Microphone Masterclass: Sony C-37A

Microphone Masterclass: Sony C-37A full HD 16x9 thumbnail

Japan Takes On The World With An Underappreciated Classic

One of the hidden gems of the Bill Putnam Mic Collection, available for users of the Sphere L22 and the Universal Audio UAD-2 and Apollo DSP platforms, is the BP-37A. Recently, Sphere version 1.5 added the LD-37A and LD-37P models to the Sphere L22’s growing mic model collection. These models, which excel at taming brittle or sibilant high end without harming the essential quality of the source, are based on a remarkable microphone that’s overlooked far too often when considering the truly great mics of yesteryear. Let’s take a trip to Japan, just after World War II, and uncover the story of the Sony C-37A and its descendants in this Microphone Masterclass.

As Japan entered the 1950s, it essentially had no microphone industry. While recovery under the Marshall Plan was slowly restoring prosperity to the war-ravaged country, fledgling Japanese companies got their start manufacturing inexpensive and often lower-quality imitations of American and European products. These days, people sometimes say “Made in China” disparagingly, but in the mid-20th Century, the pejorative was “Made in Japan.”

One company that had aspirations beyond being just another imitator was Tokyo Tsushin Kogyo, or Tokyo Telecommunications Engineering Corp. Founded in 1946 by Masaru Ibuka and Akio Morita and initially run out of a small electronics shop, TTK made history with the Type-G, Japan’s first locally-manufactured tape recorder. Later, the firm branched out into the making of high-quality transistor radios that were easily the equal of American and European models. Those products carried the familiar brand name of Sony, which became the corporation’s official name in 1958.

Years before that, the Sony logo was already appearing on products taking the world by storm – and in one corner of the audio world, quietly making history. Find out more in the next chapter of our Microphone Masterclass about the Sony C-37A.

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The fire of inspiration (literally)

In the early 1950s, without the Internet and with printed technical journals taking weeks or months to see press, one of the fastest ways to learn about new technology was to attend research conferences. Heitaro Nakajima, an engineer working for Japan’s national broadcaster NHK, attended one such event in Germany. There, he got to see and test the U47 and other microphones made by Neumann, which at the time were considered unparalleled. 

Intrigued by the possibilities (and daunted by the prospect of buying a large number of expensive Neumann mics for NHK’s needs), he returned to Japan and began building a prototype condenser mic based on Neumann’s design principles but with some innovations of his own. Following some highly successful orchestral recording sessions, Mr. Nakajima told Sony about the prototype – which by then was about to be, or had already been, abandoned by NHK.

Why would the project be left on the junk heap if it sounded so good? Because in the early 1950s, Japan was still playing catch-up to the rest of the world in several vital areas of engineering, including the availability of certain industrial plastics. The only prospective diaphragm material Mr. Nakajima had readily available was celluloid film, coated with silver to carry electrical current… and that, to put it mildly, was a problem.

Celluloid was a major plot point in movies like Cinema Paradiso and Inglourious Basterds for one simple reason: it was flammable… and we’re not talking “set a match to it and it will burn” flammable, we’re talking “leave it in a hot car and it will explode” flammable. Celluloid ignites at the slightest provocation, and burns via a chemical reaction that requires no outside air to keep burning — it’s almost impossible to stop until it burns out on its own, producing noxious fumes as it does.

Tube mics don’t necessarily generate a whole lot of heat, but if the DC bias in the prototype was turned up too high, the waste heat was enough to start the chemical reaction in the celluloid, and you can imagine the rest. There was never any danger to life and limb: the amount of celluloid in the diaphragm, which was only a few microns thick, was tiny. However, a mic that would sometimes go “foof!” and emit a wisp of nasty-smelling smoke was deemed impractical.

Microphone Masterclass Sony C-37A photo Townsend Labs 2048px

Thanks to its classic u-shaped shockmount yoke and other design details, the look of the Sony C-37A strongly resembles classic American ribbon mics or the era, such as the RCA 77-DX.

Inspiration becomes innovation

Having learned about the prototype and been inspired by the exceptionally clear recordings made with it, Sony engineer Kanane Nakatsuru attacked the exploding-diaphragm problem with enthusiasm. He eventually designed a diaphragm made of gold-sputtered Mylar, which was well-known in other countries but had only recently become available in Japan. The new diaphragm was stable, reliable, far less noisy than the celluloid had been, and became the basis for the C-3 capsule, Sony’s answer to the famed K47 and other Neumann designs.

The C-3 used a single diaphragm, 6 microns thick and 37 mm (about 1.5”) in diameter. At the time, nearly all condenser multi-pattern mics required two diaphragms, and would obtain different polar patterns by varying their relative voltage. To keep the design clean and simple, Sony took a mechanical approach to the problem rather than an electrical one.

Years earlier, RCA had created directional and even variable-pattern ribbon mics (for example, the KU3A and 77DX) by using an adjustable tuned acoustic chamber to alter the response on one side of the normally-bidirectional ribbon. Similarly, Sony placed such a chamber on the back of the C-3, with ports that could be opened and closed from the outside. Once you got over the unnerving experience of sticking a screwdriver into a mic grille, you could continuously adjust the polar pattern from cardioid to omnidirectional – keeping in mind that even the most ‘omni’ setting retained significant directionality at higher frequencies.

