Jan 1, 1999 12:00 PM, Mark Frink


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Released at the last Winter NAMM show, the Symetrix 562E Windowing Expander/ Gate is a full-featured 2-channel gate or downward expander. In addition to all the usual controls and adjustments, a feature called Window Advance allows the entire leading edge of transient signals to pass through the 562E cleanly. Thus, the full impact of a drum's attack is allowed through at even the fastest settings, without clicking or popping.

The 562E under review spent last summer in my FOH effects rack, along with a couple of popular gates by other manufacturers. I used the 562E for drum inputs on many live shows, mostly on kick, and the drums' attack sounded so natural that on several occasions visiting engineers doubted that the gate was working at all. Only by reducing the gate's range to zero and opening it up while they listened on headphones could I convince them that it was, however transparently, gating their kick drum. The Windowing Expander/ Gate provides the full impact of the drum's leading edge, and it may be the best tool for cleaning up the kick for live sound that I've heard.

To recap, a gate on a drum input will automatically shut it off when signal falls below an adjustable threshold. This both eliminates the off-axis sounds of adjacent drums and allows the live engineer to turn the drum channel up louder than would normally be possible without feedback. Obviously, there are other applications in live sound, such as turning off noisy inputs and taking room ambience out of vocal mics, and there are a host of uses for gates in the recording studio.

The Window Advance is a four-stage, all-pass filter that delays the signal through the gate just long enough (about 20 microseconds) for the detector to open before the signal has started passing through the VCA. The gate's envelope is able to track the attack of fast-rising percussive transients by anticipating them, thereby eliminating the "click" that occurs when the waveform is "chopped" on fast attack settings. The Advance switch has two settings, marked Min and Max, and my trials on drum kits revealed that the Max setting should be used to open the gate as quickly as possible. This setting adds a bit of phase shift at higher frequencies, but this is by far preferable to missing the transient on the percussive sounds.

Front panel controls include a knob that, at full counterclockwise, offers 80 dB of gating. Turned clockwise, the control provides downward expansion at a ratio of up to 1:3. When the signal falls lower than 25 dB below the threshold, the expander ratio reverts to 1:1 in order to prevent low-level breathing. Similar in concept to compression, downward expansion scales the signal back by a ratio rather than just shutting it off, and it is better suited than straight gating for noise reduction tasks requiring subtle control.

The Threshold control is accompanied by a green and a yellow LED that shows when the signal is below or above threshold. A vertical row of four red LEDs displays gain reduction of 3, 12, 30 and 60 dB. Other front panel controls adjust attack, hold and release times with a generous range of settings. The fastest attack time setting (fully counterclockwise) is labeled Auto and is meant to be used with the Window Advance setting; it ensures that the gate opens enough before the signal needs to be turned on so that it doesn't click.

In order to tune the gate's detector to ignore unwanted sounds that could trigger it inadvertently, a lowpass filter sweeps up to 1k and a highpass filter sweeps down to 400 Hz. The EQ filters are 12 dB per octave, providing minimal phase delay that the Windowing feature keeps up with easily.

Rear chassis connections include XLR and 11/44-inch TRS jacks for balanced and unbalanced connections. Each channel also has a TRS insert jack for the key signal (tip wired return, ring wired send). The key input may also be used to trigger the gate from an external source. A three-way switch on each channel sends the filtered or unfiltered key signal to the channel's output so that the key signal can be monitored.

Symetrix's new gate easily meets the high level of engineering standards set by the company's other recent analog and digital products. At a list price of only $579, the 562E offers performance not available in gates costing much more.

Symetrix Inc. 14926 35th Ave. W., Lynwood, WA 98037. Phone 425/ 787-3222; fax 425/787-3211. Web site:

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