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Solution Delivery Series
204
aural exciter and big bottom
optical
Instruction Manual
P/N 999-4140 Revision 2 Released 09/01/2001 Manufactured by
Aphex Systems Ltd.
11068 Randall St. Sun Valley, CA 91352 USA
S Y S T E M S
Copyright 2001 Aphex Systems Ltd. All rights reserved.
Produced by: Donn Werrbach. Creation tool: Adobe InDesign 1.5. Printed by: Stuart F. Cooper Co., Los Angeles.
204
instruction Manual
Safety Declarations
CAUTION: For continued protection against risk of fire, replace only with the same type and rating of fuse. ATTENTION: pour une protection continue contre les risques d'incendie, ne remplacer qu'avec la même valeur et même type de fusible. WARNING: This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the operating guide, may cause interference to radio communications. Operation of this equipment in a residential area is likely to cause interference in which case the user will be required to correct the interference at his own expense. The user is cautioned that changes and modifications made to the equipment without approval of the manufacturer could void the user's authority to operate this equipment. It is suggested that the user use only shielded and grounded cables to ensure compliance with FCC Rules.
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®
C 59887
US
Conforms to standards UL60950 and EN60950.
Aphex Systems Ltd. Model 204
Aural Exci er and OPTI t CAL Bi Bottom g
204
A MESSAGE FROM THE PRESIDENT Dear Aphex Customer, We are very pleased to have been able to create the Model 204's unique, powerful processing and deliver it to you in such a cost effective package. Years of research and development, as well as over 20 years of direct experience in the recording, broadcast and PA fields produced the latest refinements of the Aural Exciter and the development of Optical Big Bottom. There are other devices on the market which claim to do the same things as the Model 204 but the comprehensive patent protection on our technology simply makes those claims unrealizable. The truth is clearly evident every time a proper comparison is made. We are happy that you have made the right choice and we are sure that you will be happy with that choice for many years to come.
Marvin Caesar
Copyright 2001 by Aphex Systems, LTD. All rights reserved. All Aphex products are trademarks or registered trademarks of Aphex Systems, LTD. Other brand and product names are trademarks or registered trademarks of their respective holders.
Aphex Systems Ltd. Model 204
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instruction Manual
ATTENTION
This instruction manual is intended to be a complete reference on the Model 204. We encourage you to read it! If you don't, at least peruse the Table of Contents to familiarize yourself with the scope of information available to you. We want you to get the fullest measure of satisfaction from your new Model 204. To that end, this manual was written to anticipate most of the questions and problems users are likely to encounter. Please let the manual serve as your guide and mentor. You may find its various sections on wiring and connecting especially helpful.
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Aphex Systems Ltd. Model 204
Aural Exci er and OPTI t CAL Bi Bottom g
Table of Contents
1.0 QUICK START With Big Bottom 1.1 Simple Hook-up and Settings ............................................................................................. 6 2.0 INTRODUCTION 2.1 The Aural Exciter Legacy ...................................................................................................... 8 2.2 The Aural Exciter and Big Bottom Technologies Explained .................................................... 8 2.3 Unpacking and Inspecting ................................................................................................... 9 2.4 Simplified Block Diagram ..................................................................................................... 10 3.0 INSTALLATION AND INTERFACING 3.1 Installation .......................................................................................................................... 3.2 Rear Panel View ................................................................................................................... 3.3 AC Line Connection ............................................................................................................. 3.4 Input Connectors ................................................................................................................ 3.5 Output Connections ............................................................................................................ 3.6 Nominal Operating Level Selector Switch ............................................................................. 3.7 Wiring Diagrams .................................................................................................................. 4.0 CONTROLS AND INDICATORS 4.1 Front Panel View .................................................................................................................. 4.2 Big Bottom Tune Control ....................................................................................................... 4.3 Big Bottom Drive Control & Indicator .................................................................................... 4.4 Big Bottom Mix Control ......................................................................................................... 4.5 Aural Exciter Tune Control .................................................................................................... 