British company SCV, owner of LA Audio, has finally renewed its classic four-channel gate, giving it new features, improving its overall quality (just look at the spec sheet) and, above all, completely rethinking how it is used by reworking and completing its "sidechain." Every year, mid-range sales of mid-to-high-quality products get harder, since the market is flooded with Asian products that, while clearly inferior, work and can fill slots in not-too-demanding racks.
So let's look at where the real reasons for spending a little more lie, other than the proud "Made in UK" on the back panel or bragging to our "buddies" about another unit in our dynamics rack. We will also "take apart" and analyze both the design and construction of this unit, the quality of its components, its resistance to the rough handling of touring and its "life expectancy."
DESCRIPTION
The G400 is a module with four noise gates in a single rack unit. They can work individually or as two stereo pairs, governed by channels one and three, where the "RMS SUMMING" system ensures that both linked gates are controlled by both signals, rather than the classic "link" where channel one's "key" controls channel two.
Each channel has a high-pass filter (from 22 to 3k) and a low-pass filter (from 250 to 30k) to control the signal that opens the gate (not the processed signal), a threshold control, and a range switch for full muting (-80 dBu) or a gentler level of attenuation (-20 dBu). There is also a switch to choose the attack (fast or slow), and the release is adjustable from 0.01 to 4 seconds.
A listen switch lets us hear the sidechain signal that triggers the gate, so we can adjust the high-pass and low-pass filters by ear. This signal can also be external, for which there is a jack input per channel. All inputs and outputs are electronically balanced and can be switched between +4 and +10 dBu.
IN DEPTH
The heart of each G400 noise gate is called the THAT 4301 IC. It is an integrated circuit (a "chip," in plain terms) produced by THAT Corporation and trademarked as "The Analog Engine." It is made up of four sections. The main one is a high-performance, exponentially controlled VCA, responsible for that final 0.05% distortion, since this chip's specs are brutal: a dynamic range of 115 dBu and total distortion of 0.003% at 0 dB gain, while at gain factors up to +10 its dynamic range only drops to 85 dBu.
A VCA is a voltage-controlled amplifier, that is, a device that automatically adjusts its volume depending on a second signal derived from it (which we can shape), called the "sidechain," which we then feed back into the original signal, which changes according to the design and the actual shaping we do in this circuit. We call that signal the "key." Depending on the sidechain design, we get a compressor, a gate, a de-esser...
The second section of our chip is a logarithmic RMS detector, which is combined with the VCA to deliver response accuracy previously unknown in small circuits. Whenever we bought a unit with four dynamics channels instead of a simple stereo unit, the circuits assigned to each channel were always restrained in their design, so we did not get all the corrections that larger circuits provided. This difference showed up as a lack of precision, which became even more evident with four identical units that could be compared with one another.
The chip is completed by two operational amplifiers, which help reduce the size of the final circuit and the overall power consumption.
In the sidechain, the circuitry is based on well-known (effective and low-noise) designs using TI 072 op-amps, perhaps one of the most widely used and the favorite of the British audio industry.
Power is well supplied by a toroidal transformer, each channel's startup is protected by an individual relay, and there is a general internal fuse to prevent damage from voltage fluctuations in the mains.
The potentiometers are Alpha—functional, not high-end, but of proven durability, so we will have noise-free control for many, many years.
The overall quality of the soldering and boards, as well as the components, is very good. No component is surface-mounted and all boards are double-sided fiberglass. All of this gives us confidence for heavy use on the road.
IN OPERATION
The quality of the processed sound is fantastic for a four-channel gate, especially considering the price per gate, and comparable to mid-to-high-end stereo units. Distortion is low and gives a very transparent feel, in some cases as if nothing were inserted at all—a comparison we made with two channels on my Yamaha DM2000, one with the unit inserted and the other with the duplicated signal. This is also where I checked the behavior of the hard-wired input-output "bypass," a more than adequate comparison tool.
In the sidechain we have the threshold control, quite accurate, with two starting positions, -80 and -20, and control from -20 to -50, which allows us to be very precise and achieve almost invisible gating. The attack can be fast or slow, which is enough for a four-channel gate module. In addition, we have to be very careful with the release, since otherwise there is a certain tendency toward "triggering," or pumping. This may be the biggest flaw we found, but on the other hand we get long release times for processing non-percussive sounds and making good use of tom tails.
The great advantage of this unit lies in its filters for the sidechain signal, the signal we process to open or close the gate. These filters allow us, for example, to separate a tom from the rest of the kit, so that the kick or snare don't open the gate with their sound, since we can perfectly isolate the tom's own frequency and make it the only one in charge of the processor.
These filters also give us extra protection against low-frequency feedback live, since we can use the high-pass filter so that our "key" signal doesn't open the gate due to the low-end buildup our P.A. can produce. That way we don't have to "neuter" the low end of the processed signal, combining clarity and punch.
Each gate also has two LEDs for open/closed and another to indicate an external "key" signal insert.
CONCLUSIONS
The overall impression is one of a big improvement in quality over the previous model. More durability, very good behavior, a new creative dimension thanks to its sidechain filters, and a good finish... All of this makes it a good time to complete your rack with a four-channel gate, which you are surely missing these days...
