“This cute little box is dual channel microphone and instrument preamplifier. At UK165 it is firmly in the budget sector and the price is all the more remarkable for a tube device. The housing is approximately half a rack space wide — PreSonus has designed a rack converter kit but has not manufactured this yet. The case is very shallow, the whole thing is fairly light, but it seems well built, with attractive curved aluminum colored finished sides with fins, and a matching front panel that continues part of the way around the top and bottom of the case.

The remaining case is black painted steel, the top features a grill through which the tube is visible, and there are indentations top and bottom for the supplied rubber feet to adhere to and, presumably, for multiple units to stack onto. I imagine this unit is most likely to be used on a desk rather than in a rack. Power comes from a wall-wart of average size but more than average weight that puts out 16V. The lack of a power switch would, I imagine, be a nuisance should you ever rack mount a pair of these.

The BLUETUBE DP replaces the original BLUETUBE model, which was similar in many ways. The most noticeable difference is the addition of the circular VU’s in place of the combi XLR/Jack inputs (for microphone and instrument respectively) that have been located to the rear. Also on the rear are outputs in the form of separate (rather tight fitting) female XLR and unbalanced Jack sockets for each channel. When plugging in the DC connector, rather than the slow change to an orange glow you might expect from a tube, there is a rather intense red LED light immediately shining from behind the valve, presumably for that famous magical LED warmth!

I suspect the main reason for this is to disguise the rather weak natural valve glow, which is the result of powering the valve with merely 16 volts. When powered up the VU’s yellow background is magically illuminated with blue light. The front panels VU meters are fine but, like the internal LED, are undoubtly a fashion choice — simpler LED meters may have been better. However, rear inputs keep things neater.

Each of the front panels eight pushbuttons lights up blue when pushed in. And guess what, the knobs are painted blue… They must have really thought hard about the color of that internal LED, finally deciding that a blue-glowing tube might have worried some users! The knobs are for Gain and Tube Drive for each channel. Gain range is legended as being zero to 60db with 15, 30, and 45 indicated at 90-degree points on the scale. Although the knob goes past the 60 mark, the spec sheet claims only 54dB of available gain, and indeed there seemed to be considerably lower levels seen out the output than high-end units set to roughly similar indicated levels.

For most situations and with most microphones there is plenty of gain available, although when interfacing low output microphones with professional equipment you very occasionally find that there is just not quite as much gain as you might wish for. The knobs have a rigid barrel and multiple-dented feel, despite there diminutive size, they are pleasant to twiddle. The Tube Drive knob varies from that of the original model in that it has a click off position at the left. This eliminates the tube circuit — hence the ‘Dual Path’ in the name. This knob can then be cranked to provide extra harmonics and distortion from the tube circuit. Between the two knobs on each channel is a clip LED — headroom is adequate and the noise floor is very low, even in tube mode. This usually lit before the signal level strained the professional +4 converters I was interfacing with. The front panel buttons comprise 48V phantom power, polarity reversal, Pad (-20dB) and a useful 80Hz high pass filter for each channel. As a microphone preamp I compared it directly with a couple of far more expensive models, and the BLUETUBE stood up very well. With the tube circuit off, the tone is very natural and uncolored. It sounds clean, if slightly less detailed than more expensive units, but these models were costing about ten times the asking price of the BLUETUBE DP. Switching on the tube circuit, at the lowest drive setting there is a low-end bloom added to the sound along with a softening of the tone.

As the Tube Drive is cranked, a slight fuzziness is gradually added, until at full-tilt there is an unsubtle distortion. This probably isn’t desirable for most circumstances when using the microphone preamp, but lower tube drive settings certainly add warmth and extra harmonics that might be beneficial for certain overdubs. Using the instrument input, there is an enormous amount of gain available, far more than needed for any guitar. However, this lacked some of the thickness and midrange detail of high-end instrument preamps. Subtle amounts of Tube Drive enriched the signal, although full drive generally sounded fairly horrible and a bit ‘hairy’ — I actually preferred cranking the Gain full up to overload my converter’s analogue input for full-on fuzz!

The old model proved something of a favorite for guitarist wanting a touch of valve magic. By inserting the BLUETUBE between guitar and amp, a useful subtle extra bit of drive and crunch can make for a very agreeable tone, and a little extra gain driving the amp’s input can be useful. This was the only situation where full Tube Drive sounded good! I suspect it may be worth experimenting with a better replacement tube, depending on the main application…

The DP is a good value, well made, and boasts surprisingly fulsome sounding microphone preamps that stand up well to comparison with more expensive units.”

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