarios.
Although highly sensitive to sound waves, the PVC material would degrade over time. As the diaphragm aged, it lost tension and strength, resulting in hairline cracks and shrinkage, which permitted moisture penetration and caused conductivity losses. By 1960, a more durable replacement, Mylar® (a type of polyester), was identified and incorporated as the diaphragm in the newer K47/K49 capsule used in later U 47 mics and in the M 49.
The new design featured a single backplate and kept the diaphragm under tension with 12 screws in a brass mounting ring. Initially, capsules with the closest tolerances between diaphragms, signifying superior performance, were labeled K48/49, indicative of better performance in figure-eight mode for the U 48 and M 49. As production tolerances improved over time, the specific designation became superfluous, and all later capsules were officially marked as K47/49. Microphones equipped with the new capsule, usually identified as U 47a, appeared around number 4800, coinciding with a change in the transformer.
The Neumann U48 and Other Neumann U47 Variations
One intriguing version of the U47 materialized around 1955, known as the U47P. This variation featured a standard amplifier and body equipped with an old-style torpedo mount to hold an M48 omnidirectional capsule, very much like the aluminum capsule found in the small diaphragm tube condenser KM53, which made its debut in 1953. These microphones’ unique use of the U47 amplifier was coupled with an output impedance strapped for 600 ohms, a very uncommon feature for a U47. They were labeled with a “P” to signify a custom order for the Philips corporation. These units, manufactured in limited quantities during the mid to late 50s, could be reverted to the original U47 configuration by replacing the torpedo head with a KK47 assembly.
However, the most influential variant of the U47 is the U48, introduced in 1957. Approximately 800 U48s were produced before the model was phased out along with the U47. The fundamental difference between the U47 and U48 is that while the former is cardioid and omni, the latter is cardioid and figure-eight. This divergence is represented by the “8” in the model name, which indicates a polar pattern variation, not the production year. In cardioid mode, the microphones are almost indistinguishable, though the signal-to-noise ratio in the figure-eight setting of the U48 is higher due to a low polarization voltage.
Changes in the Design of U47 and U48
Originally, the U47 featured a long body, first made of brass and later aluminum, which was shortened by about an inch and a half when smaller components were introduced, and the transformer was mounted horizontally. By mid-1957, about 3,250 “long bodies” were produced, after which the rest were “short bodies”. The head grille, a crucial component contributing to the mic’s musical tone and enhancing the proximity effect, was available in two finishes: chrome for studios, and matte for TV and film.
Conversely, the U48 came into existence after the amplifier body was shortened, so all U48s are of the short body variant. The entire head grille and capsule assembly of a U47, known as KK47, can be fitted on a U48 body, but not the other way around. Therefore, all three polar patterns were achievable with a complete U48 and a spare KK47 head.
The Evolution of Logo Badges on the U47
Throughout the U47’s evolution, a constant source of change has been the logo badge affixed to the microphone. The first 300 or so U47s featured a “large badge”; a chrome diamond shape with the Neumann logo and the serial number on the body’s front. This was later substituted with the “small badge,” a metal diamond with a black lacquer finish featuring the Neumann (or Telefunken) logo. A separate serial number badge was either a rectangle placed at the body’s bottom rear or a semi-circle on the bell’s face. Some rare U47 models with a Siemens badge were custom-ordered from Neumann for broadcast use. As such, various bodies, badges, and grilles resulted in five different U47 aesthetics based on the badge type, plating, and body size.
The Superiority of the U47 Microphone
In the world of audio recording, if I had to select a single microphone for vocal recording, without a doubt, the U47 would be my top choice. The versatility and distinctive quality it brings to the table are truly unparalleled. It has also proven to be excellent on nearly any instrument.
The U47 is not merely a microphone. It is an enduring symbol of audio excellence, a testament to the genius of Georg Neumann and his team. Its timeless design, path-breaking technology, and the rich legacy it carries make the U47 an icon in the world of audio recording.
But the true mark of the U47’s greatness lies in its relevance. Despite the evolution of microphone technology over decades, the U47 continues to be a go-to choice for audio professionals worldwide. The list of iconic artists and engineers who have used this microphone is a testament to its enduring appeal.
In essence, the Neumann U47 is much more than just a tool for audio recording; it is a piece of history, a gold standard in sound reproduction, and in many ways, a benchmark for what microphones ought to be. As we step into the future of audio technology, one can only wonder if there will ever be a microphone that could match, let alone surpass, the legend of the U47.