Hands-On Review:dbx 231 EQ and 166XL Comp/Limiter

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Pure, natural signal integrity and fabulous flexibility made affordable

By Norman Castle


dbx 231 EQ and 166XL Comp/Limiter

Featuring incredibly low price tags, dbx’s analog signal processors deliver the transparency, instant response, and untrammeled transients that impart the totally natural feel associated with vintage analog stage and studio gear. dbx’s analog mic preamps, limiters, crossovers, dedicated gates, and patchbays are manufactured with the benefit of dbx’s extensive engineering experience and expertise for a performance/dollar ratio the competition can’t touch. And dbx pretty much defined modern compression and EQ. Hence, it’s no surprise that the analog 166XL Compressor/Limiter/Gate and the 231 Dual Channel 31-Band Graphic EQ performed above and beyond the call of duty.


Why analog?


In the beginning, all gear was analog gear, which became very good at retaining all the subtle, indefinable sounds and transients that really bring music to life. When digital came along, the big challenge was the analog/digital and digital/analog converters, which often slowed down signal response and lost information—just enough to alert the unconscious mind that something was not quite right. So, after a volatile romance with digital, many engineers went back to the tried and true analog stuff.

Since then, digital sound quality has steadily climbed to the point where the good stuff can fool even golden ears. Unfortunately, the good stuff is also the expensive stuff. That’s where dbx’s analog processors come in. To achieve similar signal integrity and sound in the digital realm, you’ve usually got to lay out a lot of bread. dbx’s analog gear gives you sound and flexibility a professional can be happy with for prices real musicians can handle.



dbx 166XL Dual Compressor Limiter & dbx 231 Dual 31-Band Graphic EQ

dbx 166XL Dual Compressor Limiter & dbx 231 Dual 31-Band Graphic EQ

166XL—the cat herder


If you’ve been playing out for a while or if you’ve worked with multiple musicians in the studio, you’ve already discovered that keeping everybody’s sounds in the same dynamic universe can be like herding cats. The dbx 166XL Compressor/Limiter/Gate can take care of all your signal excesses in one fell swoop. The coolest feature of this unit is its automated attack and release function.


Just activate the auto mode and the 166XL’s attack and release time parameters release automatically and continuously adjust to the music. You still control the ratio, threshold, and output levels but the attack and release sound totally organic without your intervention. Both while recording and on a live gig with my four-piece, this function produced better results than I could achieve adjusting the attack and release manually. I could hear no telltales that the 166XL was in the chain; it just sounded like all the levels were closer together, the bass was not booming out of control, the guitars had much fuller sustain, and the quieter passages didn’t get lost in the sauce.


In the studio, I used the sidechain function to contain a very spiky bass drum. I ran the signal through the sidechain into my graphic EQ, where I boosted the bass drum frequencies and cut everything else. The bass drum was drawn back into line without compressing the rest of the signal. Very cool.


Big LEDs for gain reduction, compression threshold, and gate threshold make the 166XL a piece of cake to set up. And the gate seems to have an uncanny ability to distinguish transients, decay tails, and reverb tails from noise. It keeps things quiet but never at the cost of the music. The gate release algorithm smooths out release characteristics so that you don’t get the sudden background level jumps and dropouts that can plague cheaper gates.


You can run the 166XL linked in stereo or as two separate units. Running separately can be very handy in live situations where you can give the drums separate compression from the rest of the band. Put the 166XL just before your crossover and set the limiter to just below clip level to protect your PA. Use compression to bring all the levels up toward the amp’s upper operating range and you can get a lot more volume out of your power amps without overloading them.


231 EQ—mighty mite


The strengths of the 231 Dual Channel 31-Band Graphic EQ are right out front. Namely, it’s a full-featured EQ good enough for pro applications that fits in two measly rack spaces and costs less than the bail to get your drummer out of jail. Switchable boost/cut ranges of ±6dB or ±12dB give you precision control over the 31 - 1/3-octave constant Q frequency bands with smooth and silent 20mm nonconductive nylon faders.


Four-segment LED ladders monitor the output while a 12dB per octave 40Hz low-cut filter removes stage rumble freeing up headroom in your amp without brutally chopping off your bottom end. With a huge dynamic range of over 108dB and frequency response of 10Hz to 50kHz, it can handle any gig and it won’t break the bank. The 231 is the perfect FOH or monitor EQ for weekend warriors and touring bands.


Together, the dbx 166XL Compressor/Limiter/Gate and dbx 231 Graphic EQ make a killer signal processing combo for live or studio use. They provide very powerful sound command without commanding a very powerful bank account.



Features & Specs:


dbx 166XL Compressor/Limiter/Gate:

  • Classic dbx auto mode
  • Innovative gate timing algorithms for smooth release
  • V1 VCA for extra-wide threshold range
  • Program-adaptive expander/gates
  • Stereo or dual-mode operation
  • Balanced I/O with 1/4" TRS and XLR jacks
  • Sidechain insert
  • True RMS power summing for solid stereo image
  • Hard knee or overeasy compression algorithms
  • PeakStop limiter
  • Artifact-free performance


dbx 231 Dual Channel 31-Band Graphic EQ:

  • 2 - 31-band, 1/3-octave Constant Q frequency bands
  • Switchable boost/cut ranges of ±6 or ±12dB
  • 12dB per octave 40Hz low-cut filter
  • Front-panel bypass switch
  • ±12dB input gain range
  • 4-segment LED ladders for output-level monitoring
  • XLR and TRS inputs and outputs
  • Internal toroidal transformer
  • <10Hz to >50kHz frequency response
  • >108dB dynamic range