COMPRESSOR LIMITER / GATE

dBu +20

PEAKSTOP LIMITER

OUTPUT GAIN

Most compressor/gates provide less than musical compression, coupled with gating that swallows transientsor closes early, cutting off decay and reverb tails. The superb engineering in the 166XL ensures that both its compression and gating provide versatility and excellent sonic performance in situations where other compressor/gates typically produce undesirable processing artifacts. When using the 166XLs Attack and Release controls, artists and engineers will find that the center settings deliver classic dbx compression, while the full control range produces voicings that extend from slow leveling to aggressive peak limiting. The 166XLs advanced gate circuitry uses a completely new, program-dependent timing algorithm to produce ultrasmooth release characteristicseven with complex signals, such as voice or reverb decays. dbx engineers went on to take advantage of the wide dynamic range and high precision of the dbx V2 VCA to design in an extra-wide threshold range and ensure top gating performance for each application. Separate precision LED displays for gain reduction, compression threshold and gate threshold allow quick, accurate setup, while the 166XLs intuitive operation lets users easily smooth uneven levels, add sustain to guitars, squash drums or tighten up mixes. In Stereo couple mode, the Channel 1 controls become Master controls, and Channel 2 follows precisely to ensure a rock solid stereo imageeven with high amounts of compression, through True RMS Power Summing. Professionals and newcomers alike will find that the 166XL sets up rapidly and musically the first time it is used, especially with the Auto attack and release function. Advanced applications are now easy, with the 166XLs full sidechain functionality, and the ability to use either hard knee or OverEasy compression algorithms. Add to this already impressive list of features the venerable PeakStop limiter, and youve got a strong finisher, every time. Designed and manufactured in the USA, the dbx 166XL processor is the result of an intensive engineering and product development effort aimed at taking advantage of the latest and best advances in manufacturing technology to deliver true dbx audio performance and reliability to our customers at the lowest possible cost. The 166XL puts a completely new level of compressor/gate performance within everyones reach.

Bypass

dB +20

GAIN REDUCTION (dB)

4:1 :1 1.3:1 0

Fast Fast 2:1 Slow

OverEasy

1:1 -30

CHANNEL TWO

Contour

OFF dBu +15 dBu +20

-40 -45

BELOW ABOVE

Stereo Couple Bypass

2 -10 Slow 4 -20

Slow Fast

ATTACK COMPRESSOR

RELEASE

MASTER
THRESHOLD RELEASE EXPANDER/GATE

SC Enable

THRESHOLD
Goof proof operation to smooth uneven levels, add sustain to guitars, fatten drums or tighten up mixes. New gate timing algorithms ensure the smoothest release characteristics. Program-adaptive expander/gates. Great sounding dynamics control for any type of program material Separate precision LED displays for gain reduction, compression threshold and gate threshold allow quick, accurate setup.

CHANNEL ONE

Stereo or dual-mono operation. Balanced inputs and outputs on 1/4" TRS and XLR. Side Chain insert. Classic dbx Auto mode.

1:1 Slow Fast -40

8760 S. Sandy Pkwy. Sandy, Utah 84070 Phone (801) 568-7660 Fax (801) 568-7662 Intl Fax (219) 462-4596 customer@dbxpro.com http://www.dbxpro.com

OFF dBu +15

-25 -45
A Harman International Company
COMPRESSOR / LIMITER / GATE
GAIN REDUCTION (dB) BELOW ABOVE BELOW ABOVE
-10 -20 -45 -10 -30 +1.3:1 2:1 4:1 -+10 +5
GAIN REDUCTION (dB) ABOVE

+10 +15 -45

-10 2:+10 1.3:1 4:1

-10 +10 +5

+10 +15

-25 -25 -10

Fast Slow -40

1:1 :1 Fast Slow

Fast Slow -20

Stereo Couple

Fast Slow

15 WATTS

MANUFACTURED UNDER ONE OR MORE OF THE FOLLOWING U.S. PATENTS 3,681,618 3,714,462 4,097,767 4,329,598, 4,403,199 4,409,500 4,425,551 4,473,793

CHANNEL 1 INPUT

PROFESSIONAL PRODUCTS A HARMAN INTERNATIONAL COMPANY SALT LAKE CITY, UTAH MADE IN USA MODEL 166A XL COMPRESSOR/LIMITER/GATE

