Bock Audio: IFET Condenser Mic

While there are more new microphone models being manufactured now than ever before, most of them will never attain the classic status (nor hold the resale value) of an older Neumann U 47, AKG C 12, Telefunken Ela M 251, or RCA Type 44. But, there are a number of companies, including Bock Audio, who are building contemporary mics that easily rival the classics that inspired them — in build quality and in sonic performance. With that said, if you were to put together a list of mics that you and your engineering buddies would consider essential and timeless, I'd bet that very few mics still in production would be on that list. The Royer R-121 ribbon [Tape Op #19], for example, would be one of the few new "classics." But, I'd argue that the under-appreciated Bock Audio IFET should also be on that list.

At first glance, the IFET looks a lot like the familiar and classic U 47 fet, a mic that Neumann manufactured from 1969 to 1986, and reintroduced in 2014 as a "Collectors Edition." The IFET has rock-solid build quality, and all of its parts look and feel expensive; there is no mistaking the IFET for a cheap "Fet 47" knockoff. While the IFET does clearly draw upon the sound and heritage of the U 47 fet, designer David Bock [Tape Op #78] did make some improvements along the way, and he even added a clever twist, as the IFET is inspired by not one, but two classic mics! But first, let me tell you a little bit about Mr. Bock.

While David Bock was working as the chief tech in several classic and seminal studios, including Hyde Street in San Francisco, Hit Factory in New York, and Ocean Way [Tape Op #106] in Los Angeles, he developed a discerning ear for the subtle but crucial differences between good and truly exceptional microphones, as well as a deep understanding of what made these mics sound the way they did. With these decades of experience repairing mics under his belt, Bock co-founded Soundelux Microphones in 1995 with one of the owners of Soundelux (the now defunct post- production company) in order to manufacture new mic designs as well as recreations of classics. He parted ways with Soundelux in 2006, taking all of his work with him, and formed Bock Audio, with the stated goal to "design for sound, not a price point."

In that way, the Bock Audio IFET is an updated and improved "reissue," so to speak, of the Soundelux ifet7, which was first released in 2002. It uses a center-terminated, single-backplate, dual-diaphragm K 47 capsule, just like the U 47 fet. Bock carefully examined the multiple variants of the U 47 fet, and he concluded that one version of the U 47 fet's electronics sounded the best to him (and to many other U 47 fet owners too) — the only difference being the amount of negative feedback in the circuit, which was determined by a single capacitor value. It was perhaps a change in one small component, but it made an audible difference. Bock based his electronics on that version, but he improved upon the design by utilizing a higher-spec, larger-core transformer, and by simplifying the circuit (something he could do because of the consistency of modern electronic components).

But here's the clever twist. Bock didn't stop at just making a higher performance "Fet 47." As he explained to me, "Not everyone has a fortune to spend on a lot of microphones. I was curious what would happen if I took the K 47 capsule and married it to the U 87 amplifier." The Neumann U 87, as we know, is Neumann's other "classic" phantom-powered LDC mic. Unlike the amplification in the U 47 fet, which utilizes an input FET and four other transistors operating together as a discrete op-amp, the circuit in the U 87 relies on a single FET driving the output transformer directly. Bock started to wonder if it was possible to combine both amplification circuits into one mic. Well, that's what happened (more or less). The IFET (like its ifet7 predecessor) has a switch on it labeled I and V. In I mode, you are listening to the discrete op-amp amplifier. In V mode, the single FET. Keep in mind that an actual U 87 uses a K 67 or K 87 dual-backplate capsule, not the K 47 capsule in the IFET. Bock also modified the U 87 circuit, removing frequency- shaping elements that were necessary for the K 67 capsule (and unnecessary for the K 47), and decreasing negative feedback (ultimately making the IFET's V circuit more like the KM 84's).

What about improvements to the IFET over the ifet7? The original Soundelux ifet7 suffers from two common problems: eventual failure of the I/V switch, and stripping of the attached mount's threading after years of use. Bock Audio has addressed both of these issues, and owners of the Soundelux model can contact Bock Audio to schedule service for switch and mount replacement. Additionally, minor tweaks were made to the electronics to improve reliability, and the material for the base of the mic was changed from brass to aluminum, changing the balance point of the mic so it holds its position better.

We've had a Soundelux ifet7 at Panoramic House (and previously The Hangar) for over a decade, and all of the engineers at my studio use it on pretty much every session. Is it on the kick drum 90% of the time? Is it on the bass cabinet the rest of the time? Yes, to both questions, but we've also used the mic on lead vocals, acoustic guitars, percussion, and just about anything you'd consider recording with a high-end LDC — all with great results. It's also a smart choice for remote sessions, as the switchable amplification is like having two great mics in your mic case, while only taking up the space of one.

We're fortunate to have a well-stocked mic locker at Panoramic House, so when mics need fixing as mics occasionally do, I rarely get complaints from engineers when I pull a mic to get it serviced — they just use something else. This is not the case with the ifet7. When I sent it to Bock Audio to have them replace the older Soundelux I/V switch, I was constantly being asked, "Dude is the ifet7 back yet?" So, the next time it needed servicing to replace the Soundelux mount, I asked Bock Audio for a loan on an IFET, partially to keep the troops happy, but also so we could evaluate the newer mic. We used the Bock Audio IFET for several months, even after our repaired Soundelux ifet7 was returned; and we all agreed, the newer mic sounds fantastic, just like the older model. But in the end, we loved the patina that had built up on the body of our ifet7, a testament to its decade of constant use, so we returned the IFET. I'm happy to say, our ifet7 is back home at Panoramic House, where it will remain one of our cherished classic mics for as long as I own my studio. I believe that this mic — whether in Soundelux ifet7 or Bock Audio IFET attire — belongs on the same list of timeless and essential mics as the revered classics that we all know and love.