After more than five years of development and testing with critical recording engineers in Europe and the USA, Josephson Engineering is now shipping the C725 hybrid vacuum-tube microphone — their first production model to use a vacuum tube. Designed and manufactured in their facility in Santa Cruz, California, the C725 is a new twist on an old challenge: how to get a compelling studio sound pickup in a reliable and flexible package, that can be maintained with currently available components.
Engineers want the ‘smooth’ and ‘warm’ tube sound without loss of detail, and with precise capture of subtle musical nuances. However, designers have been faced with obstacles of tube selection, noise and reliability using traditional circuits. Now the company have developed a circuit using the cascode topology already used in most of their other mics, but with an FET and a tube doing the work rather than two FETs as with other models. The capsule, which is the same dual-diaphragm multi-chamber design used in the C700 and C716, is manufactured in-house.
One of the major contributors to harshness and high-frequency artifacts that detract from the smoothness of a microphone is the set of reflections inside the microphone grille, say Josephson, which for many large-diaphragm mics results in resonances in the sibilance range. To combat this, Josephson Engineering have developed and patented an aluminium foam grille that’s fused to the microphone housing and then machined as one continuous piece of metal. Because the structure is random, there’s no concentration of reflections in a narrow frequency band. They claim that the grille’s influence on microphone sound is greatly diminished — sibilance is not boosted, off-axis pickup is not compromised, and an absence of concentrated high Q resonances means the microphone can “take EQ well,” say its makers.
The circuit inside the microphone uses a FET and a vacuum tube in cascode configuration, and a custom nickel-core output transformer. This allows the low noise of the FET to be combined with the dynamic characteristics of the tube. This, say Josephson, is like having two different microphones in one. A ‘sun’ mode provides full gain with noticeable tube character, while the ‘moon’ mode is designed to be a little cooler, with less gain, a higher overload point and a more neutral sound. The mic is furnished with a dedicated power supply that operates from 100-130 or 220-250 VAC. Two stages of heater regulation are provided so the tube has a constant operating point even with extended mic cables. Meanwhile, polar pattern and sun/moon mode switches live on the power supply front panel.
Concurrent with the release of the C725 microphone, Josephson Engineering have announced that Liverpool headquartered Studiocare Professional Audio has been appointed as an authorized dealer in the UK. David Josephson reports, “…when I first met Richard Threlfall and Rick Whalley, I was impressed by their understanding of microphone technology and the high level of customer service they offer at Studiocare.” Studiocare has acquired the first C725 in the UK and it's now part of their extensive demonstration and hire inventory for demanding engineers to evaluate and add to their arsenal of tools. The C725 is available now, priced at $8,800.