OUTPUT

SIDECHAIN INSERT

CHANNEL 1 INPUT OUTPUT

PHONE: TIP
SIDECHAIN RING INSERT SLEEVE

XLR: PIN 1 PIN 2 PIN 3

100V 50/60Hz 120V 60Hz
The compressor/limiter/gate shall have two idenInputs (1/4 TRS Phone and XLR) Floating Balanced; XLR: Pin 2 and TIP HI, Impedance >50k balanced, >25k unbalanced Maximum Level +24dBu, Balanced or Unbalanced tical channels, each with an audio frequency CMRR >40dB at 1kHz, typically >55dB response of 5Hz-40kHz, +0, -0.5dB, a balanced Sidechain Insert (1/4 TRS Phone)Normalled: Ring = Output (send); Tip = Input (return) input impedance of not less than 40k, with a Impedance Tip = >10k (Input) Ring = 2k (Output) maximum input level of not less than +21dBu and Maximum Level +24dBu Outputs (1/4 TRS Phone and XLR)Floating Balanced; XLR: Pin 2 and TIP HI a 1/4" TRS input connector. The output impedImpedance 120 balanced, 60 unbalanced Maximum Level +21dBu,>+20 dBm into 600, balanced or ance shall be no more than 50 unbalanced, 100 unbalanced Frequency Response 20Hz - 20kHz; +0, -0.5dB,Typical 3dB points balanced with a maximum output level of not less are 0.35Hz and 110kHz, unity gain Noise <-90dBu, 22Hz to 22kHz, no weighting, unity gain than +20dBu, a minimum load impedance at not THD+ N Typically <0.04%; Any Amount of Compression Up to 40dB@1kHz more than 600 and the connector type shall be SMPTE IMD Typically <0.08% @ +10dBu (15dB Gain reduction) 1/4" TRS. Total Harmonic Distortion shall be less Compressor Threshold Range -40dBu to +20dBu than 0.2% with any amount of compression at Threshold Characteristic Selectable OverEasy or Hard Knee Compression Ratio Variable; 1:1 to Infinity:1; 60dB Maximum 1kHz, and Intermodulation Distortion shall be less Compression Attack Time Variable program-dependent; 3ms to 340ms than 0.2%. The unit shall have an output noise for 15dB gain reduction Release Rate Variable program-dependent; 200dB/Sec to level of not more than -93dBu unweighted, and a 3dB/Sec dynamic range not less than 114dB. Outputs shall be gain adjustable in the amount of 20dB from nominal gain via front-panel Output Gain controls, and all outputs shall be capable of driving a short circuit indefinitely with maximum input applied. The compressor attack and release times shall be scalable and program dependent. The gate attack time shall be <100sec. The compression threshold shall range from -40 to +20dB. The gate threshold range shall be from -60 to +10dBu. The compressor/gate shall have a stereo coupling switch as well as the following controls for each channel: Compressor Threshold, Compressor Ratio, Attack, Release, Auto switch Output, Gain, Expander/Gate Threshold, Expander/Gate Ratio, Bypass. The following metering LEDs shall exist for each channel: Compressor Threshold (Below, At Above), Gain Reduction and Gate Threshold (Above and Below). The unit shall operate from a power source of 100 VAC 50/60 Hz to 120 VAC 60 Hz for a domestic unit and 230 VAC 50 Hz for a european unit via IEC type AC cable and shall consume no more than 15 W. The net weight shall be 7lbs. (3.2kg). The unit shall be a dbx 166XL Compressor/Gate. dbx engineers are constantly working to improve the quality of our products. Specifications are, therefore subject to change without notice.

Expander/Gate Threshold Range Expansion Ratio Maximum Depth Attack Time Release Time PeakStop Limiter Threshold Range Gain Adjustment Range Interchannel Crosstalk Dynamic Range Stereo Coupling Operating Voltage Power Consumption Operating Temperature Dimensions (H x W x D) Rack Space Weight
OFF to +15dBu 10:1 >60dB <500s (from Maximum Depth) Adjustable, 30ms to 3sec (to 30dB attenuation) 0dBu to +20dBu Variable; -20dB to +20dB <-80dB, 20Hz to 20kHz >115 dB True RMS Power Summing 100 VAC 50/60Hz; 120VAC 60Hz 230 VAC 50/60 Hz 15 Watts Maximum 0C to 45C (32F to 113F) 1.75" x 19" x 6.75" (4.45 cm x 48.2 cm x 17.15 cm) 1 Rack Unit (1U High) Net weight: 5.05 lb (2.29 kg) Shipping weight: 7.20 lb (3.27 kg)

0dBu =0.775Vrms.

Specifications are subject to change.
FOR MORE INFORMATION CONTACT: dbx Professional Products 8760 S. Sandy Pkwy. Sandy, Utah 84070 Phone (801) 568-7660 Fax (801) 568-7662 Intl Fax (219) 462-4596 customer@dbxpro.com http://www.dbxpro.com

