Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now


Field Test: Korby Kat 4 Tube Microphone System


In the auto world, a convertible means the ability to pop the top and have some fun, and it’s no different in the mic world. Boutique microphone company Korby Audio has released a tube mic aimed at the high end, nicknamed The Convertible, and it’s a beauty. The Kat 4 system I tested shipped with four capsules, mic body (12AT7 vacuum tube), shock-mount, power supply and cables — all inside a sturdy flight case. Three of the capsules each come delicately wrapped in a beautiful, flexible, tubular case that is fastened with a leather lace. The fourth capsule (which comes in its own wooden box) is attached to the mic body.

The removable capsules are modeled after classics, including ELAM 251, Neumann U47 and U67, and AKG C 12. Each has a number on the underside that alludes to its pedigree (251, 47, 67 or 12, respectively) and is hand-tuned and custom-designed to be as close to the original’s signature characteristics as possible, except for the U67, which has an extended top and bottom end. The power supply works with each mic, but must be set via a sliding switch on the side of the box for the type of capsule used. The C 12 and U67 offer completely variable polar patterns set via a chicken head knob on the power supply, while the 251 and U47s are fixed cardioid.

Okay, so the elephant in the room is, which 47, 251, etc., were they modeled after? After all, tube life, capsule condition, overall age and types of use all change these classics over time. For this reason, the point of this review isn’t to see if they are exactly like any of these mics I have used in the past, but if they are standouts on their own. I only thought of them as ballpark doppelgangers and didn’t hold them to any kind of close scrutiny to the original, which I think is counterproductive.

As each mic is handmade and custom-tuned by Tracy Korby himself, you have some options — you can have input into the tuning of your capsule. For instance, if you bring it home and listen to it through your rig and room and think it needs a tweak, send it back. In addition, you can have your own C 12, U67 or other mic mimicked or matched in a new Korby. If bling is your thing, you can choose custom colors or go even more high end like one client who wanted a diamond embedded in the body instead of the Korby logo.

I first used the Convertible on a Yamaha grand piano in a medium-sized room. I placed the mic about a foot over the strings and used the C 12 capsule. It sounded great, but I wanted to hear more, so I muted the audio path and quickly swapped out the capsule for the U47. It was warmer and had slightly less detail at the top, but for this track, it was perfect. The swap is a bit unnerving at first because there is no screwing involved; the capsules simply pull off and seat using four sturdy pins. There is also a guide pin, so there’s no chance of mismatching the alignment. Once you do it a few times, it’s very easy.

Next I used it as a mono room mic using the C 12 capsule, and then a mono overhead in another session with the 251 capsule. Each sounded great, with the cymbals well defined and not washy; the bottom end was full on both capsules. I quickly swapped the 251 out back to the C 12 in the overhead application and, frankly, I liked them both. This is what’s great about the system: You can quickly change your sound with very little time lost.

I next heard the 47 capsule used on a male vocal, and it was sweet with a warm bottom end and plenty of tasty top. It was compressed slightly through the dynamics section of an SSL G Series console, and that’s all it needed. It sat nicely in the track, was even over the singer’s range and perfect for this tune. Next, on a different singer who has a problematic voice that tends to be strident, the 67 capsule was perfect for the job, evening out the brashness of the vocalist and having lots of warmth and fine top end.

Lastly, I heard the 47 capsule used on a tuba played in an ensemble. The mic was about two feet above the horn, and the sound was rich and full with plenty of warm bottom end.

The Korby Kat 4 kills on a number of fronts. The implementation, fit and finish, and sound are impeccable. The most brilliant part of the system is the ability to hot-swap the capsules. You don’t know the power of the concept until you’ve tried it — all without changing your placement or moving a cable. The custom options are also nice, with the ability to alter the tuning by sending it back to the factory.

There’s also a fifth capsule available, modeled after the Sony C800G, and a separately sold FET body that allows you to get more bang for your buck. Speaking of bucks, it is not cheap to get into this system, but the quality, sound, ability to quickly change capsules and other options make this well worth the investment.

Price: $7,000.

Korby Audio, 615/383-8797,

Kevin Becka is Mix’s technical editor.