The KINAP 10a1 is a dual element microphone that uses a bi-directional ribbon and an omni-directional dynamic capsule. It is essentially a Soviet version of the Altec 639b and the STC 4033 which all implement a three-way switch that selects between the ribbon (figure-of-8), the dynamic (omni) and a combination of both (cardioid). There is an output transformer inside the body of the mic and a second output transformer built into the connector (the big donut at the base of the mic), likely for impedance matching.
The mic in the photo was manufactured in 1950 at the KINAP factory, and is in great condition considering its rarity and its age. The 10a1 is one of those “mythological” mics that I never expected to see in person. When we finally acquired one I was truly excited to move some air into it. But listening back to the recording I was disappointed to discover that it was lacking low end and sounded harsh in the upper midrange even after installing a new ribbon. For a while I figured this mic was destined to be nothing more than a cool piece of history.
But in the back of my mind, I knew something wasn’t right. I discovered an original technical brochure (swipe to see) which describes an LCR band-pass filter installed between the two transducers and the output transformer. This isn’t the first Soviet ribbon mic I’ve seen with an LCR network in it (every Oktava ML11m I’ve seen has had one). The purpose of this, as far as I can surmise, is to optimize the mic for use with public announce systems to prevent low and high frequency feedback, and/or to highlight the vocal range range for speeches for broadcasts and public announcements or performances. I’ve included a photo of Ravi Shankar playing into a 10a1 for a private performance at The Kremlin.
The mic was sent to John Peluso to bypass the LCR network (while leaving it intact so it could be reverted to original). He also cleaned up the dynamic capsule which was pretty gunked up. The microphone came back sounding the way I had always imagined it - a full round sound with a balanced midrange, a gorgeous bottom end, and a soft top end.
