User guide

664 User Guide and Technical Information
10
v. 1.0 Features and specifications are subject to change. Visit www.sounddevices.com for the latest documentation.
Input Fader
The Input Fader is the primary control used while mixing and it aff ects
the level of the Input signal routed to all post-fade destinations. Use the
Input Fader to make fi ne gain adjustments. The fader can be a enuated
from off (full counter-clockwise position) to +15 dB above the set Trim
level (full clockwise position). To optimize gain structure for the best per-
formance, operate input faders at or near the 0 dB (unity gain) position.
High-Pass Filter
Each input channel has an adjustable high-pass fi lter controlled by the High-Pass Filter control. High-
pass (or low-cut/low roll-off ) fi lters are useful for removing excess low
frequency energy from audio signals. Wind noise is a common unwanted
low frequency signal that can be reduced with the use of a high-pass fi lter.
For most audio applications, engaging the high-pass fi lter is benefi cial, be-
cause audio information below 100 Hz is rarely used, especially for speech
reproduction.
The 664’s high-pass fi lter circuit features an adjustable corner (-3 dB) fre-
quency over a range from 80 to 240 Hz. Below 80 Hz, the fi lter’s slope is 12
dB/octave. At higher corner frequency se ings, the slope is 6 dB/octave. The
purpose for this compound slope is to give additional roll-off at the 80 Hz
se ing to reduce wind noise and low frequency rumble. The higher se ings
can be used to counteract the proximity eff ect of directional microphones where a more gentle slope is
desired.
The 664’s high-pass fi lter circuit is unique because of its placement before any electronic amplifi cation.
Most mixers’ high-pass fi lter circuits are placed after the microphone preamplifi er, such that all of the
low-frequency signals get amplifi ed. By virtue of the 664’s circuit cu ing the low-frequency signals
before amplifi cation, higher headroom is achieved in the presence of signals with signifi cant low-
frequency energy.
When possible, a empt to equalize at the sound source with microphone selection, placement, wind-
screens, and onboard microphone fi ltering. Many microphones have on-board high pass fi lters. Use
the high-pass fi lters on the 664 in conjunction with the microphone’s fi lter to increase the fi lter’s slope.
The fi lter can be removed from the circuit completely by rotating the high-pass fi lter control to the full
counter-clockwise (detented) position. The high-pass fi lter potentiometer can be adjusted easily and
then recessed to hide it from the mixing surface.
Pan Control
The pop-up Pan Control routes inputs to the left (L) and right (R)
channels of the stereo Master Bus. The pan pot has a detent in the
center position. After se ing the pan, the pan control can be recessed
to hide it from the mixing surface during normal operation.