The Vitaliser concept has appeared in various forms since ist birth in 1988 and, as a result, has been the driving force among a wealth of professional products available from Germany's Sound Performance Laboratories (SPL). Not only did the '80s realise the birth of SPL, but it also signalled the beginnings of our fond relationship with the enhancer or exciter, as many term it.

Before the enhancer revolution took hold, engineers attempted to recreated sonically 'alive' mixes ursing the tools and techniques available at the time: compression and EQ. Many came close to producing the kind of magic that occurs within an enhancer, but it took companies like BBE. Aphex and SPL to open up the musical world's ears to the sonic delights we've since cherished from these esoteric little boxes.

Although producing a substantial number of fascinating new products (which are increasing at a furious rate), our identification with SPL proves to be with the Vitalizer. The Mk 2 is a second generation dsign, and accompanying this new generation is a totally new circuit design. New filters and extra control possibilities add to the existing parameters and, although a few names have been changed, essentially the original Vitaliser concept has remained intact.

Broken down into four major sections, the first control we encounter from the far left is the Drive pot. Unavailable on the original design, this sets the level at which the filter network begins to operate and is variable between -20 and +6 dB. Second up we have the Sound control, which is responsible for the 'colour' or tone of the bass frequencies. By turning this knob clockwise from the centre detented position, the bottom end can assume a tight, punchy feel, and by turning it in the opposite, counter clockwise direction, a softer, more rounded tone can be achieved.

Newly adopted by the Vitaliser Mk 2 is control of bass level by means of compression. As the Compressor is only integrated into the bass signal's path, high frequencies are left alone, therefore in areas of heavy compression, your recording doesn't suffer from overdulling of the top end. Threshold, attack and release are adjusted automatically, while a single knob controls the compression ratio - a very simple, but effective system.

Moving on from the Compressor, we encounter the Mid-High Tune control pot. All frequencies above the value set here, form 1 kHz up to20 kHz, are affected by a broad band shelving filter. The Process control determines how much of the output of the bass and mid-high filters is added back to the original signal, while also setting the damping intensity of dominant mid-frequencies.

Following on form the Process control is the high frequency section, with independent controls for both high EQ and relative intensity. Unlike other harmonic enhancers that add small amounts of 'musically related' high frequency harmonic distortion to the original signal to achieve their perceived transparency, the Vitaliser performs ist magic on harmonics that already exist. The high frequency EQ control has effect on frequencies at 2 kHz up.

Although the Sound, MId-High Tune, Compressor and Process controls all interact with each other, the high frequency section operates entirely independently. Also independent of the enhancement circuitry is a stereo expander, which gives the illusion of space by feeding a phase-inverted signal from the left-hand channel into the right.

A standard rocker-type power on/off switch, active and stereo expander in/out switch complete the front panel layout. On the rear, a dual pair of XLR and TRS jacks are supplied for both input and output, maintaining a balanced signal throughout.

As ist name suggests, the Stereo Vitaliser is specifically designed to be used as a stereo device. In a recording studio, the most obvious use would be to insert it across the mix or subgroups busses, yet individual stereo channels can also benefit from the creative possibilities this processor provides.

Essentially the Vitaliser works by first generating a side-chain split from the programmed material present at the input stage. From here, a complex filter network interacts with the frequency content of this signal before it's then mixed back in with the original. What's noticeable when the Vitaliser is set up and working at its optimum is a sharpening of the mid-range, a perceived increase in level of the bottom-end, and an overall brightening in the mid-to-high frequency area.

Vitaliser abuse, on the other hand, can often lead to an obvious increase in subjective noise, undefined woolly bass frequencies, and a top-end that will bite your head off. Due to the ease at which a mix can be totally destroyed by over-zealous enhancer processing, the time-honoured philosophy of 'less is more' should be adopted. To avoid enhancer artefacts, you must take care to use the Process, EQ intensity or stereo expander controls in moderation.

Anyone familiar with the Vitaliser sound will tell you that the bottom end can get a bit out of control, especially when the Sound control is set to the Soft position. By incorporating a frequency-conscious, soft-knee compressor in the bass signal path, SPL has kept the level of the bass under control, while still maintaining that all-important punch. Although the compressor is fairly limited in terms of manual control, its place in this unit is a very welcome feature indeed!

From the first time I ever used a Vitalizer, number calibration on the Mid-High Tune control pot has been perplexing. Fully anti-clockwise, the numbering begins at 2 and moves in a clockwise direction towards 1 kHz. One can only assume that number 22 refers to 22 kHz as this is a mid-high control, and 22 Hz certainly isn't a mid-high frequency. The idea behind this unusual numbering method is that the value set here determines the cut-off point at which processing begins. Therefore, by turning the Mid-High Tune pot towards the 1 kHz position, more processing will take place and the processed material will appear brighter.

The Vitaliser won't appeal to everyone, as there's a contingent of people in the industry who believe that adding enhancers of any kind to a mix distracts listeners from the music. Yet, as more and more enhancers occupy precious studio rack space, the great enhancer debate seems to be losing momentum. People are finding more creative uses for them, and this is a good thing as enhancers definitely have a place in the production tool kit, particularly the Vitalizer, with ist unique integration of amplitude-controlled phase correction, harmonic filtering, dynamic equalisation and stereo expansion.