ADK A-51TC, October 2001

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ADK made waves a few years ago with the debut of its A-51 (Area 51)
Series of affordable—around $400—large-diaphragm FET condenser mics. Following on that success, ADK
introduced a series of tube condensers, including the model A-51TC
reviewed here, and the flagship Area 51TT.

The A-51TC sports a—um—“classic” appearance
and is solid and well-built. Its aluminum casing measures 6.5 inches
long and 2.1 inches in diameter, and the mic weighs 18.5 ounces.
Inside, there's a 1-inch diameter capsule with a cardioidpolar pattern; the more expensive 51TT has dual
1-inch diaphragms and nine polar patterns, and a 6072 vacuum tube.
Sensitivity is given as 14 mV/Pa2 -37 dBV (0 dBV), with a frequency response of 20 to
20k Hz and a max SPL of 125 dB (1% THD @ 1 kHz). Retailing at $999, the mic
includes a power supply, shock-mount and hard case.

I used the A-51TC in my project studio during a two-month period. I
tested it using a variety of mic preamps, both tube and solid-state,
but mostly, I used the onboard mic pre's in my Yamaha 03D digital
mixer. The 03D's mic pre's are clean and were a good match for the
A-51TC's tube-driven character. By extrapolation, it is reasonable to
assume that the mic would perform well with most digital systems.

My first experience using the A-51TC was a poetry reading session.
The previous night, we had used another large-diaphragm tube
mic—which costs twice as much as the ADK—with mixed
results. The A-51TC had considerably more richness and character,
handled the sibilants and plosives much more smoothly and was easier
for the (male) talent to “work” closely without bumping up
against the proximity effect. It also sucked in the faint,
unwanted background sounds with greater definition and clarity, but
that wasn't the microphone's fault.

I also used the A-51TC to record acoustic guitar and dobro. In both
cases, I placed the mic slightly off-axis, about 18 inches away from
the playing area of the instrument, and got a full sound, with the
right touch of crispness in the top end. The lower frequencies on the
dobro were rendered particularly effectively, in balance with the
highs, which is not the case with many mics, even large-diaphragm condensers.

The A-51TC handles a variety of percussion instruments. It captured
both the low boom and the high “tok” sounds of a
long-throated doumbek while at the same time, picking up the most
subtle hand sounds—all in perfect balance. Placed just inside the
bottom of a small conga, the ADK delivered a tight, punchy sound. When
it was used to record a set of car keys on a ring (used as a percussion
instrument), there was no excessive scratchiness. In short, the mic
basically reproduced the full range of sounds present, without overly
emphasizing any particular frequency. That's not to say that there was
no personality imparted to the sound, because in all cases, there was a
tiny bit of (tube) fuzziness at around 8 kHz, but it was a pleasant

Placed directly in front of a blaring guitar amp, the A-51TC easily held its own, enriching the
sound with a throaty warmth, making the relatively small amp sound
huge, particularly on heavily distorted settings. Finally, the A-51TC
did an excellent job on a male blues vocalist, capturing the richness
and gritty complexity in great detail. The vocalist loved the
sound of the mic and asked if it could be used for a live

Overall, the ADK A-51TC has a large and likable sound, and the
coloration it does impart was a good match for a variety of sources,
especially those with complex harmonics and overtones. If you are
searching for a large-diaphragm tube condenser in the $1,000 range,
then you should give the A-51TC an attentive listen.

ADK Microphones,

ADK A-51TC Spec Sheet
Type: condenser pressure gradient
Vacuum Tube: 6072
Sensitivity: 14 mV/Pa2 -37 dBV (0 dBV=1-volt/Pa)
Bandwidth: 20 to 20k Hz
Impedance: <250 ohms
Max SPL: 125 dB (1% THD @ 1 kHz)
EIN (DIN 45405 CCIR 468-2): 28 dB
EIN (IEC 268-4, A-weighted): 18 dBA
S/N ratio @ 1 Pa: 76 dB
Connector: 7-pin XLR
Body Size: 6.5x2.1 inches
Body Weight: 18.5 ounces