Within its Rane Digital range, RANE offers us two units with four channels each, dedicated to handling two of the most important tasks both in the studio and live: "compressing" and "gating." C4 - Quad Compressor/Limiter
The C4 is the model Rane offers for everyday work in the studio or live, where we need a reliable unit that gives us extensive control over each of the channels being processed.
To do this, it offers four channels of compression with de-esser and limiter in just two rack units, which, as I said, gives us great control over the dynamics of the signal being processed. Remember that a compressor can be used mainly to: reduce the dynamic range of vocals or other instruments that exceed the playback or recording capacity; prevent peaks or distortion in live sound or recording; smooth out and "balance" instruments, such as bass, that have a wide dynamic range and level variations from one string to another; reduce sibilance; produce a stable recording level for broadcast, etc.
Before going into a more in-depth analysis of this unit's response, let's go over its technical features and the operating options it offers.
Let's start with connectivity. We find that we have an independent input and output for each channel, with balanced XLR connectors linked to balanced jacks. It also has four jacks for externally controlling the side-chain of each channel (we will explain this below).
As for the controls, the first thing that stands out is how we can use the side-chain (we could say the side-chain is like the "hand" that controls the volume: when it detects an input signal, it examines it and sends a control message to adjust the gain of that input signal, according to the chosen settings). The side-chain has its own path that lets us choose whether to control it with an external signal via the corresponding input (for example, we can use as a source a signal identical to the one we feed into the compressor through the main path, but processed with an equalizer so that only the part of the signal's spectrum we want affects it). We can also use the internal option, where with the bandwidth, frequency and gain controls we can select how, and which part of the signal, we want to affect the compressor's control. Finally, the side-chain lets us set the compressor to work as a de-esser too, but not in the way they are commonly conceived (by creating a band-pass or low-pass filter), but as a complete system that compares the relative difference between the "sss" sound and the full-bandwidth signal. To do this, using the bandwidth, frequency and gain controls, we set the area of the signal's spectrum where we want the de-esser to act, comparing the relative "threshold" with that of the full signal, thus compressing the targeted "sibilance" without having to remove frequencies.
Among the controls, we also find the typical threshold, ratio and gain selectors found on all compressors, accompanied by a useful LED bar that shows when the signal is below the threshold and when and how much compression is being applied. In addition, we have two attack and release selectors that let us determine how much time must pass before the compressor starts acting once the signal has crossed the chosen threshold, and how long it takes to change the gain by 10 dB (note that this is a release "rate," not a release "time," which would be how long it takes for compression to stop acting once the signal is back below the selected threshold). It is also possible to set the compressor to handle these two functions in "Auto." Accompanying these selectors there is also the knee control, which, let's say, is how we want the compressor to act "around" the selected threshold; that is, if we choose a "hard" knee, the compressor will apply full compression once the signal has exceeded the threshold, whereas if we choose a "soft" knee, the compressor applies a small proportion of the compression just before the signal crosses the threshold.
On top of all this, each channel has its own bypass switch so we can choose whether we want it to act or simply let the signal "pass" just as it comes in. There is also a selector for choosing the threshold above which we want the limiter to act, accompanied by a small LED bar that shows how many dB the signal is from being limited and exactly when it is being limited.
Finally, between channels 1 and 2 and channels 3 and 4, there is a switch that lets us link them, so that the first channel acts as master over the second, which applies all the settings we make on the first. It should be noted that when using the de-esser, each channel, even when linked, has its own control over this setting.
G4 - Quad Gate/Ducker/Expander
The G4 is Rane's model with features similar to the C4 but dedicated to dynamics control using noise gates. This unit, in particular, offers three selectable functions on four independent channels: Gate, in which case we can attenuate the input signal by a number of dB, depending on the chosen depth, until it reaches the selected threshold; Ducker, with which we can reduce the level of the input signal according to the chosen depth when a second signal fed into the side-chain input (see the C4's features in this regard) reaches the selected threshold, for example, the way a talkover works on some desks; and Expander, where, by operating the gate in this mode, we can expand the dynamic range of the signal, thus reducing the noise around it.
As for the technical features and operating options the G4 offers, we have:
Connectivity is exactly the same as on the C4: an independent input and output for each channel, with balanced XLR connectors linked to balanced jacks, and four jacks for externally controlling each channel's side-chain.
As for the controls, we also have the option of choosing whether to control the side-chain with an external signal via the corresponding input or with the internal option, although in this case we cannot set the key to a specific frequency band. What we do have here is a high-pass filter and a low-pass filter so that the gate only acts within the chosen band.
Of course, we also have the threshold selector and two very important ones: depth and ratio, in gate and ducker mode. Depth sets how many dB the signal is attenuated once the signal has crossed the threshold. Ratio determines, in expander mode, the rate at which the output signal increases relative to the input. These selectors are accompanied by a useful LED bar that shows when the signal is below the threshold and another that shows when the gate is closed or open. In addition, we have two selectors: attack, which lets us determine how quickly the gate opens or the ducker acts, or, in the case of the expander, what the increased gain ratio is; and release, which indicates how quickly the gate closes, the ducker stops acting or the signal returns to its state after the expander. Next to these two selectors we have hold, which sets how long, after the signal has dropped below the selected threshold, the gate stays open or the ducker keeps acting (this selector has no effect in expander mode).
Like the C4, each channel has its own bypass switch, and between channels 1 and 2 and channels 3 and 4 there is also a link switch.
ANALYSIS
I ran an exhaustive test of the C4, comparing it with a more standard unit, the DBX 160, and a Spanish-made unit with similar features, the Altair CN-220. I also compared the G4 with a standard such as the Drawmer DL-231 and with the Altair NG-440.
In the compressor we find a very useful tool for compressing only the frequency band we want, with very precise adjustment through the side-chain, plus all the options it offers for making our compression of the original signal more precise, with the knee selector being very useful for smoothing out the compression effect. The only thing I would say is that the dynamic range the 160 gives us is somewhat greater, but that does not diminish the quality of this unit.
The gate gives us lots of options for processing the signal, is really easy to use, and has as many possibilities as the C4. I also really like having "depth" on a gate so I can soften its effect.
Both units respond very well to all their controls, giving us the responses we expect when using them.
TECHNICAL SPECIFICATIONS OF THE C4 AND G4
Input impedance is 10 kOhms. Output impedance is 100 Ohms maximum. It has a frequency response of 15 Hz to 20 kHz and a signal-to-noise ratio of 0.02% from 20 Hz to 20 kHz.
CONCLUSIONS
Both the C4 and the G4 are very good and very complete units, although it is true that live you don't have time to fine-tune each signal enough to get the most out of what they offer. It is welcome to have a unit that offers four such complete channels of compression or noise gating in just two rack units, quite similar to others from well-known brands, which, let's say, it matches in sound quality. There is a marked improvement in quality compared to this brand's earlier units, and the finish has improved a lot.