MODEL 166XL

COMPRESSOR G AT E
A Harman International Company

WARNING

CAUTION
RISK OF ELECTRIC SHOCK DO NOT OPEN
FOR YOUR PROTECTION, PLEASE READ THE FOLLOWING:
WATER AND MOISTURE: Appliance should not be used near water (e.g. near a bathtub, washbowl, kitchen sink, laundry tub, in a wet basement, or near a swimming pool, etc). Care should be taken so that objects do not fall and liquids are not spilled into the enclosure through openings. POWER SOURCES: The appliance should be connected to a power supply only of the type described in the operating instructions or as marked on the appliance. GROUNDING OR POLARIZATION: Precautions should be taken so that the grounding or polarization means of an appliance is not defeated. POWER CORD PROTECTION: Power supply cords should be routed so that they are not likely to be walked on or pinched by items placed upon or against them, paying particular attention to cords at plugs, convenience receptacles, and the point where they exit from the appliance. SERVICING: To reduce the risk of fire or electric shock, the user should not attempt to service the appliance beyond that described in the operating instructions. All other servicing should be referred to qualified service personnel. FOR UNITS EQUIPPED WITH EXTERNALLY ACCESSIBLE FUSE RECEPTACLE: Replace fuse with same type and rating only. MULTIPLE-INPUT VOLTAGE: This equipment may require the use of a different line cord, attachment plug, or both, depending on the available power source at installation. Connect this equipment only to the power source indicated on the equipment rear panel. To reduce the risk of fire or electric shock, refer servicing to qualified service personnel or equivalent.
A T T E N T I O N : RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR W A R N I N G : TO REDUCE THE RISK OF FIRE OR ELECTRIC
SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE The symbols shown above are internationally accepted symbols that warn of potential hazards with electrical products. The lightning flash with arrowpoint in an equilateral triangle means that there are dangerous voltages present within the unit. The exclamation point in an equilateral triangle indicates that it is necessary for the user to refer to the owners manual. These symbols warn that there are no user serviceable parts inside the unit. Do not open the unit. Do not attempt to service the unit yourself. Refer all servicing to qualified personnel. Opening the chassis for any reason will void the manufacturers warranty. Do not get the unit wet. If liquid is spilled on the unit, shut it off immediately and take it to a dealer for service. Disconnect the unit during storms to prevent damage.

U.K. MAINS PLUG WARNING

A moulded mains plug that has been cut off from the cord is unsafe. Discard the mains plug at a suitable disposal facility. NEVER UNDER ANY CIRCUMSTANCES SHOULD YOU INSERT A DAMAGED OR CUT MAINS PLUG INTO A 13 AMP POWER SOCKET. Do not use the mains plug without the fuse cover in place. Replacement fuse covers can be obtained from your local retailer. Replacement fuses are 13 amps and MUST be ASTA approved to BS1362.
ELECTROMAGNETIC COMPATIBILITY
This unit conforms to the Product Specifications noted on the Declaration of Conformity. Operation is subject to the following two conditions: this device may not cause harmful interference, and this device must accept any interference received, including interference that may cause undesired operation. Operation of this unit within significant electromagnetic fields should be avoided. use only shielded interconnecting cables.

SAFETY INSTRUCTIONS

NOTICE FOR CUSTOMERS IF YOUR UNIT IS EQUIPPED WITH A POWER CORD. WARNING: THIS APPLIANCE MUST BE EARTHED. The cores in the mains lead are coloured in accordance with the following code:
DECLARATION OF CONFORMITY
Manufacturers Name: Manufacturers Address: declares that the product: dbx Professional Products 8760 S. Sandy Parkway Sandy, Utah 84070, USA

GREEN and YELLOW - Earth

INSPECTION

Verify that the 166XL package contains the following: 166XL Unit AC Power Cord Operation Manual Registration Card

OPERATING CONTROLS

Front Panel
GAIN REDUCTION (dB) BELOW ABOVE BELOW ABOVE
-10 -20 -45 -10 -30 +1.3:1 2:1 4:1 -+10 +5

+10 +15 -45

CHANNEL ONE

SC Enable

OFF dBu +15

Contour

Fast Slow -40

dBu +20

OverEasy

1:1 :1 Fast Slow

Fast Slow -20

dB +20

Bypass
Stereo Couple PEAKSTOP LIMITER

MASTER

THRESHOLD RELEASE EXPANDER/GATE

THRESHOLD

ATTACK COMPRESSOR

RELEASE

OUTPUT GAIN

EXPANDER/GATE Section

Expander/Gate THRESHOLD Control and LEDs (BELOW/ABOVE): Adjusting this control sets the level at which the gate will open and allow the signal at the input to pass through to the output. Turning the knob fully counterclockwise (to OFF) allows the gate to pass signals unattenuated, effectively bypassing the gate. Turning the knob fully clockwise causes the gate to attenuate input signals below +15dBu. The two Expander/Gate LEDs indicate the relationship of the input signal level to the threshold setting. The red LED lights when the signal is BELOW threshold, the green LED lights when the signal is ABOVE threshold.
Note: The 166XLs expander/gate attack rate (which controls how fast the signal is restored after being attenuated) is internally set to be very fast - fast enough to allow all of the transient at the beginning of a note, vocal or spoken word to come through.
Note: The 166XLs expansion ratio is internally fixed, at approximately 10:1. This ratio helps to eliminate the artifacts normally associated with common switch gates. Attenuation is >50dB.
SIDECHAIN (SC) ENABLE Switch and LED: This switch enables the 1/4 TRS connector of the sidechain, allowing external processing of the detector signal. It has no effect if there is nothing plugged into the sidechain loop; however the switch will still light indicating the sidechain is enabled. Expander/Gate RELEASE Control: This control determines the rate at which the gate closes once the signal at the INPUT or SIDECHAIN INSERT falls below the threshold. SLOW settings are useful for gating out noise present behind vocals and acoustic instruments. FAST settings are useful for tightening up the sound of percussion (e.g., kick or snare drum) and drying up leakage from other instruments into percussion tracks.

