MIND CONTROL

Mindprint Envoice Voice Channel

Published in SOS September 1999
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Reviews : Processor

As well as offering a high-quality mic preamp, equaliser, and valve compressor, the MindPrint voice channel can have digital interfacing added at a very reasonable extra cost. Hugh Robjohns does a spot of channel hopping.

There is now no shortage of voice channels on the market, from the budget Joemeek VC3 at one extreme, up to the latest Focusrite Blue Series Producer Channel at the other. The variation on this theme provided by the new Envoice from German manufacturer MindPrint is the provision of a valve-based compressor section, in addition to its preamp and 3-band EQ facilities, and an optional digital interface. The name of the company may well be unfamiliar to you, as MindPrint was only formed in the last couple of years, and the Envoice is the first product of theirs to reach the market (though various others are apparently in the pipeline, including a stand-alone valve compressor, the TComp, a pro A-D converter, the ANDI PRO, and a valve parametric EQ, the ParaQ). The story is that the MindPrint design team used to frequent big SSL-equipped analogue studios and moved to smaller facilities based around compact digital mixers.

MINDPRINT ENVOICE £469 pros High-quality mic preamp with line and instrument inputs. Subtle but very usable parametric equalisation. Effective and easy-to-use compressor. Valve saturation very controllable. Digital I/O option. cons Danger of wordclock howlround with digital I/O. No release-time control. summary A well-specified voice channel offering subtle but effective processing in a very affordable package, complete with optional digital interfacing.

Immediately they missed the sound of decent mic preamps, and judged the ones provided by their digital desks to be of insufficiently high quality for their purposes -- so they designed their own! However, in order to provide the closest-possible compatibility with the digital desks they were now using, they decided an optional built-in digital interface might also be welcome.

The Envoice comes in a standard 1U rackmounting box, 238mm deep, with black steel casework and a front panel finished in an earthy red colour. Its rear panel is very clearly laid out, starting with a female XLR for the electronically balanced microphone input on the extreme right (when viewed from the rear). A switch next to the socket provides phantom power, but there is no front-panel tally light to indicate when this has been activated. A balanced line input is available on both XLR and quarter-inch TRS jack socket, and the same dual-format facilities are available for the line output. An IEC mains inlet and a button to float the signal ground away from the chassis earth complete the rear-panel furniture, though on a standard Envoice unit there is also a blanking panel. This covers a bay in which the 24-bit digital output option can be fitted.

The digital option was installed in the review model, and this provides S/PDIF in and out on phono connectors, along with a pair of quarter-inch jack sockets for the input and output from the 'spare' channel of the converter -- see the 'Digital Interfacing' box for more on this point.

The front panel is a little busier than the back, but everything is logically and clearly laid out, with a control layout that mimics the signal path: input section on the left, 3-band equaliser in the centre, and compressor and output on the right. A clear window at one end of the unit allows the valve to be seen glowing warmly.

The input section features a horizontal three-colour LED bar-graph meter covering the range between -22 and +8dBu. Its traditional round LEDs poke through a silvered metal bezel which is recessed into the front panel -- an unusual effect, but pleasing to the eye nevertheless. An associated button routes the display to show either the channel input or output signal levels.

Two further buttons select either the analogue or digital input (if the digital option is fitted), and rear-panel mic or line input connections (when in analogue mode). A front-panel jack accepts input from instruments, such a

Digital Interfacing     The DI-Mod 24-bit digital interface is an optional extra which provides the Envoice with a digital input and a high-quality digital output. Normally the A-D converter operates at one of the two standard base rates of 44.1 or 48kHz, as selected by a rear-panel slide switch. However, if a valid S/PDIF signal is available at the input, the output is automatically synchronised to it. Although this is a useful facility when two or more converters need to be synchronised together, great care must be taken to avoid wordclock howlrounds. Despite the fact that the manual describes a couple of setups where both the digital output and input are connected to the same piece of equipment (such as a workstation of some kind), this scenario does not work. As soon as the workstation (or any other digital recorder) is put into record or an E-E monitor mode (Electronics-Electronics, basically an input monitor mode) its digital output carries the same clock information as its input, which comes from the Envoice. However, the digital interface in the Envoice is set up to automatically lock to an external digital input -- from the workstation in this case -- so a wordclock howlround is produced, where the workstation is clocking to the Envoice, which is clocking to the workstation! At the very least this will prevent the output from being recorded successfully, and it may produce some extremely unpleasant noises with older digital equipment. Connecting just the digital output from the Envoice to a 24-bit digital workstation works well enough and provides a very creditable sound quality. However, feeding a 16-bit device such as a DAT, CD-R or Minidisc recorder is rather less successful, since there is no provision to dither the signal down to the required 16 bits and, consequently, truncation distortion becomes evident. Since all the standard A-D and D-A chips are stereo devices, and the S/PDIF I/Os carry two channels by default, MindPrint have provided access to the analogue input and output of the 'spare' channel on quarter-inch jacks. The manual points out that this would permit a second Envoice channel to be digitised without the user having to purchase a second DI-Mod module.

s guitars, and presents them with an impedance of 1M(omega), which should not cause any significant loading effects. Plugging a source into this jack socket overrides the rear-panel inputs, but regardless of which input is in use the gain is controlled by a front-panel rotary, calibrated (arbitrarily) 0-8. Like the LED meter described above, all the rotary controls are mounted on a recessed silvered panel visible through cut-outs in the panel metalwork, and all the knobs have matching silvered caps with embossed pointers. To the right of the gain control is another pair of buttons, one of which engages a high-pass filter, while the other determines its turnover frequency (100Hz or 50Hz).

