Overview: The dbx 1231 dual 31-band graphic equalizer, part
of the 12-series EQs, is a precision-engineered,
professional-quality EQ with simple, straight-forward controls. From the
magnetically isolated power transformer to the RF-filtered inputs and outputs,
the 1231 is designed for years of maintenance-free operations. The 1231 features two
independent channels and 31 frequency bands, broken down in 1/3-octaves. Each
non-conductive slider has approximately 45mm of movement with a detent at the 0
(flat) position. The 1231 fits neatly into a standard equipment rack (3U space
required), and includes 4 rack mount screws and washers.
Input Gain: The 1231 is equipped with a rotary input gain control to set the
signal level to the equalizer. The input gain control has a range of -12dB to
+12dB. You can monitor the input to the EQ through the 4-LED Output Level Bar
Graph, which has green (-10dB, 0dB), yellow (+10dB), and red (+18dB--3dB below
clipping) indicators. There is also a red LED
to indicate if the input signal is clipping. The 1231 has independent input gain
controls for each channel.
Frequency Bands: The 1231 includes the following frequency bands
at ISO standard spacings: 20Hz, 25Hz,
31.5Hz, 40Hz, 50Hz, 63Hz, 80Hz, 100Hz, 125Hz, 160Hz, 200Hz, 250Hz, 315Hz, 400Hz,
500Hz, 630Hz, 800Hz, 1kHz, 1.25Hz, 1.6Hz, 2kHz, 2.5kHz, 3.15kHz, 4kHz, 5kHz,
6.3kHz, 8kHz, 10kHz, 12.5Hz, 16kHz, and 20kHz.
Switchable Boost/Cut Range: The dbx 1231 has a maximum boost/cut range of +/-
15dB. If desired, you can switch to a range of +/- 6dB. This gives you finer
control within the range. The boost/cut range switch is located on the front
panel, and is recessed to prevent accidental activation of the switch, possibly
causing damage to other sound system components. LEDs indicate which boost/cut
range is selected (red for +/- 15dB and yellow for +/- 6dB). There are Boost/Cut Range switches for each channel.
Low Cut: To instantly cut out low frequencies, you can engage the built-in
Bessel 40Hz 18dB/octave low cut filter. The Low Cut switch is located on the front
panel, with an LED that glows red when the filter activated. The Low Cut
switches are recessed to prevent accidental activation of the switch, and are
provided for each channel.
EQ Bypass: Each channel has an EQ Bypass switch, which bypasses the graphic
equalizer section in the signal path, when activated. An EQ Bypass switch is
provided for each channel, with a red LED that glows when the switch is engaged.
Note: When the EQ bypass is activated, only the graphic equalizer
section is effected. The input gain and low cut filters remain unaffected
when the EQ is bypassed.
Inputs: The dbx 1231 is equipped with a 1/4" TRS (tip/ring/sleeve) phone jack
and a female locking XLR (pin 2 hot) input connector for each channel. It also
includes a barrier strip for hard-wiring the input cable. Each
input can accept balanced or unbalanced input sources. The maximum acceptable
input level is typically +22dBu (ref: 0.775Vrms).
Outputs: Each channel has a 1/4" TRS phone jack and a male XLR output
connector. They also include a barrier strip for hard-wiring the output cable. The outputs can be used with either balanced or unbalanced loads. The
maximum output level is greater than +21 dBu balanced/unbalanced into 2 kΩ
or greater, >+18 dBm balanced/unbalanced (into 600Ω).
AC Power: The 1231 has a 3-pin IEC power cord receptacle,
and comes with a 7-foot AC power cord.
- Frequency Response: <10 Hz to >50 kHz, +0.5/-3 dB
- Bandwidth: 20 Hz to 20 kHz, +0.5/-1 dB
- Dynamic Range: 109 dB (+/-15dB range), 115 dB (+/-6dB
- Signal-to-Noise: 90 dB (+/-15dB range), 97 dB (+/-6dB
- THD+Noise: <0.005%
- Interchannel Crosstalk: <-80 dB, 20 Hz to 20 kHz
- Input Impedance: Balanced 40 kΩ, Unbalanced 20 kΩ
- Output Impedance: Balanced 200 Ω, Unbalanced 100 Ω