LIMITER Section

PEAKSTOP LEVEL Control and LED: This control allows you to set the maximum peak output level of the 166XL regardless of any other control. PeakStop comes after the compression, gating and output gain circuitry; this provides for an absolute limit to be put on the peak excursions at the output. PeakStop works instantaneously; you can apply moderate amounts of dbxs OverEasy compression and still be protected from large transients, other short-term overloads and overmodulation. PeakStop is a smooth well-controlled soft clipper whose behavior is sonically similar to the gentleness of OverEasy compression; its clipping is much preferable to a power amps or analog-to-digital converters. PeakStop rounds the corners of a peak rather than cutting it off sharply. By making a signals leading and trailing edges curved instead of sharply angled, it reduces the amount of higher odd-order, offensive-sounding harmonics that conventional hard clipping causes. The level at which PEAKSTOP is activated is adjustable from +0dBu to +20dBu. Note that small signal excursions above the set value of PEAKSTOP are possible, to allow the rounding to occur. Therefore, for applications where you must not exceed a given ceiling, set the PEAKSTOP control 1dB to 2dB below the ceiling. The PEAKSTOP LED illuminates whenever peaks attempt to exceed PeakStop level and are reduced in amplitude. If the PeakStop LED illuminates when the PEAKSTOP LEVEL control is set to +20dBu, the headroom capabilities of the 166XL are being exceeded and hard clipping is occurring.

MASTER Section

STEREO COUPLE Button and LED: This button toggles the unit between stereo and dual mono operation. Press the STEREO COUPLE button In for stereo operation where Channel 1 becomes the master controller for both channels. All of Channel 2s controls, buttons, and LEDs will be disabled (except for Channel 2s BYPASS, SIDECHAIN ENABLE, and CONTOUR buttons, and its GAIN REDUCTION LEDs), since Channel 2 is the slave. Note that the detection circuitry senses the true RMS levels of the combined signal, so it is unaffected by phase shifts (or other discrepancies) between the channels. This ensures stereo compression without loss of imaging stability. With the STEREO COUPLE button Out, the unit functions as two separate mono compressor/gates, each with its own independent controls. The STEREO COUPLE LED indicates that the 166XL is stereo-coupled. Rear Panel

15 WATTS

100V 50/60Hz 120V 60Hz
PROFESSIONAL PRODUCTS A HARMAN INTERNATIONAL COMPANY SALT LAKE CITY, UTAH MADE IN USA MODEL 166XL COMPRESSOR/LIMITER/GATE
PHONE: TIP RING SLEEVE XLR: PIN 1 PIN 2 PIN 3
MANUFACTURED UNDER ONE OR MORE OF THE FOLLOWING U.S. PATENTS 4,234,804 4,316,107 4,329,598 4,331,931 4,377,792 4,403,199 4,409,500 4,425,551 4,434,380 4,454,433 4,471,324 4,473,793 OTHER PATENTS PENDING

CHANNEL 2

OUTPUTS +4 dBu -10 dBV INPUTS

SIDECHAIN INSERT

TIP=INPUT RING=OUTPUT

CHANNEL 1

INPUT (BALANCED) Jacks: The Tip/Ring/Sleeve phone jack and XLR-type jack are wired in parallel; either INPUT will accept an audio signal for processing by the 166XL. The phone jack accepts a standard TRS 1/4 phone plug for a balanced input source, or a 2-circuit (Tip/Sleeve) 1/4 phone plug for an unbalanced source. The XLR-type jack is wired pin 2 HOT (+), pin 3 COLD (-) and pin 1 GROUND.
Note: Only one input jack should be used at a time, except for splitter applications where one input jack is used as an input and the other input jack is used as an output (see Using the SIDECHAIN INSERT section on page 16). Since a given pair of channel input jacks (e.g., Channel 1 XLR INPUT and Channel 1 1/4 INPUT) are internally connected (TIP = Pin 2, RING = Pin 3, SLEEVE = Pin 1), if one of the jacks is unbalanced, then the other jack will be unbalanced. For example, if a 1/4 INPUT jack is used with a mono cable, and is therefore unbalanced, the XLR INPUT jack will also be unbalanced (Pin 3 shorted to ground).
OPERATING LEVEL Switch: This switch selects between a -10dBV and +4dBu nominal operating level. When the switch is in the in position, a -10dBV operating level is selected. When it is in the out position +4dBu is selected. A -10dBV operating level should be
selected when interfacing with semi-pro or low level equipment, while a +4dBu level should be selected when interfacing with pro equipment. The switch simultaneously changes the operating levels for both the input and output circuits. Note that the switch is slightly recessed to prevent accidental switching of operating levels while plugging in or unplugging cables. OUTPUT (BALANCED) Jacks: The Tip/Ring/Sleeve phone jack and XLR-type jack are wired in parallel; either OUTPUT will send an audio signal to a load. The phone jack accepts a standard TRS 1/4 phone plug for a balanced output load, or a 2-circuit (Tip/Sleeve) 1/4 phone plug for an unbalanced load. The XLR-type jack is wired pin 2 HOT(+), pin 3 COLD (-) and pin 1 GROUND. For proper unbalanced operation, the unused pin (either pin 2 or 3) must be grounded. Nominal output signal level is +4dBu or -10dBV into 600, and typical maximum output level is +20dBu into 600 (+20dBm).

