Mindprint DI Port

Martin Walker looks at a handy half‑rack unit which could provide an ideal front end for your computer‑based recording system.

Many people are now recording to 24‑bit hard disk recording systems, and are therefore happy to do all their audio processing, including equalisation and compression, within the digital domain. While this is certainly a very flexible way of working, the quality of the results will inevitably depend upon the quality of the preamplification and A‑D conversion which initially transfers the audio from the analogue to the digital domain. As the quality of the built‑in preamps and converters within recording workstations and soundcards often leaves a lot to be desired, there is consequently an increasing demand for stand‑alone units offering such features.

MindPrint have added to this expanding market with their DI Port, which provides stereo preamplification and 24‑bit A‑D conversion, along with 48V phantom power. It also includes a stereo D‑A converter and various options for latency‑free monitoring.

Half‑pint Port

Like the rest of the MindPrint range, the DI Port has a black half‑rack case with a maroon front panel sporting black and chrome knobs. On the left‑hand side of its front panel are the analogue inputs: a pair of Neutrik combi‑jack sockets that let you plug in either an unbalanced line signal, using the inner quarter‑inch jack, or a balanced mic signal, using the outer XLR socket. There is a global switch for phantom power. Another switch selects between using the front‑panel sockets or a second pair of unbalanced phono inputs on the rear panel. Each input channel has its own rotary gain control (providing up to 53dB gain), a green LED to indicate the presence of signal, and a red Peak LED that illuminates 2dB below clipping.

The S/PDIF digital connections are on the rear panel — both Toslink optical and phono coaxial inputs are provided. If the associated Master/Auto button is in Master mode, the DI Port uses its internal clock at a sampling frequency determined by another switch adjacent to it, while in Auto mode the sample rate is locked to that of the digital input. There is a useful red LED in between these switches to indicate that a valid digital input signal is being received. One slight problem for users of 16 or 20‑bit recorders is that there is no facility for dithering the digital output to lower word lengths, so these users would be unlikely to be able to record digitally from the DI Port without incurring truncation artefacts.

The monitoring section has an unusual rotary Mix control, which allows you to listen to a combination of the signals at the analogue and digital inputs. Next to this knob is a rotary Volume control which feeds three stereo monitor outputs — a pair of unbalanced phono sockets and a stereo quarter‑inch jack socket, both at line level on the rear panel, together with a front‑panel quarter‑inch stereo jack socket providing up to 300mW into 33Ω for headphones. The D‑A converter outputs emerge via a pair of unbalanced phono sockets and a socket for the supplied 12V AC wall‑wart completes the rear‑panel connectivity. The review model was supplied with a two‑pin mains connector, but I would hope that the UK version ships with a three‑pin one — perching it atop a shaving adapter does not make for a secure and reliable connection!

Mind Matters

With the Gain control set to minimum, the A‑D RMS background noise at the rear input measured ‑103dB when recording at 44.1kHz in Master mode — a little higher than that of the Lynx One, but extremely good nevertheless. However, when clocked in Auto mode from the Echo Gina, deteriorated a little to ‑99dB.

The converters used in the DI Port are exactly the same as those in the Gadget Labs Wave/8•24 and Lynx One, and are capable of excellent performance. Auditioning them against my Echo Gina soundcard showed that the DI Port's converters had a top end which was very slightly more natural and transparent, while the bass end was smoother and more controlled. The background noise was significantly lower, and I also noticed a subtle improvement in stereo detail when I ran the DI Port from its internal clock, rather than using that of the Gina, which suggests lower jitter. The mic preamps also sounded very good, and the headphone output provided quite enough level for my 60Ω Sennheiser headphones.

The MindPrint DI Port would come in handy not only for studio digital recording, but also for location work, given its monitoring and headphone outputs. Overall, this is an extremely useful little box, and only those who need 16 or 20‑bit digital output or fully balanced I/O need look elsewhere.