Art PRO Channel II User Manual
Pro Channel II™
Tube Preamp - Opto compressor - EQ
USER’S GUIDE
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IMPORTANT SAFETY INSTRUCTIONS – READ FIRST
This symbol, wherever it appears, This symbol, wherever it appears, alerts
alerts you to the presence of uninsulated you to important operating and maintenance
dangerous voltage inside the enclosure. Voltage instructions in the accompanying literature.
that may be sufficient to constitute a risk of shock. Please read manual.
Read instructions:
Retain these safety and operating instructions for future reference. Heed all warnings printed here and on the equipment.
Follow the operating instructions printed in this user guide.
Do not open:
Aside from one vacuum tube, there are no user serviceable parts inside. Refer any service work to qualified technical
personnel only.
Power sources:
Only connect the unit to mains power of the type marked on the rear panel. The power source must provide a good
ground connection.
Power cord:
Use the power cord with sealed mains plug appropriate for your local mains supply as provided with the equipment. If the
provided plug does not fit into your outlet consult your service agent. Route the power cord so that it is not likely to be
walked on, stretched or pinched by items placed upon or against.
Grounding:
Do not defeat the grounding and polarization means of the power cord plug. Do not remove or tamper with the ground
connection on the power cord.
Ventilation:
Do not obstruct the ventilation slots or position the unit where the air required for ventilation is impeded. If the unit is to be
operated in a rack, case or other furniture, ensure that it is constructed to allow adequate ventilation.
Moisture:
To reduce the risk of fire or electrical shock do not expose the unit to rain, moisture or use in damp or wet conditions. Do
not place a container of liquid on it, which may spill into any openings.
Heat:
Do not locate the unit in a place close to excessive heat or direct sunlight, as this could be a fire hazard. Locate the unit
away from any equipment, which produces heat such as: power supplies, power amplifiers and heaters.
Environment:
Protect from excessive dirt, dust, heat, and vibration when operating and storing. Avoid tobacco ash, drink spillage and
smoke, especially that associated with smoke machines.
Handling:
To prevent damage to the controls and cosmetics avoid rough handling and excessive vibration. Protect the controls from
damage during transit. Use adequate padding if you need to ship the unit. To avoid injury to yourself or damage to the
equipment take care when lifting, moving or carrying the unit.
Servicing:
Switch off the equipment and unplug the power cord immediately if it is exposed to moisture, spilled liquid, objects fallen
into opening, or the power cord or plug becomes damaged during a lightning storm or if smoke odor or noise is noted.
Refer servicing to qualified technical personnel only.
Installation:
Install the unit in accordance with the instructions printed in the user guide.
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Pro Channel II™
Tube Preamp - Opto compressor - EQ
IMPORTANT SAFETY INSTRUCTIONS – READ FIRST .......................................................................... 2
INTRODUCTION .................................................................................................................................... 4
INSTALLATION ..................................................................................................................................... 4
AC Power Hookup .................................................................................................................................................................................. 4
Analog Audio Connections ..................................................................................................................................................................... 4
FRONT PANEL CONTROLS and JACKS ................................................................................................ 5
Mic Preamp Controls .............................................................................................................................................................................. 5
Instrument Input ..................................................................................................................................................................................... 5
Gain Control ........................................................................................................................................................................................... 5
Impedance Control ................................................................................................................................................................................. 5
GAIN Switch ........................................................................................................................................................................................... 5
Phantom Power Switch .......................................................................................................................................................................... 5
Invert Switch ........................................................................................................................................................................................... 5
Low Cut Control ...................................................................................................................................................................................... 5
Preamp Output Control........................................................................................................................................................................... 5
Tube Voltage Switch .............................................................................................................................................................................. 6
Compressor Controls ............................................................................................................................................................................. 7
Threshold Control ................................................................................................................................................................................... 7
Attack Control ......................................................................................................................................................................................... 8
Release Control ...................................................................................................................................................................................... 8
Compressor Output Control .................................................................................................................................................................... 8
Gain Reduction LED Meter ..................................................................................................................................................................... 8
Semi-Parametric EQ .............................................................................................................................................................................. 9
EQ Bypass Switch .................................................................................................................................................................................. 9
CLIP LED ............................................................................................................................................................................................... 9
Master Output Control .......................................................................................................................................................................... 10
Output Meters ....................................................................................................................................................................................... 10
VU Meter Switches ............................................................................................................................................................................... 10
REAR PANEL CONNECTIONS ............................................................................................................. 12
INPUT Jack .......................................................................................................................................................................................... 12
PREAMP OUT Jack ............................................................................................................................................................................. 12
COMP IN Jack ...................................................................................................................................................................................... 12
COMP OUT Jack .................................................................................................................................................................................. 12
EQ IN Jack ........................................................................................................................................................................................... 13
OUTPUT Jacks .................................................................................................................................................................................... 13
OUTPUT LEVEL Switch ....................................................................................................................................................................... 13
APPLICATIONS ................................................................................................................................... 14
Bypassing Components Of The Pro Channel II™ ................................................................................................................................ 14
Optimizing The Preamp For Lowest Noise ........................................................................................................................................... 14
WARRANTY INFORMATION ................................................................................................................ 15
SERVICE ............................................................................................................................................. 16
SPECIFICATIONS ................................................................................................................................ 17
LIST OF FIGURES
FIGURE 1 – Preamp section
FIGURE 2 – Compressor Section
FIGURE 3 – Equalizer Section
FIGURE 4 – Signal Flow Block Diagram
FIGURE 5 – Output Section
FIGURE 6 - Rear Jacks
................................................................................................................. 6
.......................................................................................................... 7
.............................................................................................................. 9
............................................................................................. 10
................................................................................................................ 11
....................................................................................................................... 12
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INTRODUCTION
The ART Pro Channel II™ is the answer to your recording and computer audio interface needs. Our secondgeneration discrete Class-A microphone preamp provides clean quiet gain while maintaining incredible
transparency. A powerful dynamics processor subtly controls transients and noise of the most demanding
sources. The ART Pro Channel II™ ’s semi-parametric EQ offers wide tune-ability and can be patched before
OR after the dynamics processor. Separate insertion jacks allow you to use your favorite external signal
processing gear immediately after the Mic preamp and before the EQ and dynamics processor. Both analog
and LED meters provide a detailed indication of audio levels.
