PreSonus Digitube

A powerful little half-rack valve preamp including three-band EQ and a digital output with word clock as standard.

The new PreSonus Digitube is a mic preamp with a variable-drive tube stage (based around a single 12AX7 dual triode) and a fairly powerful three-band EQ section. Packaged in a half-width, 1U metal case, it is powered from the included AC adaptor and is designed to accept mic, line or instrument-level signals via a Neutrik combi jack/XLR socket on the front panel. The central jack section of the socket is set for high-impedance instrument-level sources such as guitars and basses, while the XLR can accept either mic or line levels, the latter with the aid of the Pad/Line switch. Phantom power can be switched to the XLR socket, but care must be taken not to do so if a line-level connection is being used, especially as there's no phantom status LED.

Both Drive and Gain controls are provided for the preamp stage, followed by the sweep equaliser fitted with three sets of dual-concentric controls. Drive affects the degree of tube saturation while Gain simply adjusts the amount by which the input is amplified, and a 16-stage LED level meter constantly monitors the output level.

The EQ provides a range of ±12dB in three bands adjustable from 30Hz to 1kHz, 900Hz to 5kHz, and 3kHz to 15kHz. In addition, an 80Hz switch cuts low frequencies to help attenuate rumble, hum and other unwelcome low-frequency intruders. The bandwidth of the filters is preset and an EQ In button can be used to switch the whole EQ section in or out of circuit.

Rear View

The rear panel sports a single analogue output on a balanced XLR connector plus an insert point on a TRS jack, which enables another processor, such as a compressor, to be hooked into the signal path. This is particularly relevant when the digital output is being used, as it would otherwise be impossible to place anything else in series with the signal chain prior to digitisation.

The output converter is switchable from 44.1kHz to 48kHz, with switches for selecting clock rate and internal or external sync, the latter being via a word clock BNC connector. S/PDIF on RCA phono is the only type of digital output supported.

In Use

As a standard mic preamp, the PreSonus Digitube is smooth and quiet, with the tube drive adding a nice warmth up to around the halfway mark. Beyond this, some vocal sounds can get a bit messy, so it's best not to overdo it. The EQ doesn't offer anything unusual, but it sounds smooth and is more than capable of sweetening up both voices and instruments, though I felt some kind of frequency scale might have helped.

Used with clean guitars and basses, the DI input sounds clean and lively, with the tube drive lending a welcome touch of warmth and thickness, but without really getting as far as adding obvious distortion. The basic sound could be treated later with compression or effects if the occasion demanded.

I experienced no problems with the digital output and I have no concerns about the subjective audio quality coming via S/PDIF when feeding either 16-bit or 24-bit equipment, although there is no dedicated dithering option for 16-bit output.

I have no complaints about the technical or subjective performance of the Digitube, though I would have liked a phantom power status LED and frequency scales on the EQ controls. I also felt that offering the line input only on XLR was somewhat limiting, as most project studios use quarter-inch jacks wherever possible.

For anyone in the UK using a system that has S/PDIF digital inputs, the Digitube provides a sensibly-priced way of feeding in a high-quality signal, whether it be mic, line or instrument, and the combination of EQ and tube coloration makes it possible to squeeze a wide range of tone colours from this little box. Despite the small whinges about some aspects of the ergonomics, I feel the Digitube is an extremely worthwhile and versatile piece of equipment.