The equaliser is a parametric 3-band affair with individual band-bypass switches and associated red LEDs. High and low sections both have a 15dB cut/boost range and sweepable turnover controls. The low section spans 20-300Hz with an asymmetrical bell design, providing a higher Q (narrower bandwidth) in cut mode than when boosting, while the high-frequency section is a symmetrical bell shape and spans the range between 1.8 and 22kHz. The mid section is tunable from 100Hz up to 11kHz and has a Q control allowing the bandwidth of this mid-band filter to be adjusted from a value of 3 (a narrow 1/3-octave band) to 0.15 (a broad six octaves or so).

The next section of controls is dedicated to the compressor. A horizontal strip of LEDs forms a gain-reduction bargraph meter calibrated down to -22dB, and next to it are three rotary controls. The first of these is labelled Tube Saturation and effectively determines how hard the valve is being driven. Higher settings of this control cause more harmonic overtones to be created, thus increasing the 'richness' of the sound. A tri-coloured LED near the valve window lights green when the valve is being underdriven, yellow when it starts to saturate, and red when it's being overdriven.

The remaining two rotaries in this section control Threshold (+2 to -28dBu), and Compression (1:1 to

"Although the compressor is a little unusual to set up, it sounds very good with most material, almost regardless of its settings."

infinity:1). An adjacent button selects a slow dynamic setting that affects both the attack and release times of the compressor (which are programme-controlled anyway), making them 10 times slower and preserving more of the original dynamics in the sound. A further button inserts a high-pass filter (turnover at 300Hz) into the compressor's side-chain. This filter is provided mainly to reduce the impact of low-frequency instruments (such as bass guitar and kick drum) on the compressor.

Finally, an output level control determines the final output level from the unit, and another button (with associated LED), labelled 'Effects', acts as a master bypass, taking the signal directly from the preamplifier and skipping the equaliser and compressor sections. There's a small power switch on the extreme right of the unit.

The Envoice is very easy to set up and use, everything falling nicely to hand and working exactly as expected. The mic input is of a respectable quality, although its input impedance seems a bit on the high side. There's plenty of gain available, though, and the phantom supply proves perfectly capable of powering a wide range of top-quality condenser mics. Having both balanced line and pukka instrument inputs is useful, and the latter permits a very good degree of sustain from most of the guitar pickups I tried. The equaliser is a very musical and pleasant-sounding device, and being able to switch independent bands in and out of circuit is very handy.

Although the compressor is a little unusual to set up, it sounds very good with most material, almost regardless of its settings. The manual quotes attack and release times as 15 and 60mS respectively (150 and 600ms in slow mode), and it certainly sounds that fast, although there is also a reference in the manual to the time constants being programme-related. Having just a threshold and compression (ratio) control makes for quick and easy setting, and the compressor's soft-knee characteristic works pretty well. I would have preferred a user-adjustable release time, but that's a relatively minor niggle. The sidechain filter reduces everything below 300Hz according to a 6dB/octave slope, and it's extremely useful in taming bass-dominant material which would otherwise cause unpleasant pumping effects.

The Saturation control is situated at the start of the compressor section, which could fool the unwary into thinking it is an integral part of the compressor. This does not appear to be the case, however: a block diagram tucked away at the back of the manual reveals that the 12AX7 double-triode valve is merely used as a gain stage before the output buffer stages. The advantage of this topology is that you can use the valve to warm up a signal without also having to add compression. Overdriving the 12AX7 is smooth and progressive, producing harmonic distortion up to around 10 per cent at full throttle, along with a little HF boosting. Since the circuit is inherently non-linear, I found it paid to compress appropriate input signals fairly hard, so that they remained in the desired portion of the valve saturation curve for as much of the time as possible.

Overall, the Envoice is a particularly flattering and fine-sounding processor. If you find it doesn't immediately impress, I recommend perseverance -- its strengths are quite subtle but extremely worthwhile. The mic preamp is capable of holding its own against more costly competition, the equaliser is flexible and controllable, the compressor is responsive and relatively benign even with fairly harsh settings, and the tube saturation allows some lovely warmth or 'grunge' to be added to any signal source. Add to all that the flexible interfacing options, digital I/O, and high standard of construction, and this unit represents good value for money. It would make an ideal front end for a small-scale digital workstation, when fitted with the digital option, and would enhance anyone's basic analogue setup too.

information

£468.83; DI-Mod digital interface £117.50. Prices include VAT. Korg UK Brochure Line +44 (0)1908 857150. +44 (0)1908 857199. Click here to email www.mindprint.com