Pro Channel TUBE MIC PREAMP / COMPRESSOR / EQUALIZER USER’S GUIDE
Contents FEATURES......................................................................... 5 OVERVIEW ........................................................................ 6 WHY USE AN EXTERNAL PROCESSING CHANNEL? ...............................6 DESIGN NOTES..................................................................................6 SETTING UP ...................................................................... 7 UNPACKING ........................................................................
CLIP INDICATOR .............................................................................. 13 EQUALIZER CIRCUIT ........................................................................ 13 Low Control ........................................................................................... 13 Low Switch ............................................................................................ 13 Lo-Mid Control .......................................................................................
GROUNDING ....................................................................................21 TUBE REPLACEMENT ..................................................... 21 WE’RE ON-LINE! .............................................................. 22 WARRANTY AND SERVICE INFORMATION .................... 22 LIMITED WARRANTY ........................................................................22 SERVICE .........................................................................................
Features The Pro Channel is a unique product. It contains three independent, award-winning circuit designs: one of the finest tube microphone preamplifiers available, one of the finest optical tube compressors available, and one of the most flexible EQs you’ve ever used.
Overview Why use an external processing channel? The best way to get a signal to tape is by using the shortest signal path. In most cases, the shortest path is as follows: mic to preamp to compressor to EQ to tape. (The signal doesn’t even go through a mixer!) This isn’t a new concept, but it has become more relevant with the availability of affordable mixing consoles. As their name implies, most affordable mixers are optimized for signal routing and general level mixing.
The compression circuit features a VCA-less design and utilizes either optical (Vactrol®) or tube, dual triode electronics for superior musical performance. The compressor is soft knee by design. Although it is capable of providing a thoroughly “squashed” signal, it was designed to excel in areas where transparent and musical dynamics control is desired. The beauty of the optical design is its ability to apply heavy amounts of compression without pumping and breathing like VCA-based compressors.
Installation The Pro Channel may be employed in a number of setups, including: • between a microphone and a digital recorder, mixer, or analog recorder; • in a mixer’s channel insert points; • between a microphone and signal processors; and • between electronic musical instruments (synthesizers, guitars, basses, samplers, acoustic instruments with pickups, etc.) and other gear. Safety Precautions WARNING: To avoid the risk of shock or fire, do not expose this unit to moisture.
Front Panel Controls and Indicators Preamp Circuit Gain Control The Gain control sets the Pro Channel’s input gain. Turn the control clockwise to increase gain and counter-clockwise to decrease it. The front panel calibrations (-11dB to +30 dB) refer to the Gain Switch (see next section) in the “Norm” position with the input routed to the ¼” unbalanced input jack. Using the XLR (balanced) input connection results in 12dB more gain, thus making the control range from +1dB to +42dB.
before disconnecting microphones. Another Note: Most dynamic microphones won’t be affected or damaged if they are plugged into the Pro Channel when phantom power is turned on (we haven’t run across any). However, if the mic doesn’t need it, don’t use it. Some things are best left untested! Phase Switch The Phase switch is used to reverse the phase of the signal leaving the Pro Channel’s preamp section.
+10dB of gain (when turned fully clockwise). When setting up the preamp, start with the Preamp Output at its “0” position. Once you get the Gain control set the way you want it to sound, use the Preamp Output control to set the level out of the preamp (much like using the master volume control on a guitar amplifier). Use the Preamp Output control to recover gain when you have the Gain control set low for a “clean” sound.
Attack Switch The Attack switch selects the attack characteristics of both the tube and optical compressor circuits. The Fast position (in) allows the compressor to react quickly to fast-rising attacks. Note that the tube circuit has an inherently fast response and can be aggressive on signals with quick transients, such as snare drums. The Slow position (out) can be helpful in reducing compression artifacts for signals with very little high frequency content, such as piano or flute.
clockwise increases the level to a maximum of +20dB of gain. While you can use the compressor to add gain to a signal, it is better to add gain before the compressor for the best signal to noise ratio. If you want to use the compressor to add more gain, use the VU meter to monitor the Pro Channel’s output level, or use the meter on your recorder or mixer to make sure you won’t clip the next piece of equipment in the chain.
