Search Microphones

Share This Page

Related Microphones

OmnidirectionalBock Audio 50

Omnidirectional Tube Condenser Microphone

The Bock Audio 50 is a pressure omni tube condenser, designed to recreate the sound and character of a vintage Neumann M 50.

This mic retains the critical elements of the M 50: The capsule is a half-inch omni condenser capsule, inset into an acrylic sphere. The amplifier circuit is based on the M49/M50 circuit. The output is transformer-coupled, and the transformer, according to expert Oliver Archut, uses identical alloys and winding methods as used in the original M49/M50 mics. (Presumably, Tab-Funkenwerk created the transformer used in the Bock 50.)

There are several differences from the old Neumann mic: the Bock 50’s sphere is slightly larger than the M50’s 4cm design. The Bock 50 capsule uses a Mylar diaphragm, which was true only of later M50 editions — the first few generations used PVC, then aluminum-membrane capsules. The Bock mic’s circuit does not use an AC701 tube. The values of numerous resistors and capacitors were changed.

Whatever alternative parts were used were selected after extensive listening tests. As David Bock commented about his extensive prototyping process, “component selection mattered.”

The Model 50 uses an EF732 (aka 5840) subminiature pentode tube in the amplifier circuit. This model tube has been described by David Royer as being “electrically similar” to the Neumann M50’s AC701.

The use of an omnidirectional capsule mounted within a sphere was pioneered by NWDR, Northwest German Radio, around 1948. The sphere has the effect of raising and smoothing the capsule’s high-frequency response, essentially acting like a high-shelf EQ. The capsule in this system becomes more directionally sensitive at mid-to-high frequencies, resulting in a microphone especially suited to ambient miking applications such as orchestral recording.

The body of the Bock Audio 50 is a hybrid of the M 50 and TLM 50 designs, with the lower half being true to the M 50, including the white “jewel” on the body above the logo badge. The grille design departs from the M 50’s 3-layer mesh and sloped face, instead using a domed-cylinder design similar to the TLM 50. That said, the Bock 50’s grille is made of a single-layer mesh, which produces less acoustic coloration than would a denser material, and which therefore contributes to the mic’s “open” and clear sound.

The Model 50 was benchmarked during development against the Neumann M 150 Tube, which is the closest mic to the M 50 currently in production. David Bock believes the new mic offers superior performance to the Neumann M 150.

We will update this profile when specs for the new microphone are made available.

The Bock Audio 50 is also known as: AM 50.

The mic was released in 2009.


Pickup Patterns Pads & Filters
Omnidirectional (n/a mV/Pa; n/a)
Capsule Dimensions Impedance SPL/Noise
Diaphragm diameter: 12mm
Weight Length Max Diameter Interface(s)
n/a n/a n/a
  • 3-pin XLR male (1)
Power Specifications
  • Includes tube power supply

Did we get anything wrong on this page? Please let us know!