Analog Inputs (2) balanced/unbalanced ¼" XLR/TRS combo connectors Analog Outputs (2) balanced XLR, (2) unbalanced ¼" Input Impedances Mic: 1.3 kΩ; Instrument: 1 MΩ Gain 0 dB to +54 dB Signal-to-Noise >90 dB THD + Noise Solid-state stage: < 0.005% (unweighted);
Tube stage: 0.01% to 30% (unweighted) Output Impedance 51Ω Dimensions 8" (W) × 1.75" (H) × 5" (D) Weight 4 lbs.
PreSonus recently replaced the popular BlueTube stereo mic and instrument preamp with the BlueTube DP (DP stands for dual path). The unit has separate solid-state and tube preamp stages for each of its two channels. The tube stage, which is driven by a single 12AX7 tube, can be addressed in percentages or defeated by a Tube Drive control on each channel.
FIG. 1: The PreSonus BlueTube DP now offers VU meters instead of LEDs and independent tube stages that can be turned off on each channel.
The original BlueTube turned heads with its price and versatility — the unit functioned as microphone preamp, instrument DI, phantom-power supply, polarity reverser, distortion box, signal splitter, and signal amplifier for long cable runs. With the defeatable tube circuit and an improved signal-to-noise ratio, the BlueTube DP promises even more value. The street price of the newer unit costs roughly the same as the original version: about $100 per channel.
Blue on Blue
The BlueTube DP's front panel (see Fig. 1) differs from its predecessor's dramatically because of the addition of lighted VU meters, which replace the eight-segment LED meters of the original BlueTube. The Neutrik combo connectors have been moved to the rear panel, which might be inconvenient for those who want to mount the unit in a rack. Used as a tabletop or a portable unit, however, the BlueTube DP is easy to work with. The dark-blue lettering on the unit's face makes settings easy to see from a distance, and the well-spaced knobs and buttons are easy to grasp and push.
An inch-wide gap in the middle of the front panel provides a clear separation between the controls of the two channels — an improvement on the original design. On each channel a Gain knob and a Tube Drive knob anchor the controls. Above those is a row of buttons to engage phantom power, polarity reversal, a — 20 dB pad, and an 80 Hz low-cut filter. All buttons glow bright blue when engaged.
Each Gain and Tube Drive pot has subtle detents, making settings somewhat easier to reproduce when necessary. The Gain pot is labeled to indicate a range of 0 to 60 dB. (The manual says it's 0 to 54 dB.) The Tube Drive knob provides 100 percent of the circuit's effect when turned fully clockwise, and it clicks solidly into an off position when turned fully counterclockwise. Between the two knobs is a clip LED.
FIG. 2: The BlueTube DP''s rear panel hosts Neutrik combo connectors for mic and instrument input and separate balanced XLR and unbalanced ¼-inch connectors for output.
The 12AX7 tube is visible through seven slots in the top panel. The BlueTube DP's manual comes with instructions for users who want to replace a worn tube or experiment with other compatible tubes. Like some other units in its price range, the BlueTube DP does not have a power switch, and so the tube is always on when the unit's wall-wart adapter is plugged in and connected. If you keep the unit on a tabletop, use it occasionally, and are concerned about tube lifespan, then you can easily disengage the power supply from the rear of the unit as needed.
The BlueTube DP's rear panel (see Fig. 2) hosts only input and output connections. Two combo connectors give you mic and instrument inputs for channels 1 and 2, while the output section consists of separate balanced XLR (+4 dBu) and unbalanced ¼-inch (-10 dBv) outputs for each channel.
I used the BlueTube DP with a variety of pro and budget mics. I listened to the effects of the preamp on condenser mics (a Neumann TLM 103, an AKG C 414 B-XLS, and a Samson C01) and dynamic mics (a Shure SM57, an AKG D 112, and a Blue Kickball). As soon as I plugged in the first mic, it was apparent that the BlueTube DP had retained its predecessor's primary attributes; the mic pre was clean, quiet, and convenient.
Throughout a series of music and spoken-word recordings, I compared the BlueTube DP's performance with other mic pres in my studio, a group that currently includes a twin-tube dbx 386, a MindPrint En-Voice MK II (with a “dial-in” tube stage), and the solid-state XDR preamps on a Mackie Onyx 1620 mixer. Although those units have more features and higher price tags, the BlueTube DP held its own on preamp performance alone, offering up as clean a signal as any of the other preamps and a superb noise level.
The solid-state section of each channel performed exceptionally well on every mic that I connected to it, from the Neumann and AKG condensers to the Shure dynamic. (The BlueTube DP exhibited no special fondness for the Blue microphone, despite the color coordination.) My favorite vocal mics performed as expected, and the unit had more than enough headroom for the dynamic mics when I used them on guitar and bass cabinets. The highpass filter worked well on a male spoken-word vocal, and no increase in background noise was apparent when disengaging the -20 dB pad.
(Blue) Sky's the Limit
The BlueTube DP's versatility was its most attractive quality. The unit sounded particularly good as a bass guitar DI, driving a player's amp in my small live room while sending a beefy signal to my console. The clean sound was one of the best I'd recorded with this particular player, who likes to hear a deeper midrange from his amp. The BlueTube DP's heft made me curious about how it might sound on electric guitar.
Although the unit was okay for certain rhythm-guitar parts, it's much better suited for bass and keyboards. Mic and instrument pres can't give you the variety of overdrive tones that today's guitar processors and amps do. The higher range of the BlueTube DP's Tube Drive control imparted a thin and reedy distortion to my Fender Strat's bridge pickup. At lower settings, however, the control added a subtle crunch to rhythm parts.
When I returned to the clean preamp settings, I was again impressed with the overall sound of the BlueTube DP for recording clean guitar for the purpose of re-amping later. The quieter pickup combinations of my Strat were almost silent, and I could control the buzzing single-coil pickups by changing my playing position. The BlueTube DP was able to handle those signals and raise and lower them without adding noise. It also maintained the snap and bite necessary for country and funk songs without an amp.
The Tube Drive control was at its best when adding subtle, velvety shades to a female jazz vocalist's mic and rounding out the high-end content of some frosty all-digital stereo mixes that I had completed a few years before. The detents on the Tube Drive controls were helpful in applying equal amounts of subtle distortion to each stereo track.
Chasing the Blues Away
The BlueTube DP has no digital interface, as each of my other mic pres do. The BlueTube DP, however, was quieter and better sounding than two other desktop USB interfaces with mic pres that I often use for quick demo projects. The BlueTube DP's portability, sound, and low price should make the purchase of a separate, basic digital interface for your computer — especially a laptop — worth the extra expense.
PreSonus has enhanced the original BlueTube without significantly raising the price. It is a versatile and excellent sounding mic pre for the money, functions as an enhanced DI, and has the potential to add warmth to a variety of sounds that are too-cool-for-school at home or on the road.
Rusty Cutchin is an associate editor of EM. He can be contacted firstname.lastname@example.org.
BLUETUBE DP SPECIFICATIONS
two-channel mic/instrument preamp $229.95
OVERALL RATING (1 THROUGH 5): 4
PROS: Clean and quiet. Tube Drive, phase reverse, and VU meters on both channels. Stereo DI capability. Excellent value.
CONS: No power switch. Tube Drive thin and harsh at higher percentages.