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Mods for the U 47

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    Bill Bradley restores vintage mics in Nashville, TN.
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    Scott Hampton repairs vintage tube mics, especially those needing new power supplies. His mic repairs involve replacing and updating selected components, fine-tuning the circuitry, and restoration of the mic's original sonic character. He can also furnish a Hamptone second-generation Tube Mic Power Supply.

OmnidirectionalCardioidNeumann U 47

Multi-Pattern Tube Condenser Microphone

The original U 47, invented in 1947, was the first switchable pattern condenser microphone. It has become the most revered vocal microphone in history, and inspired dozens of attempts to recreate its sound.

The U 47 could produce either a Cardioid or Omnidirectional pickup pattern. The pattern switch was located on the microphone body, and worked by disabling the polarization voltage to the rear diaphragm.

U 47(The U 48, introduced around 1957, was a U 47 that provided either Cardioid or Figure-of-8 patterns. The only difference between Omni and Figure-of-8 patterns is the polarity of the rear capsule.)

The U-47 did not maintain equal output levels across patterns. This is a characteristic that Neumann engineers sought to improve in later mics, such as the M 49. The U-47’s output was 5dB hotter in Cardioid mode than in Omni, because the capsule’s rear diaphragm was simply disconnected in Cardioid mode, avoiding the capacitance losses of having it in the circuit. See the history of the M49 for more information.

The original U47 employed a Telefunken VF14 tube, which would become hard to find within a few years, leading to changes to the U47 design as well as the introduction of the U47fet, a FET condenser intended to sound the same as its tube-amplified sibling.

Early U47 (and U48) mics contained Neumann’s M7 capsule, in which the brass backplate was covered with a thin PVC diaphragm. PVC ages poorly, and as early as 1958 the Neumann factory was using the M7’s successor, a capsule known as the K47/49, which used a metallized polyester diaphragm.

The K47 capsule used a single, shared backplate, which caused tensioning challenges, in that both diaphragms would have to be tuned identically to produce balanced Figure-of-8 or Omni patterns.

In the original German-language Neumann documentation for the U47 and similar mics, the term “Niere” — literally “kidney” — is used to denote the Cardioid pattern. The term “Kugel,” which translates to “ball,” indicates Omnidirectional.

U 47 Group Photo
Photo: SouthernTracks.com

Bill Bradley

There were about 5000 [U-47s] made, about 3200 long bodies and the rest short. People say it’s gotta be a long body to be any good. False. They’re exactly the same microphone inside.

The mic went through three revisions. They started off with a very large transformer/capacitor package. If you pull the covers off you won’t believe; they’re packed. There’s no room for anything in there. If you take exactly the same mic that’s five or six years younger, take the shell off — you’ll wonder where the mic went.

According to Andreas Grosser, at least 5 different models of output transformer were used within the U 47. Four of them were called the BV-08, despite differences in mounting, appearance, and construction.

The approximate physical dimensions of the U-47 are as follows:

ModelLengthDiameter
Long body U-47240mm63mm
Short body U-47200mm60mm

The U47 was manufactured by Neumann, but initially distributed by Telefunken. Therefore, many early U47s bear the Telefunken logo. Neumann took over distribution in the 1950s; the mics distributed by Neumann bear a Neumann logo.

The Neumann U 47 is also known as: U47.

The mic was released in 1947.

Specifications

Frequency Response - OmnidirectionalClick Graph to Compare!
U 47 Omnidirectional Frequency Response Chart
Frequency Response - CardioidClick Graph to Compare!
U 47 Cardioid Frequency Response Chart
Pickup Patterns Pads & Filters
Omnidirectional (14 mV/Pa; 35 - 15,000 Hz)
Cardioid (25 mV/Pa; 35 - 15,000 Hz)
Capsule Dimensions Impedance SPL/Noise
Diameter n/a
200 Ohms (Low)
Weight Length Max Diameter Interface(s)
800g (28.22oz) 240mm (9.45'') 63mm (2.48'')
  • 3-pin XLR male (1)
Power Specifications
  • Includes tube power supply

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