Bock Audio 251 Microphone

WHAT IS IT?:
The vintage 251 is THE vocal sound people ask for, but the original (vintage) versions are 50+ years old and sound very different from one another. Repairing, rebuilding and “nursing” original 251’s along has been David Bock’s work spanning over 30 years. The risk for a modern studio or end user to depend on a vintage mic on a daily basis is increasingly problematic.
The BOCK 251 is David Bock’s answer to the vintage mic dilemma of getting “that sound” without the headaches. It is a premier lead microphone for premier voices. It is built to last and provide the studio and user with many years of daily, high end performance.

WHAT MAKES IT DIFFERENT?
The BOCK 251 provides the user with absolute confidence that this is the mic you put in the most critical situations. The BOCK 251 uses a proprietary hand made German capsule, a proprietary hand wound multi sectioned audio transformer, a NOS tube in the mic amplifier, a hand built outboard power supply and a custom low capacitance audio cable. This is one of the best overall mic packages available on the market at any price. The BOCK 251 is the ideal microphone to choose when there is a variety of applications that must met with absolute top recording quality. With frequency response that extends well beyond the normal range of typical studio microphones, the BOCK 251 sets new standards.
For vocals, the BOCK 251 instantly delivers that huge vocal sound you have wanted for years. It sounds equally impressive on females and males. It will capture the most intimate and subtle details of a vocal yet maintain integrity at high SPL’s. It holds up track after track, “sitting on top” in extremely dense mixes without EQ.
For instruments, the BOCK 251 offers very high end performance on critical stringed instruments, orchestras, choirs and small ensembles. The outstanding transient response reveals elusive harmonic details that spell the difference between good and great in your recordings.

HOW DO I USE IT?
The BOCK 251 cardioid pattern shuts off the back of the capsule to deliver extraordinary vocals when worked very close. It is recommended to use a pop filter on less experienced vocalists to enable closer working distances to take advantage of the magical proximity effect. There is no low frequency filtering used on a BOCK 251 so you will hear low frequency content you’ve never heard before.

At distance, the BOCK 251 delivers a level of definition that is amazing. The high end does not fade with distance like so many other condensers and the power and depth of the low end response is a joy to hear. The omni and Figure 8 patterns prove useful in these non-voice applications.


Technical advantages the 251:

1) True transformer balanced output using hybrid lamination four section transformer*. Our transformer is ten times the size of the original so you get no rolloff in the low end until 8Hz (with no loss of high frequencies), making our mic more full bandwidth than the original.
2) NOS dual triode** with traditional resistive (not transistor) load and enhanced original circuitry for unique vintage amplification curve and dynamics response!
3) Selected ck12 type capsule.
4) True linear power supply featuring choke fed, passive shunt regulated B+ voltage and new super-quiet heater regulation, providing a better hum and noise spec than the original.
5) Original headgrille dimensions and wire mesh layers are maintained for faithful replication of classic 251 headgrille resonance effects.
6) Higher wattage resistors reduce noise effects due to heating inside the mic.
7) Shock mounted ceramic tube socket unlike any other in the industry reduces in-band tube resonance & increases s/n while ensuring long trouble free life.
8) Switchable three patterns on mic: omni, cardioid, fig 8. Cardioid completely removes the rear membrane and it’s associated circuitry from the signal path ensuring an optimized tone and s/n.
9) P251 power supply has power on indicators located at both ends for quick and easy “power on/off” status verification.


Specifications:

Patterns: Cardioid, omni, Figure of 8 Switchable from mic
Frequency Range: 10Hz to 18kHz, +/-2dB
Sensitivity: 19mv/Pa
Equivalent Noise: 18dB (“A” weighted) 32dB (unweighted)
Distortion vs.SPL @1kHz:
112dB = 0.5% THD
118dB = 1% THD
129dB = 2% THD
(increasing distortion is non-exponential, nearly linear, and primarily 2nd harmonic)
Impedance: 200 Ohms true transformer balanced
Recommended load: 1.2k Ohms
Dynamic range (maxSPL-"A"noise): 94dB
S/N (94dB-noise): 76dB “A”, 62dB unweighted
Capsule size: 1” diameter, dual asymmetrical backplate CK12 type
Tube type: New Old Stock GE5670 triode
Dimensions: 2” dia x 8.5” oal (52x216mm)
Weight: 1lb 9.3oz (1.58lbs) =716g
Shipping weight: 12 lbs
Power Supply: P251 true linear, factory wired 115v or 230v operation