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-sen-
sitive 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 equalizer’s input with the same signal fed to the 166XL’s INPUT, and then connect the equalizer’s output to the
166XL’s SIDECHAIN INSERT jack (Figure 3). Providing the signal to both the 166XL’s 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 166XL’s INPUT jacks and use the compressor
channel’s parallel INPUT jack to drive the equalizer (e.g., if the audio source feeds into Channel 1’s 1/4” INPUT jack, use
Channel 1’s XLR INPUT jack to feed the signal to the equalizer); (4) if the audio source can internally split its output sig-
nal (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 source’s output jack while the 166XL OUTPUT can be directly connected to a line input jack
(balanced or not) or the 166XL’s 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 system’s 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 mixer’s 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 source’s volume control (e.g., a synthe-
sizer’s volume control) and boost the track’s output level using the 166XL’s OUTPUT GAIN control or the mixer’s vol-
ume fader (the latter here is great for track fade-outs). However, if the 166XL is connected to “post fader” mixer inserts,
adjusting the mixer’s 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 chan-
nel’s input. This way, you can use the instrument’s volume control to define the input level and amount of compression
and the mixer’s 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 166XL’s INPUT. When this is the case,
switch the rear panel +4/-10 switch to the INposition 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 166XL’s 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 recorder’s inputs) can boost the sig-
nal 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 instrument’s output to the 166XL’s INPUT.
Note:DO NOT CONNECT the 166XL’s 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.
dbx 166XL COMPRESSOR / GATE
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