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3. GENERAL DESCRIPTION
The E-1231 is a single channel, 1/3 octave active graphic equalizer designed to allow clean, accurate audio
equalization for stage, studio, or commercial applications.
The E-1231 provides 12 dB of boost or cut at each of its 28 frequencies, which are centered at ISO 1/3 octave
increments from 31.5 Hz to 16 kHz.
The E-1231's active bandpass/bandreject filters are designed for minimum phase shift, and feature smooth
slide controls with center detents for easy and accurate adjustment. (The filters are summed in parallel for
reliability, so that the failure of one filter does not interrupt operation of the others.)
In addition, continuously variable highpass filters are provided on the front panel. The highpass filter has a
slope of 12 dB per octave and is variable from 15 Hz to 300 Hz, while the lowpass filter can set for either a 6
dB per octave slope or a 12 dB per octave slope and is variable from 2.5 kHz to 30 kHz.
An input level control on the E-1231 gives ±12 dB of adjustment to allow a wide variety of input sources. A
LED indicator illuminates when either the input or the output comes within 3 dB of clipping. In addition to the
usual EQ in/out switch, an automatic EQ bypass function provides complete equalization bypass in the event
of loss of AC power, and an output muting function suppresses turn-on/turn-off transients.
A security cover is included with the E-1231 to guard against accidental disturbance, or intentional tampering
when used in fixed installations.
The E-1231 can be mounted in a standard 19" rack and occupies 3-1/2" of vertical space.
4. FEATURES
• 12 dB boost or cut at each center frequency, continuously variable.
• High quality, low phase-shift active filters.
• Precision calibrated, noiseless slide controls with center detent.
• Equalizer In/Out switch.
• Continuously variable highpass and lowpass filters.
• LED peak indicator to detect clipping at input or output levels.
• Variable input level control to accept variety of input sources.
• Automatic EQ bypass circuitry.
• A security cover is included.
• Filter In/Out switch
• Lowpass filter can be set for either 6 dB/oct or 12 dB/oct.
5. HANDLING PRECAUTIONS
• Do not operate the E-1231 from power mains which exceeds the indicated mains voltage by more than 10%.
• When cleaning the unit, be sure to turn the power switch to OFF. Wipe with a soft dry cloth. If it gets very
dirty, use the soft cloth slightly moistened in neutral cleanser. Never use thinner, benzene, chemically
processed towels, or alcohol as the unit’s plastic or other parts may be deformed or discolored.
