Test Drive: Symetrix 628 Digital Voice Processor

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Next in line is the de-esser.  Press the ACTIVE button to engage the de-esser.  A green LED lights to indicate it’s in line.  (The de-esser, expander/gate, compressor, and EQ sections all have independent ACTIVE buttons and green ACTIVE LEDs.)  There are adjustments on the de-esser for FREQUENCY and THRESHOLD.  These knobs, like all the knobs on the 628 (with the exception of the GAIN control), rotate infinitely and activate the 3-digit LCD Master display at the far right where parameter values are displayed.  In other words, there isn’t an arrow on the knob pointing to parameter values printed on the panel around the knob.  The result is, you cannot glance at a knob and see where it’s set.  To view a parameter’s setting, turn that knob left or right one click.  This displays the current value.  Further clicks in either direction will change the parameter setting.  The de-esser’s THRESHOLD control sets the level at which de-essing occurs (from -60 to 0dB) and the FREQUENCY control sets the frequency that will be affected (.8 to 12kHz in 100Hz steps).  A dedicated 6-segment LED meter indicates the amount of de-essing/gain reduction occurring.

Next is the Expander/Gate section, again with an ACTIVE button and dedicated six-segment LED gain reduction meter.  There are three controls on the expander/gate.  The THRESHOLD is adjustable from -60dB to -20dB in 1dB steps.  The RATIO is adjustable from 1:1 to 9.99:1 in gradually or logarithmically increasing steps, and the RELEASE time is adjustable from .25 to 5 seconds in 50ms steps.  The Ratio and Release controls were not on the earlier 528 and enable using this section as a fast acting noise gate as well as a downward expander.

At the center of the front panel are the Compressor controls.  This section also has its own 6-segment LED gain reduction meter.  The THRESHOLD is adjustable from -60 to 0dB in 1dB steps, the RATIO is adjustable from 1:1 to 14.8:1 in gradually increasing steps, and the RELEASE time is adjustable from .25 to 5 seconds in 50ms steps.

The Parametric EQ section offers three bands with controls for FREQUENCY, BANDWIDTH, and CUT/BOOST.  A button toggles between the three bands, and the selected band is indicated with a red LED for LOW, MID, and HIGH.  The low band frequency is adjustable from 20 to 500Hz in gradually increasing 1Hz to 10Hz steps.  The bandwidth is adjustable from .3 to 4 octaves in increasing steps from 1/100 octave to 1/10th octave, and cut/boost is -15 to +15 in 1dB steps.  Bandwidth and cut/boost parameters are the same for all three bands.  The middle band frequency is adjustable from 160Hz to 6300Hz in 10Hz steps below 1K and 100Hz above 1K.  The high band frequency is adjustable from 680Hz to 20kHz in 10Hz steps below 1K and 100Hz steps above 1K.  (The high band tops out at 16kHz when 32kHz sampling is set on the rear panel.)  Because the bands are overlapping, it is possible to boost/cut up to 30dB on a very wide range of frequencies!

The Master section at the far right offers an OUTPUT LEVEL knob (+/-15dB) and an 8-segment headroom meter with a clip LED.  The large 3-digit LED display is easy to read from a distance.  The PRESET control scrolls through the 127 presets.  The 128th (or preset #0) is a bypass mode which can be copied and saved to other locations to “reset” them to zero processing.  To load a preset, dial it up and press the LOAD button.  If adjustments are made to the preset, the LED flashes to indicate it has been edited.  To store it, turn the PRESET control to the desired location then press the SAVE button.  The display will read “Sto,” and a second press of the SAVE button actually stores the preset.  The unit is shipped with eight “ready to go” presets at locations 120-127.  These are read only and provide good starting points for various applications.

We tested the 628 on both a Neumann U87 and a Shure SM5B.  Because of the 628’s digital nature, setting up levels was an important first step, and the result was a great sound from a very quiet box.  The pre-amp is transformerless, has no capacitors, and incorporates filters to reduce RF interference.  The compressor performed wonderfully, keeping the signal clean even at large amounts of gain reduction.  The fact that there are only three parameters for both the compressor and the expander/gate make them both easy and fast to set up.  The de-esser was equally easy to use.  With a digital readout of parameter values, it is simple to zero in on offending frequencies to de-ess by going to the EQ first, setting the boost to about 10dB, then scrolling the frequencies until the target frequency jumps out at you.  Then, reset the EQ, go to the de-esser, dial in that frequency, and adjust the threshold to set the amount of de-essing. 

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