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Ross RX-NR4

4-Channel Noise Reduction By Derek Johnson
Published April 1995

Derek Johnson looks at a cost‑effective way of cutting down the noise in your studio.

Ordinarily, one would have to make a distinction between a noise reduction unit and a noise gate. They both deal with noise in different ways: a (single‑ended) noise reduction system filters out the overall noise content of a signal, while a noise gate listens to a given signal and shuts it down when it falls below a pre‑determined level (the threshold), eliminating any undesirable noise that might be present. Gates are particularly useful for cutting out unwanted noise present on a tape track or generated by an electronic instrument, such as synth hiss or digital noise, guitar amp noise, lip smacks and so on, when the wanted musical signal isn't active.

Essentially, Ross' RX‑NR4 falls into the latter category, in that it provides four channels of noise gating that feature all the basic facilities for doing the job. It comes in a traditional 1U rack package, and is thankfully provided with a built‑in power supply. Each channel offers a threshold knob (‑50dB to ‑10dB), a ratio control (1:1 to 1:8), and a decay control. These controls allow you to set up each gate to respond in an accurate and musical fashion: for most applications, you don't want to lose the main attack of the signal, nor do you want the tail end to be cut short. All four channels also feature an in/out switch and a noise reduction indicator LED. Rear connections for all four channels are on jack sockets.

As a noise gate, the RX‑NR4 lacks one or two sophisticated features, such as side‑chain access or side‑chain filtering, offered by other units. However, each channel also features a switchable low‑pass filter with a range of 200Hz to 5kHz, which allows each circuit to behave more like a noise reduction unit. Given that most of the noise that we want to get rid of (hiss and so on) tends to be above the 3kHz mark, this feature is strikingly effective. When the filter is switched in, it allows the gate itself to work only on the frequencies above the frequency selected, and behaves in a similar way to a side chain filter on a more sophisticated gate.

In Use

Using Ross' noise gate is simply a matter of plugging it in and adjusting the controls by ear. Typically, each channel will be plugged into the insert points on mixer input channels or master stereo outputs, or in line with tape track or instrument outputs, if your mixer lacks these features. Adjust the threshold, ratio and decay knobs by ear, and switch in the filter to cut out any annoying hiss if needed. During the review, I tended to assign two channels to my main mix output, with the other two channels used for problem synths or effects. I have an old reverb that is very noisy, and an extra two channels of gating/filtering allowed me to use it without adding bags of hiss and strange digital burbles to my mix. Keep in mind that if you set up the decay to close too fast and the Threshold to open too slow, you may get chattering — you'll know it when you hear it. Having said that, with the decay set to 'minimum', and with a reverb patched through two channels, a highly convincing and aggressive gated reverb effect is possible.

Sonically, I have few complaints: when noise is being shut down, nothing leaks out — with no music playing and with all my levels turned up, nothing, not even the old reverb I mentioned earlier, breaks through. I found the controls to be a little fiddly, and for me the layout is a little unintuitive: when working quickly, and perhaps in less than ideal lighting conditions, it's quite easy to tweak the wrong control. But I would take into account the unit's low price and judge accordingly. The same goes for those of you that may bemoan the lack of side‑chain access (and I miss the ability to link channels for true stereo operation).


At a little over £50 a channel, it's hard not to approve of the Ross RX‑NR4. I can think of few more affordable ways of adding extra noise gate/reduction channels to your system. If you need side chain access and more comprehensive facilities, then look elsewhere, and be prepared to spend more money. But if you want four channels of affordable and easy to use noise gating, the NR4 deserves consideration.


  • Four gates with noise reduction for little more than £200.
  • Easy to use.


  • Pairs of gates not linkable, for stereo use.
  • No side chain access.
  • Controls a bit fiddly.


An unpretentious device that delivers what it promises at an attractive price.