These types of settings are most useful for tightening up drum tracks, removing the ring from some drums, or gating out the leakage of one drum through anothers mic.
Gating Sounds That Have Longer Decay (e.g., Cymbal, Piano)
To effectively gate sounds which have more decay after the initial transient, set the RELEASE control slow enough to allow the gate to remain open and capture the signals entire envelope. The gate can also be used to dry up a track or mix that has too much reverb or ambience. Set the RELEASE control so that the natural decay of the sound is somewhat truncated.

Changing Sound Quality

The 166XLs gate can effectively change the sonic character of a sound because it can reduce or otherwise alter the quality of instrumental ambience and reverb. For example, as an instrument stops, its reverberation level will fall through the 166XLs THRESHOLD setting. It can now be made to die out more quickly - faster than the natural decay (of the sound). Experiment with different THRESHOLD and RELEASE settings to change the tail of the sound; a FAST RELEASE setting will nearly eliminate reverb.

Keyed Gating

Keyed gating, that is, controlling the gating of one signal by another, can be used to add dynamics to a sound (e.g., cre-
dbx 166XL COMPRESSOR / GATE ating perfectly in-sync playing and overdubbing among individual instruments or fattening a dynamically weak track). To create two distinct channels of bass guitar for your mix (by splitting the bass signal into two channels and synchronizing one channel of bass guitar with the kick drum), start by feeding one channel of bass directly into the mix and the other into the 166XLs INPUT. Then key the gate with a signal from the kick drum (connected to the SIDECHAIN INSERT - adjust controls as needed). The gated bass track will now open with each kick, adding punch and dynamics. This can really tighten up the tracks and add life to the mix. Another example of keyed gating is using the drum signal to key an oscillator which is set to an appropriate frequency to tune and punch up the drum sound.
Note: For all keyed gating applications, be aware to adjust the compressor accordingly or bypass it by setting the Compressor RATIO fully counterclockwise to 1:1

Raising Average Level in PA Systems
Limiting (i.e., compression at high ratios like :1) also benefits intelligibility by allowing low-level input signals to be reproduced through the system at higher volume. In a musical performance, this provides additional intimacy so that a
dbx 166XL COMPRESSOR / GATE vocalists whispers are heard more clearly. The OverEasy curve available with the 166XL permits a very high amount of compression (RATIO of 10:1 or greater) to be used in many situations. This allows dynamic speakers, vocalists and other musicians to concentrate on their presentation or performance without worrying about the ill effects of volume changes.
Using Your EQ to Reduce Feedback in Live Settings (Indoor and Outdoor Concerts, Churches)
You can use your 166XL and EQ (equalizer) to reduce feedback in clubs, churches, outdoor concerts and other live settings. Patch or insert the 166XL into the main output of a mixer, set the 166XL to Hard Knee mode and slowly increase OUTPUT GAIN until the first feedback ring occurs, then set up the 166XL with its RATIO at :1 and THRESHOLD low. The 166XL will catch the first feedback ring and hold it as a constant tone so you can adjust your EQ to minimize it. Continue to increase your console gain and set your EQ until the next 3 or 4 ring frequencies have been compensated for.
The 166XL as a Line Amplifier
To use the 166XL as a line amplifier, adjust the RATIO control fully counterclockwise (1:1 position), THRESHOLD fully clockwise (+20), PeakStop to +20 and OUTPUT GAIN to whatever setting is required for the application. Remember, excessive gain may lead to output clipping of high level signals. To add compression, adjust the RATIO and the THRESHOLD controls to the desired settings.
Frequency-Weighted Compression (Sidechain Application)
It is possible to separate certain vocals and instruments from a mix by frequency-weighted compression. With an equalizer (such as a dbx 20 Series or 30 Series EQ) inline ahead of the SIDECHAIN INSERT (but not in the audio path), the equalization settings do not shift the timbre or frequency response of the audio signal. They merely alter the threshold response of the compressor on a frequency-weighted basis. With this arrangement, raising certain frequencies on the equalizer causes them to be suppressed in the audio signal. A relatively high THRESHOLD setting can allow normal sounds to be unaffected while solo and very loud sounds are compressed. (Of course, when compression occurs, the level of the entire program is affected - however, if the 166XLs CONTOUR button is pressed in, even more of the signals lower energy can be preserved.) Depending on the THRESHOLD setting, lower amplitude fundamentals or harmonics will not cause compression, and the program is not subject to the phase shift normally caused by program equalization. 166XL 166A

INPUT OUTPUT SIDECHAIN INSERT

OUTPUT SOURCE

Figure 3: Frequency-Weighted Compression
When recording cymbals and tom-toms, a compressor with an equalizer in the Sidechain path can help prevent analog tape saturation. The equalizer can be adjusted for boost with a peak of about 5kHz, causing the cymbal to be compressed on a very loud crash, stopping tape saturation at high frequencies, where there is less headroom. However, gentle tapping of a drumstick or brushing of the cymbal will not be affected. Assuming the tom-tom is a lower frequency instrument and can be better tolerated by the tape, it has less need for compression. Equalization in the Sidechain circuit means that the compressor is not triggered as readily by a loud tom-tom beat as by an equally loud cymbal crash. The converse of the above EQ technique may be used: dipping the equalizer bands causes any sound with dominant energy in the affected register to pull the level up because the 166XL will detect a need for less compression.