INSTALLATION
The ART Pro Channel II™ may be used in a wide variety of applications and environments. In a rackmountable, all-steel enclosure, the unit is designed for continuous professional use. Mounting location is not
critical, however for greater performance reliability we recommend that you not place the unit on top of power
amps, or other sources of heat and/or strong magnetic fields. The tube circuitry needs about a minute to “warm
up” and stabilize from a cold power up.
AC Power Hookup
The ART Pro Channel II™ has an internal power supply. Only connect the unit to mains power of the type
marked on the rear panel. The power source must provide a good ground connection, and the ground pin on
the mains plug should never be defeated.
Analog Audio Connections
Audio connections to and from the Pro Channel II™ are:
Front panel Instrument input: [1/4”] Tip = Hot (+), Sleeve = Ground
Rear panel balanced input: [XLR] Pin 2 = Hot (+), Pin 3 = Cold (-), Pin 1 = Ground
Rear panel balanced output: [XLR] Pin 2 = Hot (+), Pin 3 = Cold (-), Pin 1 = Ground
Rear panel 1/4” output: Tip = Hot (+), Ring = Cold (-), Sleeve = Ground
Rear panel 1/4” insert inputs: Tip = Hot (+), Sleeve = Ground
Insert Outputs: Tip = Hot (+), Sleeve = Ground
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FRONT PANEL CONTROLS and JACKS
Mic Preamp Controls
The Pro Channel II™ input consists of a discrete Class-A differential preamp. The circuit is optimized for low
impedance microphones as well as line level signals. Up to 56dB of gain is available from this stage. The
output can be inverted using the INVERT switch.
The impedance of the rear XLR input is continuously variable for fine-tuning the preamp to a wide variety of
mics. Phantom power is available on the XLR input as well.
A selectable low-cut filter removes rumble, wind noise, and pops, thereby increasing clarity.
Instrument Input
The 1/4” T/S jack on the front panel provides a high impedance unbalanced input, and when used,
automatically switches off the mic pre-amp. (The rear XLR balanced input is lower impedance and is part of the
mic pre-amp. The rear jack is not intended to be used with high impedance microphones or instruments.)
Gain Control
This control adjusts both the mic pre-amp gain as well as the instrument input gain. The gain marked applies
to the mic pre-amp without the GAIN switch depressed. Refer to the APPLICATIONS section to learn how to
optimize the gain control for low noise operation.
Impedance Control
This knob sets the load impedance at the rear panel XLR input of the Pro Channel II™. Use the IMPEDANCE
CONTROL to subtly tune the sound of your microphone. Various microphones will change their sound at
differing load impedances. The correct setting is subjective. Adjust this control to personal taste.
GAIN Switch
This switch increases the tube gain by 20dB to support low output mics and instruments. It should only be
used when the GAIN cotrol cannot provide enough gain.
Phantom Power Switch
The switch safely applies +48Volt phantom power to the XLR input. Use phantom power only when the
microphone that you are using requires it. Doing so will extend the life of the Pro Channel II
reducing the possibility of shock hazard.
as well as
Invert Switch
This switch selects the output phase of the Pro Channel II™. There is a 180 degree phase shift through the
Pro Channel II™ preamp section when lit.
Low Cut Control
This control allows adjustment of a 6dB/Oct high pass filter from 10Hz to 250 Hz. The filter is designed to
remove rumble, pops, and wind noise, yet still sound natural.
Preamp Output Control
This control adjusts the output of the Preamp section allowing up to 10dB of gain or allowing you to mute the
output when fully CCW.
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