Technical Specifications:
Crossover FREQ:
45Hz to 1KHz @ 12dB/Oct
ATTACK:
HI 2mS to 48mS
LO 2mS to 150mS
RELEASE:
HI 33mS to 533mS
LO 100mS to 1200mS
RATIO:
2:1 to 7:1 LIMITER:
:1
THRESHOLD:
-44dBu to
Make-up GAIN:
0 to 20dB
Maximum Input:
7.8dBu
Maximum Output:
13dBu
Residual Output Noise:
-66dBu from 10Hz-20kHz
(un-weighted) with no
compression and output gains set
to maximum. **This is the absolute
worst case noise scenario.**
Frequency Response:
10Hz
– 21KHz +1.25/-3dB
Input Impedance:
1M ohm
Output Impedance:
1K ohm
Power adapter
40dBu @ 60Hz
noise rejection:
>90dBu @ 2KHz
Current Consumption:
Approx. 36mA
Battery Life:
Approx. 11 hours continuous use
Power adapter (optional): 9VDC 2.1mm negative center pin
About the design:
Optical compressors are still preferred over VCA (voltage
controlled amplifier) compressors in most recording studios for
some instruments. One of those instruments where optical is
favored is on the bass guitar for its smooth attack and release
characteristics.
Optical compressors use a photocell (photo-resistive cell) and a
light source projected onto the photocell to vary the value of
resistance inversely proportional to the light intensity. Years
ago these were made with a discrete photocell and light
source. There are now devices that contain both the photocell
and light source in a single package. They are referred to as
Vactrols and AOI’s (analog optical isolators). The drawbacks of
these devices in the past have been with their reaction and
recovery times. If the photocell were formulated for a quick
reaction to light, the resistance would take a long time to settle
back after the light has been removed. The opposite is also
true; if the photocell were formulated for a quick recovery after
the light has been removed then the reaction to light would be
slow. The Luna Optoelectronics
™ Company (formerly
Silonex
™) uses a combination formula for the photocell to
overcome these limitations in the AOI that is used in the FEA
Dual Band Compressor Limiter or DB-CL. This very same AOI
is used in some high-end studio compressors for its smooth
attack and release qualities. This fast AOI allows the side-
chains in the compressor-limiter to accurately control the Attack
and Release times of the compression. The purely resistive
element in the AOI exhibits less noise and distortion than most
designs using a VCA. Most audiophiles advocate that only
good quality passive components should be in the audio signal
path and this is one application that I would have to agree with
them.
Along with these fantastic
AOI’s, the FEA DB-CL utilizes 1%
metal film resistors, multi-layer metalized polyester film
capacitors and hi-fi quality Texas Instrument
™ JFET
operational amplifiers in the signal paths. The input stage is a
high impedance CMOS, hi-fi operational amplifier buffer with
internal RFI protection. The input amplifier has been designed
to have minimal signal distortion and noise, with maximum
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