audio signal coupling capacitors are tight tolerance, quiet,
multi-layer and metallized polyester film type. The
transistors utilized in the audio signal path are popular low
noise audiophile grade 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 DC power adapter. This allows the
audio 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
OPTI-
FET Compressor 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.
Features:
THRESHOLD, RATIO, ATTACK, RELEASE and GAIN controls.
The control ranges for the ATTACK and RELEASE have been
optimized for use on both bass and guitar.
The compressor exhibits 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 compressor side-chain utilizes precision full-wave
rectification of the audio signals in the THRESHOLD circuit
for accurate envelope tracking. This also reduces the
possibility of “pumping” with very low frequencies.
ACTIVATE foot switch places the compressor unit in the
signal chain or in Direct Bypass mode. In Direct Bypass
mode the signal at the input is directly connected to the
output and does not pass through any electronics.
EQUALIZER foot switch enables the three band equalizer
controls for the side-chain control circuit. The three band EQ
only affects the amplitude of frequencies of the signal in the
side-chain control circuit to modify threshold sensitivity by
frequency band.
LOOP SEND/RETURN jacks are for placing external
processors or EQ’s in the compressor side-chain control
circuit. These jacks are only active when the EQUALIZER
foot switch is enabled.
Internal DIP switches to select the output amplifier mode of
operation. The three modes are clean (SW 1&2 off), warm 1
(SW 1 on) and warm 2 (SW 2 on). The warm 2 mode adds a
subtle amount more of the dynamic harmonics of mode 1.
Internal DIP switch for a 12KHz filter for an ‘old school’ tone
or to reduce the hiss from pedals proceeding the
compressor.
The audio signal compression is accomplished with only a
resistive component (Light Dependent Resistor or Photocell).
All resistors in the circuit are low noise metal film type. The
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