De-Essing

To apply de-essing to vocals (i.e., a reduction of sibilance), use a parametric equalizer (e.g., a dbx 242) in the SIDECHAIN circuit and set it to boost the specific frequency range where the vocal hiss or lisp occurs (generally in the 4kHz - 6kHz region). This pre-emphasizes the already hissy vocal input to the Sidechain. Used in conjunction with a moderate to high THRESHOLD and RATIO, and a fast Attack and Release setting, this arrangement greatly attenuates the essing without affecting the basic sound quality or balance of the voice. While it is true that all frequencies are lowered in level when the compressor is triggered, generally the sss sound occurs alone, before or after the dominant tone in the voice.

Increasing Sustain

To increase the sustain of a musical instrument (e.g., a guitar or bass), use an equalizer in the Sidechain circuit and boost the EQ in the dominant frequency range of the instrument. Set the 166XL for slow Hard Knee compression, with a fairly low THRESHOLD and a moderate RATIO.
Multi-Way Speaker Systems
If a single compressor is to be used with a multi-way speaker system (i.e., before the crossover, after the EQ), the system operator is faced with the problem of keeping levels below the point of damage of the most sensitive part of the system. If, for example, mid-range drivers are frequently damaged, the whole system must be operated at a lower sound-pressure level, or additional mid-range drivers must be added. By inserting an equalizer in the Sidechain path to the 166XL, it can be made more sensitive to frequencies in the range handled by the sensitive drivers. The system can then be run at higher levels and will only be dropped back when damaging signals are present.

Using a Filter in the Sidechain Circuit
The results of inserting a filter in the Sidechain circuit are basically the same as obtained with an equalizer, as previously described. Those frequencies passed by the filter are subject to compression (or at least they are subject to considerably more compression than those frequencies outside the passband). Because a passive filter can have insertion loss, it may be necessary to lower the 166XLs THRESHOLD setting to maintain a given amount of gain reduction within the filter passband; this can be determined by monitoring the 166XLs THRESHOLD LEDs.
Pre-Emphasis for Broadcast Applications
By inserting a pre-emphasis filter network in the Sidechain path of a 166XL processing pre-emphasized audio, higher levels can be run within the headroom limitations of the broadcast chain.
CONNECTING THE 166XL TO YOUR SYSTEM

Basic Connection

15 WATTS PROFESSIONAL PRODUCTS A HARMAN INTERNATIONAL COMPANY SALT LAKE CITY, UTAH MADE IN USA MODEL 166XL COMPRESSOR/LIMITER/GATE
The 166XL has balanced inputs and outputs, and can be used with any line-level device. Some common examples include: mixing consoles, musical instruments, patch bays and other signal processors. For more specific cabling information, refer to Installation Considerations, page 18. For all connections, refer to the following steps: 1. Turn Off all equipment before making any connections. 2. Mount the 166XL in a 1U rack space (Optional). The 166XL requires one rack space (height) and 1 rack space (width). It can be mounted above or below anything that doesnt generate heat, since it requires no special ventilation. Ambient temperatures should not exceed 113F when equipment is powered.
Caution: Never remove the cover. There are no user-serviceable parts inside, and you run the risk of an electric shock.
3. Make connections via XLR or 1/4 TRS jacks according to your requirements. Typical patch points include: a mixers channel or subgroup inserts when using the 166XL on individual instruments or tracks; the mixers main outputs or bus inserts when mixing; an instrument preamps effects loop when using the 166XL for guitar or bass; main outs of a submixer (e.g., keyboard mixer) as the signal is sent to main mixer; between a DATs output and an analog cassette input. When using a chain of processors, the 166XL may be placed either before or after effects or dynamic processors. However, if you are using the 166XL for speaker protection, the compressor should be as close to the amplifier as possible in the signal chain. We recommend you use common sense and experiment with different setups to see which one provides the best results for your needs.

Note: Never connect the 166XLs input to the speaker output of an instrument or power amplifier.
4. Power On the unit: Securely connect the AC power cord to the unit and mains power.
Note: Check the line voltage. The unit is shipped for 115V or 230V operation. Refer to the units rear panel to verify your units precise line voltage.
Using the SIDECHAIN INSERT
The SIDECHAIN INSERT can be used to control the compressor or the expander/gate by signals other than the audio input (via an auxiliary device, such as an equalizer). Common Sidechain applications include keyed gating, frequency-sensitive gating and frequency-weighted compression. These topics are covered in detail in the previous pages of this manual. Certain Sidechain applications may require special cabling. For example, to set up your 166XL for frequency-sensitive gating or frequency-weighted compression, you must feed an equalizers input with the same signal fed to the 166XLs INPUT, and then connect the equalizers output to the 166XLs SIDECHAIN INSERT jack (Figure 3). Providing the signal to both the 166XLs INPUT and the equalizer can be accomplished in several different ways: (1) use an insert cable plugged into the SIDECHAIN INSERT jack. The SEND goes to the input of the EQ. The RETURN goes to the output of the EQ; (2) use a Y-cable to feed the audio source to both the 166XL INPUT and the equalizer input; (3) feed the signal to one of the 166XLs INPUT jacks and use the compressor channels parallel INPUT jack to drive the equalizer (e.g., if the audio source feeds into Channel 1s 1/4 INPUT jack, use Channel 1s XLR INPUT jack to feed the signal to the equalizer); (4) if the audio source can internally split its output signal (e.g., some synthesizers can send the same signal from two outputs), plug a cable into each output and feed one cable to the 166XL INPUT and the other to the equalizer.
Specific System Connections
The 166XL has balanced inputs and outputs, and can be used with any balanced or unbalanced line-level device. Some common examples include: mixing consoles, musical instruments, patch bays, and other signal processors.

