components (Light Dependent Resistors or Photocell). All
resistors in the circuit are low noise 1% metal film type. The
signal coupling capacitors are tight tolerance, quiet, multi-
layer and metalized polyester film type. The amplifiers used
in the signal path are JFET input, low-noise, low-distortion
“hi-fi quality” devices.
The power supplies onboard voltage charge pump allows
the circuitry to operate at 18volts (+9 and
–9 volt rails) from
a single 9 volt battery or 9 volt DC power adapter. This
allows the signal plenty of headroom from active electronic
guitars and aggressive playing techniques (i.e. pop and
slap).
The “switch on” power supply current is less than 1µA
(micro amp) on the signal ground at the INPUT jack. This is
approximately 45,000 times (-93dB) less than the commonly
used method of connecting the battery’s negative terminal
to ground via the sleeve of the plug inserted into the INPUT
jack. The “switch on” sensing method used in the FEA
Dual-Band Compressor-Limiter keeps nearly all of the
circuit’s generated white noise and transient currents out of
the INPUT stage signal ground. Extreme measures have
been taken to keep the power and signal paths as clean as
possible. NOTE: Unplug the cord from the INPUT jack when
not in use to prolong battery life.
The power and grounds for the signal path circuitry are
separated from the side-chain power and grounds to
protect the audio signal from spurious noise. The power for
the signal amplifiers is exceptionally clean, filtered twice for
each rail and all filter stages are oversized.
HI and LO/FULL output jacks are configured so the outputs
of the individual compressors may be routed to different
amplifiers or effects. The HI output is useful if you wish to
use effects made strictly for guitar and route a clean LO
signal to another amplifier or mixer. If only the LO/FULL
output jack is used, both the HI and LO signals are mixed
together for a composite full range output signal.
Features:
Dual optical compressors for separate Low frequency (LO)
and High frequency (HI) dynamics control.
Adjustable frequency crossover point with the range tailored
for bass guitar.
The frequencies above 5KHz are routed around the
compressor circuits and are mixed back into the output
amplifiers at unity gain to preserve clarity.
THRESHOLD, RATIO, ATTACK, RELEASE and GAIN controls
for the HI and LO compressors. The control ranges for the
ATTACK and RELEASE have been independently optimized
for the LO and HI bands.
Both bands exhibit soft-knee compression at lower RATIO
settings and hard-knee at maximum RATIO settings.
The
COMP LED indicates when the THRESHOLD has been
reached. This LED does not indicate the RELEASE
response.
The LIMITER switch changes the LO band compressor into a
LO band limiter. The LO RATIO control is bypassed and hard
limiting is applied and set by the THRESHOLD level control.
The compressor-limiter side-chains use precision full-wave
rectification of the audio signals in the THRESHOLD circuits
to improve tracking. This also reduces the possibility of
“pumping” with very low frequencies.
HI BYPASS foot switch. This allows the compressor-limiter to
only control the Low frequencies (if desired) and to pass the
High band frequencies to the outputs unaffected. There is a
red LED to indicate the HF BYPASS is on.
NOTE: With HI
BYPASS active the HI GAIN control is inactive.
ACTIVATE foot switch places the compressor-limiter unit in
the signal chain or in Direct Bypass mode. In Direct Bypass
mode the signal at the input is directly connected to the
outputs.
The compressors have minimal components in the signal
paths to maintain the utmost signal quality. The signal
compression-limiting is accomplished with only resistive
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