4.6 Aural Exciter Harmonics Control ............................................................................................ 4.7 Aural Exciter Mix Control ....................................................................................................... 4.8 Process IN/OUT Buttons ......................................................................................................... 5.0 OPERATION AND APPLICATIONS 5.1 In-Line Patches ..................................................................................................................... 5.2 Console Insert Patches ......................................................................................................... 5.3 Effects Loop Patches ............................................................................................................ 5.4 Optimizing Aural Exciter Effects ............................................................................................ 5.5 Optimizing Big Bottom Effects .............................................................................................. 5.6 Recording: Tracking and Mixing ........................................................................................... 5.7 Live Concerts and Sound Reinforcement .............................................................................. 5.8 Stage Monitors ................................................................................................................... 5.9 Guitar, Bass and Keyboard Rigs ............................................................................................ 5.10 Nightclubs and Discos ........................................................................................................ 5.11 Karaoke and Stereo Systems ............................................................................................... 5.12 Tape Duplicating ................................................................................................................ 11 11 11 11 11 11 12 13 13 13 13 14 14 14 14 15 15 16 17 18 18 19 20 20 21 21 22
204
6.0 WARRANTY AND SERVICE 6.1 Limited Warranty ................................................................................................................. 23 6.2 Service Information .............................................................................................................. 23 7.0 APPENDICES Appendix A - Introduction to Balanced and Unbalanced Wiring ................................................. Appendix B - Dealing With Ground and Hum ............................................................................ Appendix C - Wiring Techniques ................................................................................................. Appendix D - Back to BASS-ICS ................................................................................................... 24 31 27 32
8.0 SPECIFICATIONS 8.1 General Specifications .......................................................................................................... 34 8.2 Architectural Specifications .................................................................................................. 35 8.4 Patent Notice ........................................................................................................................ 36
Aphex Systems Ltd. Model 204
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1.0 Quick Start
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instruction Manual
1.1 SET UP To get started fast, first pay attention to unpacking and inspection covered in section 2.3. Then, follow the wiring diagram for an in-line application shown below. If you need to run the Model 204 with an insert patch instead, refer to section 5 for more information. Finally, refer to the control settings below to get your Model 204 sounding great. Don't neglect to later run through this manual, however, as there is a wealth of useful information here for you. Suggested Control Settings Start with the knobs pointing as shown. Then experiment with the different settings. When testing the effect of Big Bottom, turn off the Aural Exciter Mix. Likewise, turn off the Big Bottom Mix when testing the effects of the Aural Exciter. When you feel you have them both set up nicely, turn up both mixes and A/B with the IN/OUT buttons.
Recommended Starting Place Recommended Range Experimental Range
Indicator Legend
BIG BOTTOM DRIVE CONTROL & INDICATOR Turn clockwise until the green LED flashes brightly on bass peaks and fades out. This corresponds approximately to the amount of extra bass sustain you are creating. If the LED doesn't flash when you reach 2 o'clock, then check the Operating Level Switches.
BIG BOTTOM MIX CONTROL Adjusts the amount of bass enhancement being added into the original sound. The higher the setting the more dramatic the effect. Avoid using any more Mix than necessary or excessive peak levels will arise.
BIG BOTTOM TUNE CONTROL Sets the bass frequency range of the effect. Go clockwise to encompass higher bass frequencies, and counterclockwise to focus more on the lower bass sounds.
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Aphex Systems Ltd. Model 204
Aural Exci er and OPTI t CAL Bi Bottom g
204
Quick Start
In-Line Hookup to Rear Panel
From Outputs of Other Line Level Devices to 204's Inputs
Use balanced or unbalanced cables as needed. Consult section 7 for wiring options.
Select the correct OPERATING LEVEL to match your interconnecting equipment. Both the outputs and inputs are switched simultaneously.
