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, alerts you to the presence of uninsulated dangerous voltage inside the enclosure. Voltage that may be sufficient to constitute a risk of shock. This symbol, wherever it appears, alerts you to important operating and maintenance instructions in the accompanying literature. Please read manual. Read instructions: Retain these safety and operating instructions for future reference.
Pro Channel II™ Tube Preamp - Opto compressor - EQ IMPORTANT SAFETY INSTRUCTIONS – READ FIRST .......................................................................... 2 INTRODUCTION .................................................................................................................................... 4 INSTALLATION ..................................................................................................................................... 4 AC Power Hookup ..........................
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.
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.
Tube Voltage Switch The vacuum tube preamp section can be adjusted to run at two different plate voltages. Refer to Figure 1 for the location of the switch. Choose the “NORMAL” setting for adding warmth to the input signal. This setting has an increased amount of 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.
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. One example is to listen to a snare hit and adjust the attack control. A short attack makes the snare sound “thin”. As the attacks go longer (and the knob is turned clockwise) you should hear more of the thump in the compressed snare.
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 a switch selectable turnover point. The two Mid bands can be continuously tuned over a three octave range, plus a range switch adds another three octave range. You can adjust the filter "Q" to be either narrow or wide via separate switches.
FIGURE 4 – Signal Flow Block Diagram 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 the signal level various points of the processor depending on the setting of the VU Meter Switches.
FIGURE 5 – Output Section 11
REAR PANEL CONNECTIONS FIGURE 6 - Rear Jacks INPUT Jack This XLR jack provides balanced inputs to the microphone preamplifier. The input impedance of the XLR connection is variable by the front panel Impedance knob. The Front panel 1/4" Instrument input overrides the rear jack when it is 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.
EQ IN Jack This 1/4” T/S unbalanced jack is an input to the EQ and dynamics processing sections. This input can be used in conjunction with the MIC PREAMP OUTPUT jack to insert external signal processors between the main preamp section and the EQ and dynamics processing of the Pro Channel II™. OUTPUT Jacks The analog output of the Pro Channel II™ is available on both a 1/4” TRS balanced jack and an XLR jack.
APPLICATIONS Bypassing Components Of The Pro Channel II™ 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 preamp of the ART Pro Channel II™ can be optimized for low noise by combining use of the PAD and Input GAIN control for mic and line level signals.
WARRANTY INFORMATION Limited Warranty: Applied Research and Technology will provide warranty and service for this unit in accordance with the following warrants: Applied Research and Technology, (A R T) warrants to the original purchaser that this product and the components thereof will be free from defects in workmanship and materials for a period of three years from the date of purchase.
SERVICE The following information is provided in the unlikely event that your unit requires service. Use this procedure to return units in the United States only. For service outside the United States, please contact your authorized A R T distributor. 1) Be sure that the unit is the cause of the problem. Check to make sure the unit has the proper power supplied, all cables are connected correctly, and the cables themselves are in working condition.
SPECIFICATIONS Input Impedance Mic ........................................................................................................ 150 to 3.4K Ohms, variable Instrument ............................................................................................. 2.5M Ohms Preamp Insert ........................................................................................ 7.5K Ohms Output Impedance Balanced Output..................................................................................
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