“weight” or “beef” to a week vocal and cutting it can “thin out” a signal that takes up too much room in the low end. Lo-Mid Control The Lo-Mid control is a dual concentric pot (i.e., there are two controls – one outer and one inner). The outer control is used to select a frequency while the inner one is used to apply boost or cut. The amount of boost or cut available depends on the setting of the Lo-Mid (Wide/Narrow) switch: ±12dB for Wide and ±20dB for Narrow.
“surgical” cutting of a frequency band without affecting adjacent frequencies too much. High Control The High control adjusts a shelving filter with a selectable corner frequency of either 6KHz or 18KHz. The two frequencies are selected with the High switch (see below). The high shelving filter affects all frequencies above the corner frequency when applying boost or cut. In other words, cutting at 6KHz also cuts 7KHz, 8KHz, etc. The High Frequency control has as range of ±12dB.
Master Controls Master Output Control The Master Output control sets the final output level leaving the Pro Channel. When the control is fully counterclockwise, there is no output. Turning the control clockwise increases the output level to a maximum gain of +10dB. When setting this control, refer to the VU Meter (set for the “Output” option—see below) or the level meter on your recorder or mixer.
Rear Panel Connections Input and Output Connections The Pro Channel’s XLR connectors follow the AES standard: Pin 1 = Ground, Pin 2 = Hot (+), and Pin 3 = Cold (-). The unbalanced ¼” phone jacks are the typical Tip = Hot (+) and Sleeve = Ground. Note: None of the Pro Channel’s circuitry is connected directly to the metal chassis. Either the input or output ground must be connected to another portion of the signal path in order to establish a ground reference.
The loops may also be utilized to “re-patch” the compressor and equalizer circuits in a different order (i.e., signal flow = preamp to equalizer to compressor). For information on how to do this, see Loop Connection Examples, below. Preamp - Compressor Loop A loop is provided between the preamp’s output and the compressor’s input. The Preamp Out (Send) jack takes its signal after the Preamp Output control.
Applications The Pro Channel’s main application is as a processing channel for a microphone, instrument, or line level source. To use the Pro Channel as a mic or line preamplifier only, simply press the Bypass switches to bypass the compression and equalizer circuitry. Plug a microphone directly into either input and set the Input and Output controls to provide an appropriate level into the next stage of your system. The Pro Channel is ideal for use as a DI box.
What is the best way to use EQ? There are two schools of thought on EQ: 1) Use as much as you need to make things sound good. 2) Don’t use any EQ. Most people follow the suggestion of “if it sounds good, it is good.” You need to use your ears and judge for yourself as their are no steadfast rules for EQ’ing. Here are a few pointers to guide you: • Always tweak the instrument you are EQ’ing while listening to it in the mix.
Special Effects For industrial, metal, or just “flavor” textures, experiment with the Pro Channel. Overdriving the preamp, compressor, and equalizer circuitry can add interesting textures when blended with vocals and other instruments. Purposely placing signals out of phase can also yield interesting results. No harm will come to the Pro Channel with this type of experimentation. However, be sure to have output and monitoring levels turned DOWN before “testing” the sound.
We’re on-line! For Product information, questions, applications, tips, answers and general discussion with ART employees, look for ART on the Internet. Email us at support@artproaudio.com and check out our Web Site at www.artproaudio.com. Warranty and Service Information Limited Warranty Applied Research and Technology(A R T) will provide warranty service for this unit in accordance with the following warranty statement.
2) If you believe the ART unit is at fault, go to www.artproaudio.com. You may contact Customer Service for more assistance, or directly request a Return Authorization for service in the “resources” area of the website. 3) If you are returning the unit for service, pack the unit in its original carton or a reasonable substitute. The original packaging may not be suitable as a shipping carton, so consider putting the packaged unit in another box for shipping.
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A R T Pro Channel Specifications Dimensions Weight Maximum Gain Dynamic Range Frequency Response Low-Cut Filter Input/Output Connections Insert Connections Input Impedance Output Impedance Maximum Input Level Maximum Output Level Equivalent Input Noise Phantom Power Compression Ratio Attack Time Release Time Maximum Compression EQ Frequency Bands Low Shelf Low-Mid Sweepable Low-Mid Q High-Mid Sweepable High-Mid Q High Shelf Boost/Cut per Band 6.5"D x 19"W x 3.50"H 12.0 lbs.
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