PreSonus Blue Tube Affordable Mic Preamp with Tube Warmth and Features Galore

PreSonus Blue Tube

An affordable mic preamp with tube warmth and features galore

By David Ogilvy

PreSonus Audio Electronics seems it’s out to prove good things do indeed come in small packages. First came the Blue Max Smart Compressor, a great-sounding half-rack unit unique in its class for providing compression presets for a variety of applications. Now PreSonus is filling up the other half of the rack tray with the Blue Tube, a stereo microphone and instrument preamp with a hybrid tube and solid-state circuit design. The unit utilizes a single 12AX7 tube and independent drive knobs for dialing in the desired amount of tube “warmth.” At less than $100 per channel, the Blue Tube also lays claim to being the least expensive tube mic pre on the market.

Realm of the Senses

The PreSonus Blue Tube is a good-sounding, well-featured, and very versatile microphone preamp/DI. A separate Drive control lets you add tube distortion to taste—or leave it out altogether (click image).

Despite its diminutive size and low price, the Blue Tube is well built and well featured. It uses Neutrik Combo connectors to provide two XLR mic inputs and two 1/4-inch high-impedance instrument inputs on either side of its blue, brushed-aluminum front panel. Controls are laid out in mirror image (from left and right of center), with each side providing a Gain knob and Drive knob, switches for polarity reverse, and a 20 dB pad. In the center is a global 48V phantom-power switch. All five switches are push-button style, and the four knobs are continuously variable. Each channel also provides an eight-segment output meter, with green LEDs at –28, –14, –9, –3, 0, and +3 dBu, a yellow “caution” LED at +9 dBu, and a red overload indicator at +18 dBu.

The Blue Tube’s enclosure is very sturdy, and the knobs and switches have a nice feel. Although there isn’t a dedicated power switch, a red front-panel LED indicates power on when the unit is plugged in through the included wall-wart power supply. (Using an external transformer is one way PreSonus could keep internal noise and costs down.)

The Blue Tube’s rear panel provides XLR balanced and 1/4-inch unbalanced outputs. Each output has its own amp, allowing for simultaneous output from the two jacks on each channel. That is useful for sending a signal to two places at once, such as to an amplifier and a mixing board.

The Blue Tube’s well-written manual explains that each channel contains a dual-servo gain stage—a design that eliminates the need for capacitors and lets the Gain knob “boost the desirable signal without increasing unwanted background noise.” The manual also discusses optimum settings for various applications, and even encourages the user to experiment with tubes other than the provided 12AX7.

Reprinted with permission from

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