ART Pro Channel II
Introduction
The ART Pro Channel II™ is the answer to your recording and computer audio interface needs. Our second-generation 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 rack-mountable, 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
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 control 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™ as well as reducing the possibility of shock hazard.
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.
Tube Voltage Switch
The vacuum tube preamp section can be adjusted to run at two different plate voltages. Choose the "NORMAL" setting for adding warmth to the input signal, which has increased tube saturation at higher signal levels. Choose the "HIGH" setting to increase overall gain, headroom, and bandwidth. Note: The change between tube voltage modes is gradual, taking 10 to 20 seconds to be fully activated.
Compressor Controls
The ART Pro Channel II™ Compressor section consists of an above threshold Optical Compressor/Limiter with adjustable slope. The attack and release controls allow a wide range of adjustment while the complex detector assures fast response without distortion.
Threshold Control
This control sets the level, above which the Compressor in the Pro Channel II™ starts to act on the input signal. As the control is turned clockwise, more input signal is required to begin reducing gain. The compression action can be seen in the Gain Reduction LED meter.
Ratio Control
The RATIO control sets the amount of gain reduction that takes place based on how far the input signal is over the threshold level (set by the THRESHOLD control). A good starting point for vocals is 2.5:1. To have the unit act as a limiter, set the RATIO control to 4:1.
Attack Control
The ATTACK control sets the time it takes the Compressor/Limiter to respond to increases in signal level (by reducing gain). You can use this control to shape the "front end" of the dynamics envelope. For example, a short attack makes a snare sound "thin," while longer attacks emphasize the thump. Fast attacks can lead to "pumping" if gain reduction is too aggressive. Using the LOW CUT filter can help mitigate overreaction to plosive sounds.
Release Control
The RELEASE control sets the time the Compressor/Limiter takes to increase the gain after the input level drops. Longer settings preserve input signal dynamics, while shorter settings reduce them, potentially increasing apparent reverberation and causing "breathing" artifacts at extreme gain reduction.
Compressor Output Control
This control adjusts the output level of the compressor section, offering gain recovery from 10dB to full muting, provided to the COMP output jack.
Gain Reduction LED Meter
The GAIN REDUCTION meter displays the compressor's attenuation action, offering a wide range and high resolution.
Semi-Parametric EQ
The ART Pro Channel II™ offers a four-band semi-parametric equalizer. The entire EQ can be bypassed with a single switch. Each band has +12dB of control range. The High and Low EQ bands are shelving type with switch-selectable turnover points. The two Mid bands are continuously tunable over a three-octave range, with an additional three octaves available via a range switch. Filter "Q" can be adjusted to be narrow or wide via separate switches.
EQ Bypass Switch
This switch allows you to instantly set the EQ completely flat without losing the current EQ settings.
CLIP LED
This LED indicates clipping in any section of the Pro Channel II™. Clipping can be isolated by reducing the Preamp output (if the LED remains lit) or the Compressor output (if the LED goes out, indicating clipping in the compressor or EQ).
Rear Panel Connections
Master Output Control
The OUTPUT LEVEL control provides gain or attenuation to adjust for a variety of system operating levels. This control affects the levels sent to the A/D converter and to the balanced analog OUTPUT jacks.
Output Meters
The ART Pro Channel II™ provides both analog VU and LED level meters. The analog VU meter displays signal level relative to processor settings, with "0" VU corresponding to +4dBu on the balanced output. The upper LED bargraph indicates tube warmth, with the final LEDs marked "Clip" for preamp gain that is too high.
VU Meter Switches
These switches allow monitoring of levels at the Preamp output, Compressor output, EQ section, or Main output. With both switches out (POST/MAIN), the meter shows the final output level. With the PRE switch engaged, it monitors the EQ section output. The second switch allows selection of levels before or after the compressor (Post for COMP OUT, PRE for Preamp Out).
INPUT Jack
This XLR jack provides balanced inputs to the microphone preamplifier. The input impedance of the XLR connection is variable via the front panel Impedance knob. The front panel 1/4" Instrument input overrides the rear jack when used.
PREAMP OUT Jack
This 1/4" T/S unbalanced jack provides a direct signal from the microphone preamplifier, ahead of the EQ and dynamics processors. This output can be used with the INSERT INPUT jack to insert external signal processors between the main preamp section and the compressor.
COMP IN Jack
This 1/4" T/S unbalanced jack is an input to the EQ and dynamics processing sections. It can be used with the MIC PREAMP OUTPUT jack to insert external signal processors between the main preamp section and the EQ and dynamics processing.
COMP OUT Jack
This 1/4" T/S unbalanced jack provides a direct signal from the microphone preamplifier, ahead of the EQ and dynamics processors. This output can be used with the INSERT INPUT jack to insert external signal processors between the main preamp section and the EQ and dynamics processing.
EQ IN Jack
This 1/4" T/S unbalanced jack is an input to the EQ and dynamics processing sections. It can be used with the MIC PREAMP OUTPUT jack to insert external signal processors between the main preamp section and the EQ and dynamics processing.
OUTPUT Jacks
The analog output of the Pro Channel II™ is available on both a 1/4" TRS balanced jack and an XLR jack. This output is active balanced and adjusts to balanced or unbalanced termination without gain change.