From 204'S Outputs to Inputs of Line Level Devices
AURAL EXCITER TUNE CONTROL Adjusts the frequency range of the effect. Tune lower for more mid pickup and presence. Tune higher for an airier sound.
AURAL EXCITER MIX CONTROL Adjusts the amount of Aural Excitement being added into the original sound. The higher the setting the more dramatic the effect. Use just the amount needed to feel the effect. Excess Mix can be sound harsh.
PROCESS IN/OUT SWITCH Turns Aural Exciter and Big Bottom off and on simultaneously. Button glows green when on. Each channel is switched independently.
AURAL EXCITER HARMONICS CONTROL Sets the relative richness of harmonics created by the Aural Exciter. Use more for instrument tracks and less for voice tracks. What's best for mixes needs to be determined by experiment.
Aphex Systems Ltd. Model 204
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2.0 Introduction
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2.1 THE AURAL EXCITER LEGACY
instruction Manual
Congratulations, you have just purchased the latest in Aural Exciter technology, combined with the one and only Big Bottom circuit. Aphex Systems, Ltd. started doing business in 1975 with the introduction of the Aural Exciter, which has become a standard in the professional audio industry. In the past 26 years, the Aural Exciter has been used on an innumerable number of albums, CD's, movies, broadcast productions, commercials and concerts. Interestingly enough, the first Aural Exciter was only available on a rental basis for $30.00 per minute! It wasn't until 1981, when the Type 2 processor was developed, that recording studios, touring companies and broadcast studios were able to purchase it. The Aural Exciter has come a long way since then, though the basic principles of its operation are the same. After the Type 2 was well established in the professional realm, a simpler circuit was designed and placed in a low cost Type B unit in 1983, making the Aural Exciter available to DJ's and musicians for use in modest P.A. systems and project studios. Further refinements and even lower costs were realized with the introduction of the TYPE C in 1985. In 1989 a new professional unit, the TYPE 3, was developed which included all the circuit and control improvements learned up to that time. In 1992, the TYPE C2, offered yet further improvements on the basic Aural Exciter circuitry making it quieter, more musical, and easier to set up and use. It also featured the original Big Bottom, a patented circuit which revolutionizes processing of low frequencies. Now, the latest in this distinguished line is the Model 204 dual channel Aural Exciter and Optical Big Bottom. The 204 combines updated and improved circuitry with new attractive styling and full professional features at a very moderate price. The newly developed Optical Big Bottom circuit surpasses all other bass processors. It remains simple and easy to use. Aphex Systems is committed to providing high performance processors to the professional audio industry that are innovative and beyond the scope of similar products. The Aural Exciter and Big Bottom are patented in the United States, Japan and most of Europe. Others may claim they are doing the same thing, but they cannot. They simply have to resort to some form of EQ (amplitude correction or expansion), distortion generating, phase scrambling and/or filtering. They cannot add or restore detail, nor can they safely increase bass. They can only increase peak levels causing clipping, feedback, tape distortion and listener fatigue. 2.2 THE AURAL EXCITER AND BIG BOTTOM TECHNOLOGIES EXPLAINED The AURAL EXCITER is an audio processor that recreates and restores missing harmonics. Harmonics are musically and dynamically related to the original sound, revealing the fine differences between voices and various instruments. Reproduced sound is audibly different than the original live sound because of the loss in harmonic detail, often sounding dull and lifeless. The Aural Exciter adds harmonics, restoring the sounds natural brightness, clarity and presence, effectively improving detail and intelligibility. Using the Aural Exciter on specific instruments and/ or in the final mix brings life back to the recording. The original Aural Exciter patent disclosed a method for generating harmonics which was amplitude dependent. In nature, generally speaking, the higher the amplitude, the higher the amount of harmonics. There are instances, however, in which there are high level sinusoidal waveforms, which should not have harmonics added, and other instances which have low level transients, which could be enhanced by additional harmonPage 8 Aphex Systems Ltd. Model 204
