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CardioidBock Audio 507

Cardioid Tube Condenser Microphone

The Bock 507 is large-diaphragm, fixed-cardioid tube mic employing a unique, patented elliptical capsule.

Bock 5ZERO7 CapsuleThe capsule design, conceived by George Cardas, was developed and refined in a collaboration between Cardas and David Bock. The elliptical shape, also known as a “golden ellipsoid,” reduces diaphragm resonance within the audible band, and as a result the capsule delivers both a clear and detailed high-end and a full low-end. In the 507, the capsule measures approximately 1'' by 1.5''. The ratio of length to width is approximately 1.6 to 1.

George Cardas tells us:

George Cardas

I have been building and designing microphones since the early 90’s as a hobby and in conjunction with my recording efforts. It became apparent at some point that the tympanic qualities of the diaphragm were related to the shape and tensioning of the diaphragm. This lead to a series of prototypes that dealt with [non-traditional] dimensions. As with other music-related phenomena, I found that the most musical shape had the major and minor axis relationship of 1.618 to 1, or “Golden Ratio.”

The capsule in the 507 has two diaphragms, but the rear diaphragm is not connected electronically (although its presence alters the response and sound of the front membrane). Both are gold-sputtered Mylar; the backplate is brass. The capsule uses an edge-terminated, rather than a center-terminated diaphragm. David Bock tested both and determined that the edge-terminated design provided a flatter, “less peaky” response than the center-terminated design.

Bock Audio 507 microphoneAs with most of the capsules used in the Bock Audio lineup, the 507’s capsule is custom-manufactured in Germany by MBHO.

The amplifier circuitry within the 507 is based on the tube U47 design, using a NOS Telefunken EF814, aka EF814K (with the ‘k’ suffix added by Bock) tube — not widely known, but previously used by Bock in the Soundelux E47C. About the tube, Bock says, “We like it because it has a lot of similarity to the VF14, without being a metal jacket.”

Although David Bock has previously designed mics inspired by the U47 — e.g., the E47 and E47C — he says the preamp circuitry in the 507 is even more true to the U47 design.

The mic has no pad, no filter, no tone switches of any kind.

Internal wiring is Cardas, according to Transaudio president Brad Lunde*. The cable that runs between the mic and the power supply is Gotham GAC7, a flexible 7-conductor cable with two layers of shielding and an outer PVC jacket.

The 507 was officially introduced at AES San Francisco in October, 2008, and began shipping shortly thereafter. The model name is “507,” pronounced “five zero seven” according to Brad Lunde of Transaudio Group (Bock Audio’s distributor).

Bock Audio 507It will include an elastic shockmount.

Bock will likely offer a multipattern version of the 507 in the future, probably based on the Soundelux EL308 (a multipattern Golden Ellipsoid mic that was prototyped but never released).

David BockThe 507 differs from the 251 capsule in that the proximity effect is not so great as in Bock’s 251 capsule. But our 251 probably has more than the average 251 because we have that big transformer.

The transformer was designed specifically for this microphone, and is manufactured by AMI/Tab-Funkenwerk.

The Bock Audio 507 is also known as: 5-ZERO-7.

The mic was released in 2008.


Pickup Patterns Pads & Filters
Cardioid (20 - 20,000 Hz)
Capsule Dimensions Impedance SPL/Noise
Diameter n/a
Weight Length Max Diameter Interface(s)
n/a n/a n/a
  • 3-pin XLR male (1)
Power Specifications
  • Includes tube power supply

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