Music industry trends reveal time and again that we’re all sentimentalists at heart. The arc of our vision inevitably leans toward the past. As critic Mark Lilla notes, we’re reactionaries deep down because we are forever “firmly in the grip of historical imaginings.” And nowhere is such inclination more evident than in the pro audio business, where every third advertisement and forum thread announces new gear that can purportedly provide us a short-cut to the hallowed sounds of a Neve 1073 or a Neumann U47.

Such nostalgia, however, has an ulterior benefit: While ostensibly harkening back to the classic designs of yesteryear, some contemporary gear succeeds in providing us fresh sonic possibilities—whatever its marketing campaigns suggest. The InnerTUBE Audio U-4700 is just such a product.


The U-4700 is a multi-pattern, large-diaphragm tube condenser microphone developed through a collaboration between DSPdoctor’s Adam Brass and InnerTUBE Audio’s long-time mad scientist Stayne Alyve. InnerTUBE is known for producing the much-admired Atomic Squeezebox compressor/limiter, a widely-popular U87 tube retrofit, and more idiosyncratic creations like the MM-2000 (a tube LDC seated in a Maglite body) and their Gefell UM70/71 update, which comes housed in—wait for it—a metal beer bottle.

The U-4700 boasts a traditional-sized body, a three-layer mesh head grill, and a premium, American-made, dual-diaphragm K-47 capsule. Without knowing too much about the secret sauce Stayne employed in the mic’s production, I can attest that it sports a completely novel, custom circuit designed to highlight some of the K-47’s time-honored benefits, such as a useful proximity effect, full frequency response, and presence in the 3-5 kHz range. Stayne’s choice of a rather unconventional tube (the 6N23P/6H23P), and the manner in which it is powered, also have some role in the mic’s considerable mojo. The build-quality of the mic, power supply, and shock-mount are impressive, and the whole package comes in a sturdy suitcase.


Engineer and mixer Curtis Edwin Plummer and I auditioned the U-4700 over several days at Curtis’ Dragon Ship Studios. All sessions were run in ProTools 12, utilizing Apogee Symphony (Version 1) converters at 96k. We’re fortunate at Dragon Ship to have several gold-standard preamps, and we used the U-4700 most often with either a D.W. Fearn VT-1 or NPNG DMP-2NW. The former provides uncommon lushness, while the latter affords an almost preternatural, three-dimensional signature, and it’s rare that one of the two doesn’t exceed expectations. We also tested the mic with more common hardware—an API 512c, Neve 1073LB, and Focusrite ISA—with favorable results. Occasionally, we patched in a compressor during tracking (a Distressor, Retro Doublewide, or Inward Connections Brute), but we avoided EQ-ing “to tape” in all instances.

Between the two of us, Curtis and I have recorded a few original 47s and a number of modern clones. We’ve used or owned models from Peluso, Pearlman, Mojave, and Bock—all of whom produce fine microphones in the same general price range as the U-4700. We have admittedly less experience with what I’d call the “upper tier” of contemporary 47-type mics, such as the Wunder, Lucas, and Telefunken, but given those mics’ greater expense, they seem to inhabit a different market than the InnerTUBE. Curtis’ Pearlman TM-1 and Gefell UMT-70S (an entirely different, but much-loved utility mic around the shop) provided immediate points of comparison throughout our sessions.

While our tests logically focused on vocals, we also employed the U-4700 on drums (mono overhead, room, and front-of-kit applications), piano, acoustic guitar, electric guitar, and sundry percussion, like tambourine and shaker. In all instances we were impressed—and in some moments ecstatic—with the mic’s sonics and versatility.

U-4700Our first take, a scratch track of a Guild F50 acoustic (in omni) produced an epiphany from everyone gathered in the control room, and a quick affirmation from Curtis: “That’s the best acoustic guitar sound I’ve ever had in here.” The U-4700 deftly captured the Guild’s inherent woodiness and fundamentals, while smoothing over any excess pick or string noise. In drum applications—where we sought a robust, full-kit representation—the mic proved detailed and balanced, adeptly reproducing a wide frequency spectrum while deemphasizing any stridency from the cymbals. As a heavily-compressed room mic the U-4700 provided the kit considerable energy with no harsh artifacts.

On electric guitar speakers we customarily pair a ribbon and condenser—often an AEA R92 and the Gefell. Swapping in the U-4700 for the UMT-70S resulted in a rich sound that didn’t sacrifice the clarity and cut normally afforded by the Gefell, and the InnerTUBE handled the high SPL flawlessly. On mono piano, positioned slightly behind the hammers, the mic brought out the immediacy and sweetness of Curtis’ ’65 Steinway B.

Our initial test vocalist Thomas Mcdonald possessed a gritty tenor reminiscent of the Hold Steady’s Craig Finn, with a little bit of Elvis Costello, and a tendency for unwelcome sibilance. In cardioid, about a foot back, the U-4700 sustained all of the detail of his performance while adding a smooth, natural, top-end sheen. The graininess that attends the upper registers of some modern condenser microphones (of a certain nationality) was entirely absent, and while Thomas is sometimes a candidate for aggressive de-essing, none was required. As Curtis said, the mic seemed “voiced properly for recording in digital”—achieving a “vintage mic sound, like it’s being printed to tape, but it’s not.” At no point did we detect the brittleness that I’ve heard from some other contemporary 47 clones. That’s not to suggest the mic is dark—indeed, there’s ample air on tap.

From a broader production standpoint, I also noted how well the vocal simply sat in the developing arrangement—without EQ or other massaging. Sure, a good performance, in a good room, with a stellar mic-preamp helped, but the utility of the U-4700 allowed us to move forward, confidently and quickly, with the session. This is not an unimportant detail.

We also used the U-4700 on a variety of sources with local artist Bryan Knispel (of progressive-rock band Divine Ratio) and during a demo of an acoustic-driven ballad with the roots-rock band Roosterfoot, featuring lead vocalist Seth Stainback. An example track from that session is available on our SoundCloud page, here.

So why another U47 clone? Well, the U-4700 isn’t one. The list of contemporary microphones purporting access to the U47 magic is now awfully long, and considering the reality that most of today’s recordists have little practical experience with the Neumann of legend—let alone the in-house technical folk to support its care-and-feeding—I do wonder sometimes about our vintage appetite and the marketing frenzy that supports it.

Ultimately, the U-4700 is fantastic piece of modern kit. Whether it achieves a faithful resemblance to history’s most famous microphone is in the ear of the beholder, so to speak—though I think the question is largely an irrelevant one.

For contemporary production, regardless of genre or source, the U-4700 is a wonderful tool, at a very reasonable price-point. And such criteria, devoid of nostalgia, ought to be our guide.

The InnerTUBE Audio U4700 is available through DSPdoctor, here. $2850.