Mixing Board

If you wish to compress a particular track of a multitrack recording or one channel of a live performance, connect the 166XL INPUT to the audio sources output jack while the 166XL OUTPUT can be directly connected to a line input jack (balanced or not) or the 166XLs INPUT and OUTPUT can be wired to an Insert point. In the latter case, the signals will most likely be unbalanced. It is important to note that the amount of compression is directly related to the level of the input signal. However, depending upon your systems setup, it may not always be clear as to what volume controls in your chain affect input level and which affect output level. If the 166XL is connected so that compression occurs before the mixers volume controls (e.g., the 166XL is connected directly between an audio source and the mixer input, or the 166XL is connected to mixer inserts that are pre-fader), you can boost or cut the input level by adjusting the sources volume control (e.g., a synthesizers volume control) and boost the tracks output level using the 166XLs OUTPUT GAIN control or the mixers volume fader (the latter here is great for track fade-outs). However, if the 166XL is connected to post fader mixer inserts, adjusting the mixers volume fader changes the input level and the amount of compression. If you would rather have this volume fader control output, we suggest that you set up the compressor directly between the source and the mixer channels input. This way, you can use the instruments volume control to define the input level and amount of compression and the mixers volume fader to change only the overall volume of the track.

Musical Instruments (e.g., Electric Guitar, Bass, Keyboards, Electric-Acoustic Instruments)
The output of an electric guitar is sometimes not hot enough to drive the 166XLs INPUT. When this is the case, switch the rear panel +4/-10 switch to the IN position which will boost the low level signal by approximately 12dB. If this is still not enough boost then you should use the PREAMP OUT of your guitar amp (if so equipped), or the output of some other device that is designed to accept low-level instrument inputs (including various foot pedal effects, acoustic pickup preamps, and some rack mount audio products). Such sources can be balanced or unbalanced - this is no problem for the 166XL. Microphones, bass guitars, and electric-acoustic instruments, also typically have low-level outputs. With most setups they require signal boost to drive the 166XLs INPUT. For example, when recording voice directly to a portable tape deck, a mic preamp placed between the mic and the 166XL (which is then fed to one of the recorders inputs) can boost the signal for the 166XL as well as provide a high level signal to the tape deck. Keyboards, samplers, drum machines and sound modules typically produce a line-level signal and can be connected directly from the instruments output to the 166XLs INPUT.
Note: DO NOT CONNECT the 166XLs input to the speaker output of an instrument or power amplifier. Severe damage to system components may result.

Patch Bay

In the studio, the 166XL may be connected to a patch bay (such as a dbx PB-48) to allow it to be used anywhere in the studio system. If your studio is not fully balanced, you must ground the unused balanced output conductor: XLR pin (either pin 2 or 3) or the ring of a 1/4 stereo phone jack. Note that grounding pin 2 of the XLR jack reverses the phase through the 166XL.

Sound Reinforcement

To compress a live mix or to protect loudspeakers, connect the 166XL between the source (mixing board or distribution amp) and the power amp(s). If multi-way loudspeakers with low-level electronic crossovers are used, the 166XL(s) should go after the crossover(s). For a stereo system, you can separately stereo couple the two high band crossovers, low band crossovers, etc. If limitations require that you use a single 166XL channel before a crossover, adding an equalizer to the sidechain may provide some additional protection to your high frequency components (see Speaker Protection, page 8).

INSTALLATION CONSIDERATIONS
Input/Output Cable Configurations

Hookups and Cabling

The 166XL is a balanced (differential) unit designed for nominal +4dBu or -10dBV levels; inputs and outputs are 1/4 tip/ring/sleeve (TRS) phone jacks and XLR-type jacks. The 166XL can be used with either balanced or unbalanced sources and outputs can be used with either balanced or unbalanced loads, provided you use proper cabling. A balanced line is defined as two-conductor shielded cable with the two center conductors carrying the same signal but of opposite polarity with respect to ground. An unbalanced line is generally a single-conductor shielded cable with the center conductor carrying the signal and the shield at ground potential.
Input Cable Configurations
The 166XL has an actual input impedance of >40k in balanced or unbalanced configurations. This makes the 166XL audio input suitable for use with virtually any source impedance, low or high. The 166XLs input jacks are wired in parallel. The phone jack TIP (+) connection is internally wired to the XLR pin 2, the RING (-) is wired to pin 3, and the SLEEVE (shield) is wired to pin 1. Note that pins 2 and 3 are the reverse of certain older dbx and other manufacturers equipment, but if the same connection is used at both the input and the output, the signal will be correctly polarized (in phase). Reversing the input wires to the input terminals will result in the output signal polarity being the opposite of the input signal (180 out of phase).
Output Cable Considerations
The model 166XLs outputs are wired in parallel: either the XLR-type OUTPUT jack or the 1/4 stereo phone jack are capable of driving a 600 load. The phone jack TIP (+) connection is internally wired to the XLR pin 2, the RING (-) is wired to pin 3, and the SLEEVE (shield) is wired to pin 1. Note that pins 2 and 3 are the reverse of certain older dbx and other manufacturers equipment, but if the same connection is used at both the input and the output, the signal will be correctly polarized (in phase).

