Field Test: BLUE Microphones Robbie the Mic Preamp

Jun 1, 2005 12:00 PM, By Barry Rudolph

DESKTOP OPERATION WITH REMOVABLE TUBES

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Looking like a prop out of the 1956 sci-fi movie Forbidden Planet, Robbie the Mic Preamp is BLUE Microphones' first outboard recording product. Robbie is a single-channel, Class-A unit that can reside on your desktop adjacent to the console or a DAW's QWERTY keyboard — within easy reach. You can also rackmount Robbie or two Robbies side-by-side with an optional kit.

IT'S A BEAUTY
Robbie's aesthetically pleasing and clean industrial design features a front panel with three parts: a clear, plastic removable canopy that provides access to the ECC88 twin triode tube; a ¼-inch high-impedance (1-megohm) instrument input jack; and a smooth-working, large gain control knob. I immediately loved the gain knob, as it's the perfect height and size for my hand to rest comfortably on the desktop while “riding vocal levels” — exactly as I would do when using a mic fader channel on a console. This “lost art” has been made inconvenient by some outboard preamps and impossible by others.

When the mic is powered up, the tube's compartment — a clear plastic spacer surrounding the front panel — the gain knob's pointer and a ring of 11 frosted windows surrounding the knob glow blue. (That's right, this pre goes to 11!) I wish the ring conveyed useful information, such as the approximate setting of the 8 to 68dB available mic gain. I'd prefer that it had a calibrated scale marked in 5dB steps for the blue LEDs to back light.

The preamp's back panel has switches for power on/off, phantom power on/off, mic or instrument input, a -20dB attenuator pad (which also works on the DI input) and phase/polarity flip. Because the controls that are normally found on the front panel are consigned to the back, you should make sure that you have access to them in your studio setup. Try using a sliding rackmount tray if you rack Robbie. Also on the back are an XLR mic input and preamp output jacks, and a single Neutrik Speakon jack for connection of the line-lump power supply module.

THE INS AND OUTS
Inside the unit, the sturdy, single-sided main PC board is suspended within the metal case — sandwiched between the thick aluminum front and back panels. The front panel, with the tube mounted horizontally, uses a separate board with an edge connector that mates directly to the main board.

Robbie is a hybrid design that uses discrete transistors, metal film resistors and polystyrene capacitors — neither chips nor transformers. Class-A throughout, there is an electronically balanced, low-noise bi-polar transistorized circuit for the input stage with up to 35 dB of gain controlled by the gain knob. This feeds the ECC88 tube stage, adding another 45 dB of gain. The tube stage is followed by a low-impedance balanced output stage comprising an emitter follower acting as a current source. For the high-impedance instrument input, an amplifier comprising a pair of MOSFETs with 8 dB of gain feeds the bi-polar input.

Because the tube stage is fully powered and easily changed from the front panel, you can freely experiment with Robbie's sound. You can plug in any tubes from the 12AX7, 12AU7 or 12AT7 families, etc., with no worries. Obviously, you won't get the cleanest and purest amplification with every tube choice, but that's the whole point, isn't it?

ITS FIRST RECORDING GIG
First up, I used Robbie as a DI bass guitar. I compared a Universal Audio 6176 (no EQ or compressor in circuit) to Robbie and I found that the 6176 set to 0dB gain position went into distortion sooner than Robbie when a loud low B was played on a five-string bass. The 6176 had a little more top and bottom than Robbie, and more of a noticeable bell-like quality when playing harmonics or fretted fifths on the D and G strings. Robbie had a very slight pronounced midrange that I liked for the rock track I was working on.

Recording male vocals went well using an antique Neumann U47. For reference, I compared Robbie against the transistorized 512C mic pre's in my studio's '70s API console. With oodles of gain available, Robbie was much warmer and rounder-sounding than the API. Robbie would be the perfect preamp for smoothing out very bright mics or edgy singers on bright mics. The API, with its sharper detail and harder transients, was not as kind.

Robbie does not have a peak clip LED or a separate output level control. I connected an 1176LN compressor to Robbie's output and was able to overdrive the unit and reduce the final recording level with the 1176LN's output control. Increasing gain on Robbie gets you into tube “blooming” territory, where the sound spreads out and gets thick and gooey.

Recording female vocals confirmed my sonic opinion of Robbie: This preamp has a real “personality,” a pleasing coloration that is brought out with increased input level; i.e., as the singer or instrument gets louder.

BACK TO THE FUTURE
Robbie, living up to its neo-retro design, actually sounds like a vintage tube mic pre from the 1950s. Its modern features, super specs and reliable operation make recording everything very easy, with more than enough warm gain, low noise and ear-friendly sonics. Price: $1,299.

BLUE Microphones, 818/879-5200, www.bluemic.com.


Barry Rudolph is an L.A.-based recording engineer. Visit his Website at www.barryrudolph.com.






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