Test Drive: The Symetrix 601 Digital Voice Processor


by Jerry Vigil

Look around your studio. If you're one of the lucky ones that has a fairly "new" studio, it's loaded with digital gear. You're pulling music beds from CDs. You're producing on a digital workstation. You're mastering digitally to DAT. As analog quickly becomes the exception and digital the norm, one thing remains the same. You still need microphones to record the human voice, and what the microphone converts the sound to is an analog signal. If you're going to be "digital," that microphone needs to get plugged into a box like the Symetrix 601 Digital Voice Processor.

The single rack-space unit flaunts a distinctive front panel consisting of 31 grey buttons, each of which has a small red LED at its center. If you like lots of lights, you'll like the way the 601 lights up when the power is turned on! Why so many buttons? The trend in the past few years has been to make digital processors with only a few controls on the front panel. The result is the need to constantly scroll through various parameters and menus in a display screen until you get to the one you want. The 601 brings a lot of these parameters back to the front panel for quick and easy access. This comes in very handy because the 601 delivers a lot of processing power in one package. You get fully parametric EQ, shelving EQ, notch filtering, dynamic noise filtering or noise reduction, de-essing, delay, stereo synthesis, gating, expansion, compression, and AGC (automatic gain control).

The 601 accepts either a mike or line level analog signal (or both), converts it to 18-bit digital audio, and performs its 24-bit digital processing at a rate of over 50 million instructions per minute (MIPS). The mike and line level analog inputs are both balanced XLR types. The 601 also accepts digital inputs (44.1kHz or 48kHz) in either the AES/EBU or S/PDIF format via XLR jack for AES/EBU and RCA jack for S/PDIF. There are two balanced XLR analog outputs (left and right channel) and two stereo digital outputs, XLR for the AES/EBU format and RCA for the S/PDIF. Rear panel buttons select S/PDIF or AES/EBU. The 601 is a true stereo processor utilizing two digital signal processors or DSPs. The digital inputs are stereo. The analog inputs are mono, but once the analog signal is converted to digital, it is split, and identical signals are sent to each of the two DSPs. Though the 601 has two DSPs, they are not individually accessible. Whatever processing is being applied to one channel is being applied to the other, and adjustments made to a parameter effect both DSPs identically. The delay line is the only exception to this. Phantom power is provided and turned on and off on the rear panel. MIDI input and output jacks facilitate MIDI program change as well as MIDI parameter editing.

The Symetrix 601 provides 128 factory presets and 128 user memory locations. For the radio producer who is recording voice tracks from several different people on a regular basis, the ability to save and recall a variety of settings instantly is a major plus. The first thing on the Test Drive to-do list was to put a voice track on a continuous loop and scroll through all 128 of the presets. Surprisingly, there were a large number of useable "effects" that weren't expected. Most of these utilized the unit's delay section. Though the delay section is simple, it still provides several effects you'd normally go to an "effects box" to get. More on the delay section later. Many digital processors with factory presets provide descriptive "names" for the presets usually shown in a large multi-line LCD display. The 601 doesn't display preset names on its small, 4-character LED display. However, names and descriptions for the 128 factory presets are included in the owners manual.

At the far left of the front panel are two input level controls, one for the mike level input and the other for the line level input. A unique feature of the 601 is its ability to use both analog inputs simultaneously. This, in effect, makes the 601 a mixer of sorts. Red LEDs next to the level controls indicate whether the unit is set to line input, mike input, line/mike inputs (mixer mode), or digital input. A ten-LED bargraph above the level controls displays input headroom and includes a Clip LED to indicate overloading of the analog inputs.