166XL 166A

SIGNAL FLOW
Figure 4: Signal Flow (Balanced Connection)

Grounding

For maximum hum rejection with a balanced source, avoid common grounding at the 166XLs input and output. Most balanced (3-conductor) cables have the shield connected at both ends. This can result in ground loops which cause hum. If hum is a problem, try disconnecting the shield on one or more of your cables, preferably at the input of a device, not at the output: Ground the shield of the input cable at the source device (leaving it unconnected at the 166XLs INPUT) and ground the shield of the output cable to the ground terminal of the 166XL (leaving it unconnected at the receiving device). The shield is pin 1 on the XLR, SLEEVE on a 1/4 TRS.
TECHNICAL SUPPORT, FACTORY SERVICE
The 166XL is an all-solid-state product with components chosen for high performance and excellent reliability. Each 166XL is designed, assembled, tested, burned in and calibrated at the factory in the USA and should require no internal adjustment of any type throughout the life of the unit. We recommend that your 166XL be returned to the factory only after referring to the manual and consulting with Customer Service. Our phone number, fax number and address are listed on the rear cover. When you contact dbx Customer Service, be

Impedance Maximum Level CMRR
Sidechain Insert (1/4 TRS Phone) Circuit d'insertion Sidechain (Jack 6,35 tripolaire) Sidechain-Einsatz (1/4 TRS-Telefon) Sidechain (circuito de insercin) (tripolar de 0,5 de pulgada)
>50k balanced, >25k unbalanced +24dBu, Balanced or Unbalanced >40dB at 1kHz, typically >55dB
Normalled: Ring = Output (send); Tip = Input (return)

Impedance Maximum Level

Outputs (1/4 TRS Phone and XLR) Sorties (Jack 6,35 tripolaire et XLR) Ausgnge (1/4 TRS-Telefon und XLR) Salidas (tripolar telefnico de 0,25 de pulgada y XRL)
Tip = >10k (Input) Ring = 2k (Output) +24dBu
Floating Balanced; XLR: Pin 2 and TIP HI Symtriques flottantes; signal (+) = broche 2 (XLR) et pointe (Jack) differential ausgeglichen; XLR: Stift 2 und TIP HI Simtricas flotantes; seal (+) = clavija 2 (XLR)
Impedance Maximum Level Frequency Response Noise THD+ N SMPTE IMD
Compressor Circuit de compression Dynamikregelung Circuito de compresin
120 balanced, 60 unbalanced +21dBu,>+20 dBm into 600, balanced or unbalanced 20Hz - 20kHz; +0, -0.5dB,Typical 3dB points are 0.35Hz and 110kHz, unity gain <-90dBu, 22Hz to 22kHz, no weighting, unity gain Typically <0.04%; Any Amount of Compression Up to 40dB@1kHz Typically <0.08% @ +10dBu (15dB Gain reduction)
Threshold Range Threshold Characteristic Compression Ratio Attack Time Release Rate
Expander/Gate Circuit expanseur/porte Expander/Torschaltung Circuito expansor/compuerta
-40dBu to +20dBu Selectable OverEasy or Hard Knee Variable; 1:1 to Infinity:1; 60dB Maximum Compression Variable program-dependent; 3ms to 340ms for 15dB gain reduction Variable program-dependent; 200dB/Sec to 3dB/Sec
Threshold Range Expansion Ratio Maximum Depth Attack Time Release Time
PeakStop Limiter Limiteur PeakStop PeakStop-Begrenzer Limitador de crestas PeakStop*
OFF to +15dBu 10:1 >60dB <500s (from Maximum Depth) Adjustable, 30ms to 3sec (to 30dB attenuation)

Threshold Range

Gain Adjustment Range Gamme de rglage du gain Dynamikregelung-Einstellbereich Margen de ajuste de ganancia Interchannel Crosstalk Diaphonie Zwischenkanal-Kreuzkopplung Intercomunicacin de canales

0dBu to +20dBu

Variable; -20dB to +20dB

<-80dB, 20Hz to 20kHz

Dynamic Range Gamme dynamique Dynamikbereich Margen dinmico Stereo Coupling Couplage stro Stereokopplung Acoplamiento estereofnico Operating Voltage Tension d'alimentation secteur Betriebsspannung Tensin de operacin

>115 dB

True RMS Power Summing
100 VAC 50/60Hz; 120VAC 60Hz 230 VAC 50/60 Hz
Power Consumption Consommation lectrique Leistung Consumo de energa Operating Temperature Temprature de fonctionnement Betriebstemperatur Temperatura de operacin Dimensions (H x W x D) Encombrement (h x l x p) Abmessungen (H x B x T) Dimensiones (Altura x Ancho x Profundidad) Rack Space Espace baie ncessaire Rackraum Espacio de instalacin Weight Poids Gewicht Peso