Aural Exci er and OPTI t CAL Bi Bottom g
SIMPLIFIED SIDECHAIN DIAGRAM Input Original Signal SUM Sidechain Processing
204
Introduction
Output
ics. Our latest patent, the Transient Discriminate Harmonics Generator, recognizes transients (transient discriminate) over a wide dynamic range and generates harmonics on them. The result is a more predictable and natural sounding enhancement over a wider range of inputs. The Aural Exciter extends the high frequencies, unlike EQ's and other brightness enhancers which only boost the high frequencies and often alter the overall tonal balance. The stereo image is enhanced with the Aural Exciter, resulting in a greater perceived loudness without an introduction of noise into the audio path. The Aural Exciter is a single ended process, that can be inserted at any point within the audio chain. The input signal is split into two paths. One path goes to the output unmodified, while the other path, known as a sidechain, goes through the Aural Exciter circuit which is comprised of a tunable high pass filter and a harmonics generator. The Aural Exciter circuit applies frequency dependent phase shift and transient discriminate harmonics. The output of the Aural Exciter's harmonic circuit is mixed back with the unmodified signal but much lower in level. When used at nominal settings, the Aural Exciter circuit does not add significant level to the original signal. Even though the added information is low in level, the perception is a dramatic increase in mid and high frequencies. The Model 204 also incorporates another exclusive Aphex patent, Big Bottom, providing a stronger, more powerful bass, increased sustain and density without an increase in the peak output. While static bass-boost EQ's and subharmonic generators will increase the bass energy level, the resultant large boost in peak level often increases overload distortion. Big Bottom resembles the Aural Exciter in that a processed signal is mixed back into an unmodified signal to produce an enhanced output signal. The sidechain path goes through the Big Bottom circuitry, comprised of a variable low-pass filter and a phase and dynamics processor. Big Bottom circuitry dynamically contours the bass response of a complex range of shapes in the 20Hz to 120Hz range. Big Bottom increases the perception of low frequencies without significantly increasing the maximum peak output. The bass frequency response is dynamically optimized to isolate and enhance the lowest bass frequencies to provide a deeper and more resonant bass. 2.3 UNPACKING AND INSPECTING Your Aphex product was carefully inspected and packaged at the factory prior to shipment. The carton and its internal packing materials are designed to protect the unit from most rough handling than can occur during transport and handling. However, you should thoroughly inspect the carton and its contents for signs of physical damage before attempting to use this device. It is your responsibility to immediately report any damage to your dealer or the freight company so that a damage claim can be appropriately filed. Shipping claims are always the responsibility of the consignee (that's you). We also encourage you to save all of the original packing materials in the event that this unit should ever have to be returned to the dealer or factory for repair.
Aphex Systems Ltd. Model 204
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Introduction
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Page 10 Active Balanced Outputs +4/-10 Operating Level Switch XLR-3M SUM Tunable Highpass Filter Mix Tune 800Hz-6kHz Variable Harmonics Transient Discriminate Harmonics Generator 1/4" TRS Tunable Lowpass Filter Tune 50Hz-190Hz Phase & Dynamics Processor Mix Variable Drive
2.4 SIMPLIFIED BLOCK DIAGRAM
Active Balanced Inputs
XLR-3F
1/4" TRS
Aural Exciter Sidechain
Big Bottom Sidechain
instruction Manual
Aphex Systems Ltd. Model 204
Effects are created through dynamic phase, frequency, and amplitude modification and recombination.
