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Tuesday, September 28, 2010

The Sony C-37A At 55 Years On

There are certain pieces of audio gear where the manufacturer gets it right and creates a classic, but doesn't realize it until years later after the unit has been replaced with a new "updated" version that doesn't sound as good.  The Sony C37A microphone is one of those pieces. The illustrious George Peterson wrote a wonderful article for Mix Magazine about the history of the C37Aa a month or so ago that I think is well worth repeating below.

The large Sony logo on the mic helped spread the word about the C-37A.
The large Sony logo on the mic helped spread the word about the C-37A.
In the early 1950s, Japan didn’t manufacture condenser microphones. Imported European models such as Neumann U47s were highly coveted, although very expensive. Seeking a domestic alternative, Heitaro Nakajima—of the Science and Technical Research division of Japanese broadcaster NHK—was interested in building a condenser mic, having seen a U47 during recent travel to Germany. NHK’s first attempt at creating a condenser mic was based on a silver-coated celluloid diaphragm, which was noisy and would burn if the DC bias voltage was too high. NHK eventually scrapped the project. [Note: After 24 years at NHK, Dr. Nakajima left in 1971 to oversee R&D activities at Sony and was instrumental in moving the company forward into PCM-based recorders and later the co-development of the Compact Disc with Phillips.]
Upon hearing from Nakajima about the NHK prototype, Sony engineer Kanane Nakatsuru wanted to build a condenser microphone. He experimented with numerous diaphragm materials, finally settling on DuPont’s Mylar, which had just become available in Japan. Mylar had the strength and tensile properties Nakatsuru was seeking, but he was unsure about how to add a conductive gold coating to the material. Sony co-founder Masaru Ibuka suggested that Nakatsuru contact someone he knew who had developed a sputtering method of layering gold vapor onto various materials. It worked with Mylar films, as well, and Sony’s first condenser mic project moved ahead. The mic capsule, which eventually was called the C-3, was a single-diaphragm design using a 6-micron Mylar diaphragm.
The electronics side was less complicated, but the cost of the Telefunken AC-701 miniature triode vacuum tubes used by European microphone manufacturers were prohibitively expensive in Japan. Nakatsuru instead went with a single-stage amplifier using a cathode-follower design as an impedance converter with a readily available (and far more affordable) 6AU6 pentode tube configured as a triode.
Sony C-37A and CP-3B power supply
Sony C-37A and CP-3B power supply
The C-37A took its name from the outer diameter of the C-3 capsule element, which was 37 mm. On seeing the completed prototype, Ibuka proposed the idea of putting the Sony name in large letters across the mic’s center band. So when the mic appeared on Japanese television broadcasts, the Sony brand would be visible, especially in close-ups on singers or newscasters. The concept worked and the word soon spread about Japan’s first condenser microphone.
The mic was released in Japan in 1955, although it didn’t make its official debut in the United States until the Los Angeles Hi-Fi show in 1958.
The C-37A design features a slot on the back on the mic grille for mechanically changing the polar pickup pattern. Turning the slot to the right selects the “N” non-directional (omni) pattern, while turning it to the left selects the “U” uni-directional, which is essentially cardioid at 1 kHz, becoming tighter at higher frequencies.
On the CP-3B power supply is a rotary, 4-position highpass filter switch offering four choices in low-frequency roll-off. The M (Music) position was essentially flat, with M1 (Music 1), V1 (Voice 1) and V2 (Voice 2) offering progressively increased bass attenuation. A pushbutton is also provided to enable a high-frequency roll-off curve. The underside of the CP-3B has recessed switches for selecting impedance (50 or 250 ohms) and output level settings. Inside the power supply are multiple taps for operating at 100, 117 or 220 VAC.
Specs included a 30 to 16k Hz frequency response. The entire package shipped with mic, power supply, an attached 10-meter mic cable, carrying case and manual. It also included a 21-3P audio output connector so the user could make a custom output cable that interfaced to whatever connection that was required. (This was in the pre-XLR days, when universally standard audio connectors didn’t exist.)
Sony’s C-800G (left) and C-800 mics have similar names, but the mics are quite different in design and sound. Unfortunately discontinued today, the C-800 comes close to being a modern reissue of the original C-37A.
Sony’s C-800G (left) and C-800 mics have similar names, but the mics are quite different in design and sound. Unfortunately discontinued today, the C-800 comes close to being a modern reissue of the original C-37A.
The C-37A was followed by the solid-state C-47FET (with onboard 9-volt battery powering) and the phantom-powered C-37P version. However, perhaps the most interesting Sony model to follow the C-37A decades later was the C-800 released in 1992, which, aside from its outer body style, was a near-perfect clone of the C-37A with a few modern improvements, such as higher output and lower self-noise. Unfortunately, the C-800 was launched at the same time as the much-heralded C-800G—a far more expensive, dual-diaphragm tube mic that featured an innovative outrigger Peltier cooling device. Lost in all the hoopla, the C-800 never got the attention it deserved, and sadly was eventually discontinued, although the C-800G remains in production and is a highly regarded choice, particularly on pop vocals.
Like the C-37A, the C-800 had a single-diaphragm capsule, used a mechanical vent to change polar response and was based on the same 6AU6 pentode tube. In fact, the elements of the C-37A and C-800 are so similar that a C-800 capsule can be employed as a replacement part for a C-37A. Tip for Sony: Bring back the C-800, perhaps as the C-800A, but with a cool retro finish so it doesn’t resemble the C-800G, and this time around actively promote its C-37A heritage.
Today, some 55 years after its initial launch, the Sony C-37A remains a viable tool that is still prized in studios throughout the world. Typical C-37A applications include horns, acoustic bass, strings, guitar, banjo, mandolin, drum overheads and vocals. And among the mic’s most ardent fans is Daniel Lanois, who has used his C-37As on a long list of top artists he’s produced, such as Bob Dylan, Bono and Peter Gabriel.
Not bad for a microphone that was designed more than a half-century ago.

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1 comment:

Eric Weber said...

The self noise is the same, please read the specification sheets for the C800 and C37A,,, they were done at a different reference SPL. The C800 has the audio transformer on the microphone end of the cable so is much more immune to noise from adjacent cables... common mode issues... I have a pair of each :-)


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