Electronic design details

Like some other mics of the era, the electronics were based around a single-stage tube amplifier. This amp didn’t sound quite like European designs, since it used a 6AU6 pentode tube (run as a triode) rather than the much rarer and more costly Telefunken tubes used in Europe.

Sony placed the mic’s filtering controls on the power supply. There was a button to activate a treble roll-off (5 dB down at 10 kHz), and a 4-position switch enabling different amounts of bass roll-off. These were labeled M, M1, V1, and V2 (for Music and Voice).

Put all of this together, and Sony had created the C-37A mic (read back to figure out where the “37” came from). For reasons of simplicity, practicality, and easy access to parts, it was a pretty significant departure from the well-loved European mics of the day. The question remained: would this new design suffer in sonic quality when put up against the best of the best?

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Trial by fire (not literally)

The C-37A was tested in Japan in prototype form through 1954, and put into production in 1955. It was made available for sale in the USA in 1958, and very quickly became the go-to mic for a wide variety of music applications – so much so that Capitol Records bought them by the bushel and made them available in every studio.

It gave rise to many descendants, most famously the C-37 FET (Japan’s first solid-state mic) and the phantom-powered C-37P. Famous in its own right, the C-37P had the same 4-position bass roll-off as its tube ancestor, accessible on the mic body, and retained the adjustable polar pattern on the capsule.

Sphere 1.5 Meet your new mics panel for microphone masterclass 1200px

The Sphere software update 1.5 introduced the LD-37A and LD-37P models based on Sony's original tube and solid-state mics to the Sphere system.

Today, Sony still manufactures the C-38B, a modern design that retains the 4-position bass roll-off, adds an 8 dB pad and internal high shelf EQ switch, and uses a simple omni/cardioid switch rather than the tuned chamber on the capsule. It’s an excellent mic, but there’s something about the C-37A that’s uniquely sweet.

While the mechanical polar pattern adjustment on the C-37A and its progeny never became common, it is still used today by some of the world’s most respected mic designers. Shure uses it in the KSM141 small-diaphragm condenser mic, and Josephson revived it in the C715 large-diaphragm condenser.

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Comparison of the three "37" models available for the Sphere L22 microphone modeling system: The LD-37A, LD-37P, and the BP-37A from the UAD Bill Putnam Collection.

The Sounds of the Sony C-37A

This Microphone Masterclass about the Sony C-37A wouldn't be complete without any sound examples. Hear how different our LD-37A based on a vintage Sony C-37A sounds compared to our LD-87 Modern model in the comparisons below. Both microphone models are part of the included Core Collection of our Sphere L22 microphone.

A secret weapon in a world of Euroclones

Since its heyday, the C-37A has been the subject of surprisingly little discussion, much of it in the form of arguments about whether any of the stories about the mic’s accomplishments are true. Did Capitol Records really rely on it to get perfect first takes from the notoriously-temperamental Frank Sinatra? (Probably not.) Did famed conductor Bruno Walter really say of it, “This microphone conveyed my music”? (Probably so.)

Many lovers of “conventional” large-diaphragm condenser mics (and their pronounced presence peaks) dismiss the Sony, with its 30 Hz–16 kHz frequency response, as being too dark. Others note that its restrained high end produces beautiful clarity on everything from human voice to a variety of acoustic instruments as well as drum overheads, toms, and even electric guitar amps. It is an intimate mic, working very well in close-miking of strings, and the variable bass roll-off easily allows the engineer to strike the perfect balance between removal of unneeded bass noise and preservation of the source’s low-end character.

Recording engineer Bill Putnam Sr. – the founder of Universal Audio – loved the C-37A mics in his locker, one of which was modeled to create the BP-37A. A C-37A from another studio was used as the basis for the LD-37A model included in Sphere 1.5, which also features the LD-37P, a model of the C-37P. This solid-state mic model preserves much of the character of its tube predecessor, while offering a slightly brighter sound that’s excellent for adding just a bit of sparkle to darker source material.

The C-37A has become that most precious of microphones: a secret weapon for exceptional recordings that defies the conventions of the ubiquitous Neumann-based designs out there. These three models bring that sound – magnified tenfold by all of the possibilities inherent in a modeled mic – to users of the Sphere L22 system. It is our sincere hope that this Microphone Masterclass about the Sony C-37A helps you appreciate these unique models even more.

Dr. Mike would like to thank his friend and colleague George Petersen for useful background and fact-checking.

Are you interested in more articles like this microphone masterclass about the Sony C-37A? Check out this deep dive about the iconic AKC C12 microphone:
Microphone Masterclass: AKG C12 full HD 16x9 thumbnail

With Sphere you now can:

  • Record with the sound of microphones many have only dreamt about
  • Change mic type, polar pattern, and other microphone characteristics, even after tracking!
  • Audition the sound of different microphones without tiring the vocalist
  • Reduce bleed, undesirable room coloration, and other common issues using Off-Axis Correction™
  • Record in stereo from a single microphone

You are invited to install the free, fully-featured Sphere plug-in for all major platforms and DAWs. Try it now and reimagine our library of pre-recorded tracks.

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