With increasing usage of digital recording systems, there's a heightened awareness of unwanted noises and hiss. Bob Dormon finds an answer in the Behringer SNR 2000 Denoiser

I'm sure that anyone involved in sound recording will have a few tracks tucked away in a murky archive, marked with the mental note 'if only...'. If only there hadn't been so much noise on the tape, more often than not. Those who have graduated to digital multitracks will also have a number of four-track favourites with a vibe they'd love to revive.

Yet the lure of retro usually stops short of piecing together a performance from a portastudio original. Once you begin to climb the ladder of music technology, revamping rather than reviving is the order of the day. Even at the other extreme, digital reproduction will show up the shortcomings of sonically challenged equipment. Buzzy beatboxes and sizzling synths are going to be far more noticeable, as they won't be hidden by tape hiss or masked by noise reduction systems.

In both cases, if there's noise present, you'll want to do something about it. Behringer certainly agree, and the SNR 2000 Denoiser is their way of telling unwanted signals to 'hiss-off'.

Overview

The Denoiser has been designed with this purpose in mind, but offers far more flexibility than an off-the-shelf preset noise reduction system from Dolby or dbx. All of these have their merits, yet the Behringer can be applied to a wider variety of lamentable sonic scenarios.

In short, the SNR 2000 has two processing sections, an expander and a dynamic filter. The expander can be used to act as a noise gate, while the dynamic filter has an auto setting to derive its action from the input signal.

The two channel device can be set to stereo link mode, so that processing is applied equally to both sides. Each channel has two 8-segment LED meters. These relay gain reduction (in red) and the cutoff frequency (in yellow). The two processing sections can be used independently, so that you can switch in either or both.

The unit has all the usual Behringer hallmarks; white legends on a black background. Each channel has an overall bypass switch, plus one each for the two distinct processing sections. The dynamic filter has an additional auto switch, which affects the release time and cut-off frequency. Switch it to manual, and two dedicated knobs alter these functions, together with the sensitivity control. Similarly, the expander has three knobs to vary the threshold, release time and expansion ratio.

The back panel is simplicity itself, offering balanced 1/4"jack (TRS) and XLR connectors. Only inputs and outputs are catered for, as there is no sidechain access. Mains is supplied through an IEC socket, and Behringer provide a cable sporting a US-style moulded plug on the end. Thanks guys, it's really useful... not.

The manual has quite a number of suggestions for applications of the denoiser, and also gives a brief explanation of the various methods employed to tackle noisy signals. Anyone unfamiliar with this kind of 'single-ended' device (and noise reduction in general), will find this basic introduction helpful.

The term single-ended means that you can apply it as and when required. With conventional noise reduction systems you need to record and playback with the appropriate processors, to enjoy the benefits. This is because two different processes are applied at each stage. With the Behringer, you can apply it at any stage, as you might with a noise gate or an effects unit.

In use

Having the expander and dynamic filter sections separate is very useful in setting up the Denoiser. It makes hearing the processing action a lot easier to evaluate. After all, we're dealing with noise here, and in general it's (hopefully) not going to be the loudest sound you're going to hear.

Nevertheless, you'll want to make sure that 'real' sounds don't suffer from the effects of over-enthusiastic tweaking. This is where the sensitivity control on the dynamic filter comes in to play. The range from -50dBu to +10dBu allows the filter to engage on extremely quiet material. Yet for tapes, you'll need to crank this up to around +10dBu in order to get a response.

The cut-off function works from 6kHz down to 800Hz. The manual suggests that having set to 800Hz for the majority of cases is the most effective. Basically, as soon as you've set an effective sensitivity setting, then the cut-off frequency will attenuate (or filter out) noise in, starting at its current frequency setting and all those frequencies above it.

It's a sophisticated low pass filter, enabling low frequencies to pass through unaffected. You might think that everything would end up sounding muffled, but not so. For Behringer have 'broken new ground' (perhaps they've been to Japan recently) with their TAC (Transient Attack Control) circuitry. Far from assaulting vagrants on the Underground, TAC tracks the signal response using peak detectors, so that fast transients – such as percussive sounds – can be preserved rather than squashed. Altering the filter from 6kHz down to 800Hz has the effect of dampening the background noise from sounding like tyres on a wet road, to rain on a garage roof.

If you introduce the expander into the signal path, then you can mute out the noise in the quiet passages altogether. Turning up the ratio control increases the severity of this action which, together with the threshold allows you to gate your signal. At the other extreme, you can use the expander to subdue low volume sounds, and use the expander's release control to govern the recovery speed of this effect. The expander's IRC (Interactive Ratio Control) circuitry can also be found on the Composer, and a more detailed description can be found in the review of this device in the December 94 issue of The Mix.

Performance

I didn't have to look too far to find candidates for denoising. First up, an old FM radio recording. As noise covers an extremely wide frequency range, the hiss could be contained to a gentle roar in the background, as the lower frequencies remained. On its own, the dynamic filter weaved its way through the music, doing its best to retain the colour of the original material while the signal levels rose and fell.

Bringing in the expander helped considerably. The overall effect was more akin to damage limitation than elimination. Nevertheless, the Denoiser did exactly what its name implies. Initially, setting it up can involve a search for perfection, but it's worth putting the unit into bypass occasionally, just to remind yourself of how bad things are. It's then that you begin to realise that perfection may not be possible, but what you get is an admirable compromise.

If you want to be more creative, then you can use the filter section to soften sounds that are too bright. I put a few drum samples through it, and not only managed to gate out the residual hum, but also to alter the crispness of the hi-hats, and the snappiness of the snare. Using the Denoiser in this way could also be useful for toning down over-bright mixing. In fact, wherever there's a signal, you can entertain the thought of using it. Street interviews could benefit from lightly reduced background noises, and tape-to-tape copying is an obvious choice, as well as groggy camcorder audio.

Verdict

Initially, you'll need to put in an extra bit of effort to get the best out of the SNR 2000. It's not difficult, it just demands a bit of care. After all, the result you get out of it will be determined by your skill in setting it up in the first place. If you think the expander would be an additional gating alternative, then be aware that it can respond slower than a gate would on low level program material, yet perform well on louder sounds.

The dynamic filter section may not impress you immediately, but once you get used to its operation, particularly on quiet noisy recordings, you soon realise that it's making a decent effort at a dirty job. For me, the only real shortcoming was that there was no way of dealing with low frequency noises such as mains hum. Perhaps if a future model had a low frequency cut-off switch, somewhere around 150 to 70Hz, then noise could be addressed from all angles.

As home recording plays an increasing part in a musician's work, the need for devices like the Denoiser is growing. Phil Collins did most of his last album at home (see Home & Studio Recording December 93) and his tracks were denoised using a Sonic Solutions system, before graduating to the album. However, Sonic Solutions is about thirty times the price of an SNR 2000. But it's nice to know that at both ends of the scale, there's always someone ready to take the hiss.