Digitech VCS1

The VCS1 goes for the best of both worlds, featuring a valve for warmth and character, and solid‑state technology for level control. Hugh Robjohns finds out what the combination has to offer.

The VCS1 is a dual‑channel (but stereo‑capable) multi‑function dynamics processor from the American company Digitech. It's a well‑specified, well‑equipped unit, incorporating a dual‑triode valve in the output circuitry to give that classic warm tube sound, and the latest in solid‑state VCA technology for accurate and clean level control. The VCS1 is aimed at both the recording studio and the live sound rig, and has been designed to be easy to use and to provide the operator with very clear information about the state of its dynamic control activities.

A full complement of dynamics processors is provided for each channel, including a compressor, peak limiter, noise gate and de‑esser. These all operate through a single VCA in each channel, whose control signal is derived from the sum of the control voltages produced by each of the individual dynamics processes, all working in parallel. This topology avoids the inherent problems of serial processing, such as whether to compress before the noise gate or after, and where to place the de‑esser. The parallel processing arrangement employed by the VCS1 means that each section is working directly on the raw input signal, which makes it considerably easier to set up, and offers a much more reliable and predictable sound quality.

The Box

The VCS1 is a 2U‑high, 19‑inch rackmounting box, measuring a fraction under six inches deep. The unit is supplied with suitable bolts and washers for mounting in a rack (why do so few manufacturers supply such essential fittings?) and a decent IEC mains lead with approved moulded plug.

The rear panel is festooned with connectors — four A‑type sockets and two XLRs for each channel. The input is equipped with an XLR and A‑type jack, both electronically balanced, although the jack socket is happy to accept unbalanced signals too. A push button determines the nominal operating level for the input (+4dBu or ‑10dBV) and the output level can be adjusted over a very wide range, by a front‑panel control. The output signal is presented on an XLR and A‑type socket — again, both electronically balanced. Side‑chain access is provided through a pair of normalled jack sockets, operating at +4dBu, but unbalanced this time. On the extreme left‑hand side of the rear panel is the IEC mains socket with integral fuse holder.

Front‑panel layout is simple and logical, visually dominated by two large, circular, backlit VU meters. The panel graphics are clear and restrained, with white and green text on a black background, and the operational controls are sensibly grouped for the two channels, the extreme right‑hand end of the panel hosting the common facilities of a stereo channel link and the mains power switch.

Controls

Each VCS1 channel features 10 rotary controls and four chromed toggle switches. To the left of the VU meter are a pair of output level controls, clearly identifiable by their oversized knobs. The upper control of the pair sets the final output level from the channel, with up to 20dB of make‑up gain available, and the ability to reduce the signal all the way down to silence, if required. A centre detent identifies the unity gain position, and a red LED just above the knob illuminates when any point in the signal path (pre‑VCA, post‑VCA but pre‑valve, and post‑valve) is at 3dB below clipping. The lower knob of the pair determines the drive level into the parallel‑triode valve stage, and is calibrated from ‑20 to +20dB with a detent at the unity gain point. The valve in question is the 12AX7A (better known in the UK as an ECC83), manufactured in Russia. Digitech emphasise that the valves are all hand‑tested and ‑graded, and the circuit design employs a fully regulated 235V anode supply for good signal‑to‑noise performance and transient response. As might be expected, boosting the Tube Gain control enhances the even‑order distortion products, giving a range of effects, from a subtle but audible warmth to an obvious bite.

If the VCS1 is switched into stereo‑link mode, the controls associated with channel 1 also determine the settings on channel 2, the controls of the latter becoming inoperative. All, that is, except for the output level controls which, strangely, stay completely independent.

The remaining operational controls are arranged on the right of the channel's VU meter in two parallel rows of four smaller knobs, with the four toggle switches sitting neatly below them. The lower row of knobs are all associated with the compressor, while the upper set account for the noise gate, de‑esser and limiter.

The first toggle switch determines the signal displayed on the VU meter, which may be gain reduction (up to ‑30dB on the meter, with 0VU indicating no gain reduction), or the output signal level, where 0VU represents an output level of +4dBu. If the channel section is bypassed (with the last toggle switch in the row of four), the VU meter shows the input signal level. The bypass function removes everything from the signal path except for the input and output buffer circuitry (the VCA, valve, output level control and everything between are taken out of circuit).

Compressor

The compressor is provided with controls for Threshold (‑40 to +20dBu), Ratio (1:1 up to infinity:1), Attack time (0.1 to a leisurely 200ms) and Release time (50ms to three seconds). Just above the threshold control, a pair of LEDs show the compressor's operation. A green LED illuminates if the signal is below the threshold and a red one indicates when the signal exceeds the threshold. These LEDs are extremely useful, because although the VU meter can show gain reduction, without the LEDs the user might not know whether the meter reading was caused by the compressor, limiter, noise gate or de‑esser.

Both hard‑ and soft‑knee compressor characteristics are available, selected by the toggle switch directly below the Ratio control. Changing the setting has a clearly audible affect on the nature of the compression. The scale around the threshold control is calibrated for the hard‑knee setting and under‑reads by about 10dB when in soft knee mode, as detailed in the well written and helpful VCS1 manual.

The Attack control operates over an unusually wide timing window, but this allows some very powerful effects to be created, particularly on percussion and bass guitars, where slow attack times allow the transients through but regulate the level of the decay or room ambience. The Release circuitry features the so‑called 'True Logarithmic Compression', which is claimed to match the response of human hearing for a more natural and pleasing effect. A toggle switch below the Attack knob engages an automatic timing system, setting attack and release times according to the nature and dynamics of the input signal.

Alternative Dynamics

The upper row of control knobs handles the combined functions of noise gate, de‑esser and limiter. The first two controls set the Threshold (‑60 to +20dBu) and Attenuation level (0 to ‑60dB) for the noise gate. Operation of the gate is indicated by a green LED above the Threshold control. The third knob adjusts the amount of attenuation applied by the de‑esser (0 to ‑28dB), which is sensitive to frequencies above 4.5kHz. Strong signals above this frequency will trigger broad‑band gain reduction according to the setting on the control. Its activation is indicated by a yellow LED.

The last knob controls the separate peak‑limiter, which has a Threshold calibrated between ‑8 and +24dBu, (labelled 'Off' at the extreme clockwise point). Once again, an LED is used to indicate when the limiter is active.

Studio Test

The VCS1 is a doddle to set up, with its clear and simple controls and handy LED indicators identifying which dynamics sections are operating at any time. The specifications for the unit are extremely good, and my auditioning confirmed that this is a high‑quality product, both mechanically and electronically.

The range of sounds that can be obtained from the Digitech is impressive for such a modest unit, and I found I could easily achieve the required level of dynamic control in most situations. The inclusion of the valve stage allows an extra dimension of controllable coloration to be introduced, and I found this to be particularly effective on vocals and other harmonically simple instrumentation.

The VCS1 is certainly not the last word in transparent compression — or in accurate gating or de‑essing, for that matter. The absence of attack and release time controls on the gate restricts its usefulness slightly, as does the lack of a tuning control on the de‑esser, but bearing in mind that this is a multi‑function, general‑purpose machine, these shortfalls can be easily overlooked and barely detract from its overall value.

While there are many alternative and more specialised dynamics units on the market which might make a better job of any individual function, the VCS1 provides a well integrated combination of useable and competent processes. It would be a worthwhile unit to install in your rack — whether for the studio or a touring flightcase — and the compression section alone is worth the asking price. The VCS1 is an attractive and versatile unit which I'd place towards the top of my wish list.