OUTPUT LEVEL Switch
This switch optimizes the output level of the Pro Channel II™ based on the connected equipment. In the out position, the balanced output is -10dBV (approx. 0.3V RMS), suitable for semi-pro or consumer gear. When depressed, the XLR output is +4dBu (approx. 1.2V RMS) at "0" VU, for professional line-level gear.
Applications
Bypassing Components
To bypass the vacuum tube microphone preamp: Use the preamp INSERT INPUT jack instead of the Instrument or Mic input jack.
To bypass the Compressor/Limiter: Use the COMP bypass switch.
To bypass the EQ: Use the EQ bypass switch.
Optimizing The Preamp For Lowest Noise
The ART Pro Channel II™ preamp can be optimized for low noise by combining the PAD and Input GAIN controls for mic and line level signals. Note: The PAD control does not affect the INSTRUMENT INPUT.
- Bypass the Compressor/Limiter, Expander/Gate, and EQ. Center the OUTPUT LEVEL control to "0" dB gain. Use the OUTPUT LEVEL LED meter to monitor the input stage clip level.
- Start with the PAD in the "OUT" position and the GAIN control centered. Observe the OUTPUT LEVEL LED meter's peak-hold function. Ensure the red LED does not indicate clipping after a transient; the peak-hold indicator should be in the "yellow" range or within -5dB of levels.
- If the signal level is too high, engage the PAD switch.
- Adjust the GAIN control to keep peak levels within the -5dB range of the OUTPUT LEVEL LED meter.
Warranty Information
Limited Warranty
Applied Research and Technology (ART) warrants this product and its components to be free from defects in workmanship and materials for three years from the date of purchase. ART will repair or replace, at its option, defective products or parts upon prepaid delivery to the factory service department or an authorized service center, accompanied by proof of purchase.
Exclusions
This warranty does not cover misuse, abuse, unauthorized alterations, or repairs. It is void if the serial number is altered, defaced, or removed. ART reserves the right to make design changes or improvements without obligation to apply them to previously manufactured products. ART is not liable for consequential damages, including loss of use. Some states may not allow limitations on incidental or consequential damages, so these limitations may not apply. This warranty grants specific rights, and other rights may vary by state.
For units purchased outside the United States, service will be provided by an authorized ART distributor.
Service
For service, use the following procedure for units within the United States. For international service, contact your authorized ART distributor.
- Verify the unit is the cause of the problem. Ensure proper power, correct cable connections, and functional cables.
- If the unit is at fault, document the problem, including how and when it occurs.
- Contact Customer Service via the website at http://www.artproaudio.com, navigate to the "Resources" page, and complete the "Return Authorization Request" form. Your report will be submitted for evaluation.
- ART will contact you with an RA number, shipping address, and instructions after processing your request.
- Pack the unit in its original carton or a suitable substitute. Do not use the original carton as a shipping carton; place it inside another box. Print the RA number clearly under the address.
- Include with the unit: a return shipping address (no P.O. Boxes), a copy of the purchase receipt, a daytime phone number, and a description of the problem.
- Ship the unit via your chosen carrier or delivery service.
For your reference:
Date of purchase: _______________ Purchased from: _______________ Serial number: _______________
Specifications
Input Impedance
- Mic: 150 to 3.4K Ohms, variable
- Instrument: 2.5M Ohms
- Preamp Insert: 7.5K Ohms
Output Impedance
- Balanced Output: 600 Ohms balanced
- Unbalanced Output: 300 Ohms
- Insert Outputs: 300 Ohms
Frequency Response
- Analog In to Analog Out: 12 Hz to 100 KHz +0, -1 dB
THD
- 1 KHz: < .015% typical
- 20 to 20 KHz: < .033% typical
Equivalent Input Noise
- Mic/Line: -128 dBu, Input shorted, Max gain, "A" weighted
- Instrument: -109 dBu, Input shorted, Max gain, "A" weighted
Maximum Input Level
- Mic: +18 dBu balanced
- Instrument: +15 dBu
Maximum Gain
- Mic: 70 dB (XLR to balanced output)
- Instrument: 64 dB (1/4" to balanced output)
Maximum Output level
- Balanced: +24 dBu
- Unbalanced: +20 dBu
- Output Level At Meter 0 VU: +4 dBu/-10dBV
Preamp
- Microphone Gain: 0 dB to +56 dB
- Instrument Gain: +3 dB to +50 dB
- Low Cut Filter: 10 - 250 Hz, 1-pole, 6 dB/Octave
EQ
- Boost/Cut: +12 dB on each band
- Low Freq. Tuning: 40 / 120 Hz Selectable
- MID 1 Freq. Tuning: 20 Hz to 2 KHz continuously variable
- MID 2 Freq. Tuning: 200 Hz to 20 KHz continuously variable
- High Freq. Tuning: 6 KHz / 18 KHz Selectable
Compressor/Limiter
- Attack Time: 250 uSec. to 100 mSec.
- Release Time: 100 mSec to 3 Sec.
- Compression Ratio: 2:1 to 30:1
Dimensions
- 3.50" H x 19.0" W x 9.17" D
Weight
- 11 lbs.
Power Requirements
- USA – 105 to 125 VAC/ 60 Hz Export units configured for country of destination.
Note: 0 dBu = 0.775 VRMS, 0 dBV = 1 VRMS. ART maintains a policy of constant product improvement. ART reserves the right to make changes in design, or make additions to, or improvements upon, this product without any obligation to install same on products previously manufactured. Therefore, specifications are subject to change without notice.
Notes
Blank page for notes.
