dbx 160X

Name: dbx 160X
Brand: dbx

A single-channel compressor with stereo linking, a lit meter and a knob that can turn the dynamics upside down.

Overview

The 160X is dbx's answer to its own bestseller. Period advertising called the Model 160 one of the world's best-selling compressors, but users kept asking for four things: stereo linking, easier rack-mounting, clearer metering, and selectable compression characteristics (Recording Engineer, August 1985, p.51). The 160X is that wish list in a single rack space. It is a professional single-channel compressor/limiter that combines dbx's Over Easy compression curve with a switchable hard-knee mode. The selectable compression is the main idea of the whole unit.

In Over Easy mode, the unit starts to bring in its gain-change circuitry gradually as the signal approaches the threshold. There is no distinct point where processing begins. The threshold setting corresponds to a point midway between the onset of processing and the point where the transfer curve matches the ratio setting. Switch to hard-knee and the threshold becomes a precise reference: signals below it pass through untouched, and signals above it get processed exactly as the ratio control dictates. Most compressors have one curve, and that's that. The 160X gives you a front-panel button to change it.

The engine underneath is the part collectors bring up first. A true-RMS level detector, a wide-range Blackmer voltage-controlled amplifier, and feedforward circuitry let the unit apply large amounts of compression without the audible artifacts that plague lesser designs. Program-dependent attack and release times handle the timing automatically — attack runs 15 ms for a 10 dB input increase above threshold, tightening to 5 ms at 20 dB and 3 ms at 30 dB, while release varies automatically from 0 to 500 ms depending on front-panel settings. The result is natural-sounding gain control without constant fiddling, which is exactly what a tracking or live engineer wants at 2 a.m.

Then there is Infinity+, the feature that has kept the 160X on effects racks long after cleaner digital options arrived. Rotate the compression ratio past the infinity:1 setting and the unit enters negative compression, up to a maximum of -1:1 — a 1 dB decrease in input level above threshold produces a 1 dB increase in output. The program dynamics invert. On a picked guitar, a harpsichord, or a drum, a low threshold will all but eliminate the attack transient; on bowed strings or wind instruments, the level builds normally to threshold and then drops as the instrument plays its loudest, sometimes ending up quieter than the note's onset. It is a special effect, and the manual treats it as one, but it is a special effect no plug-in quite replicates.

Stereo work is handled by strapping. A simple patch cable between the TRS strapping jacks of two 160Xs lets the RMS detectors communicate, but only when one unit's SLAVE button is depressed. Both channels then receive the same amount of compression - the maximum needed by either channel at that moment - so a loud transient on the left doesn't shove the phantom center image sideways. Only the master unit's controls need adjusting. The coupling disengages instantly via a front-panel pushbutton.

Metering is thorough for a single-rackspace unit. The upper row of 19 LEDs displays input or output level from -40 to +20 dB, selectable via the DISPLAY switch and factory-calibrated so 0 dB equals +4 dBm (1.23 V rms) at either input or output. A rear-panel METER CALIBRATION trimmer lets you reset that zero point anywhere from -15 dBm to +10 dBm. The lower row of 12 LEDs shows gain reduction from -1 to -40 dB. Fixed gain changes from the OUTPUT GAIN control are deliberately left out of the gain-reduction display, but they do show up in the output level display. Three threshold LEDs (green BELOW, amber Over Easy region, red ABOVE) round out the front panel.

The I/O is professional-grade and flexible. Signal input impedance is 50 kΩ unbalanced or 100 kΩ balanced. Detector input is 230 kΩ unbalanced or 460 kΩ balanced. Maximum input level is +24 dBm, and the output stage is 22 Ω, designed to drive 600 Ω or greater, with +24 dBm output capability into that load. Connectors are TRS phone jacks and barrier terminal strips, and the inputs are balanced active. The single-ended output can be field-modified for transformer or active balanced operation, and the manual points owners to Jensen Transformers for an isolated floating output transformer. Separate detector inputs mean the sidechain can be fed a different signal than the program. That allows ducking and de-essing tricks that most compressors of the era couldn't do.

The numbers are solid rather than spectacular. Dynamic range exceeds 113 dB. Equivalent input noise is below -89 dBm unweighted across 20 Hz to 20 kHz, and frequency response is +0, -1 dB over the same band. Slew rate exceeds 10 V/µs. Distortion stays low in both regimes. Below threshold, second and third harmonic each measure 0.07% at 1 kHz and 0 dBm. Above threshold at infinite compression, second harmonic holds at 0.07% while third harmonic drops to 0.02%. Maximum compression exceeds 60 dB. Output gain is adjustable ±20 dB and does not interact with the threshold setting. Fixed gain and gain reduction are additive and independent.

Physically, the 160X is a single-rackspace unit at 1-3/4" H x 19" W x 9-1/4" D, weighing 6.5 lbs. Power requirements are 115/220 VAC ±10%, 50-60 Hz, drawing just 8 W. The AB-1 active balanced output card is the listed accessory. A true hard-wired bypass switch takes the unit fully out of the signal path. It is not a relay and not a soft bypass, but an actual hard-wire bypass.

The 160X is not simply a 160 with a new faceplate. The manual itself notes that in hard-knee mode, the 160X performs in the manner of its predecessor, the 160. Everything else - Over Easy switching, Infinity+, stereo strapping, the LED metering - is new.

One practical warning from the manual: placement in the chain matters. The compressor should sit as close to the amplifiers as possible. Put the 160X before an EQ and a boost downstream won't be seen by the unit, which means the speakers take the hit instead. For large sound-reinforcement rigs, the recommended approach is a separate 160X on each output of the electronic crossover, with strapping cables run between pairs in each band - low-low, mid-mid, and so on.