Aural Exci er and OPTI t CAL Bi Bottom g
3.0 Installation & Interfacing
3.1 INSTALLATION The Model 204 occupies a single rack space (45mm or 1-3/4 inches) of a standard EIA equipment rack. When rack mounting, use appropriate cushioned rack screws. Never restrict air flow through the device's fan or vents. When installing the units into a rack, distribute the units evenly. Otherwise, hazardous conditions may be created by an uneven weight distribution. Connect the unit only to a properly rated supply circuit. Reliable earthing (grounding) of rack mounted equipment should be maintained. Try not to position the 204 directly above devices that generate excessive heat such as power amplifiers (unless adequately ventilated) or near equipment with heavy transformer hum fields. 3.2 REAR PANEL VIEW
OPERATING LEVEL -10 +4 OPERATING LEVEL -10 +4
204
SYS T E MS
SUN VALLEY, CA - MADE IN U.S.A.
APHEX, AURAL EXCITER, AND BIG BOTTOM ARE REGISTERED TRADEMARKS OF APHEX SYSTEMS LTD.
Pin1 = Sleeve = GND, Pin 2 = Tip = HI, Pin 3 = Ring = LO
Pin1 = Sleeve = GND, Pin 2 = Tip = HI, Pin 3 = Ring = LO
AURAL EXCITER with BIG BOTTOM
MODEL 204
59887
CONFORMS TO UL60950 AND EN60950
3.3 AC LINE CONNECTION Observe the label to the right of the fused receptacle indicating the nominal ac supply voltage that your 204 is built for. If your supply voltage does not agree with this rating, you will have to consult the factory or an authorized distributor or representative about changing the line voltage of your unit.
T
WARNING: The line voltage setting is not user convertible. 3.4 INPUT CONNECTORS The input connectors are located on the rear panel. There are two input connectors per channel, one 1/4" TRS phone type and one XLR-3F type. All inputs are fully balanced at all operating levels. Either of the input jacks can be used unbalanced whenever necessary (consult the wiring diagrams, next page). You can take advantage of the true balanced inputs by using a "pseudo-balanced" wiring scheme from any unbalanced outboard gear. Refer to Appendix A for more wiring information.
R
NOTE: Be aware that the TRS and XLR input jacks are wired directly together, and will severely load each other down if equipment is plugged into both inputs. Use only one or the other. 3.5 OUTPUT CONNECTORS The output connectors are located on the rear panel. There are two output connectors per channel, one 1/4" TRS phone type and one XLR-3M type. Refer to Appendix A for more information on the proper wiring of balanced and unbalanced lines. 3.6 OPERATING LEVEL SWITCH Between the input and output jacks are located the Operating Level switches. These switches set the nominal operating level for all of the input and output jacks simultaneously to either -10dBV or +4dBu. You should select the position that most closely matches your signal level. In the event that you are not familiar with the operating levels of the equipment in your system, you should consult the manuals for each device so that proper gain structures are maintained. Too high an output (+4dBu) connected to a device requiring lower input levels (-10dBV) can result in clipping of the input stage and generAphex Systems Ltd. Model 204 Page 11
Primary Power Ratings: 120 60Hz 0.065A Fuse = 250V/0.125A T
U.S. PATENTS 4,150,253 5,359,665 5,424,488 OTHER U.S. AND FOREIGN PATENTS ISSUED OR PENDING
OUTPUT
CHANNEL 2
INPUT
OUTPUT
CHANNEL 1
INPUT
Installation & Interfacing
ating distortion. In the reverse situation, connecting a -10dBV output to a +4dBu input will tend to increase the noise floor, thus degrading the systems signal-to-noise ratio. In general, most entry level "home studio" equipment operates at -10dBV as it is assumed that the user will likely intermix home hi-fi equipment, such as cassette decks and CD players. Most professional recording gear and live sound equipment operates at +4dBu. WIRING DIAGRAMS
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instruction Manual
Throughout this manual we use TS and TRS as abbreviations. Here is a complete definition: TS refers to the Tip-Sleeve or "mono" 2-conductor type and TRS refers to Tip-Ring-Sleeve or "stereo" 3 conductor type 1/4" phone connectors. This applies to jacks (female connectors) and plugs (male connectors).
R
Note: We recommend using only conventional 1/4" phone plugs with the Model 204. Professional patch bay cords using brass PJ055 telephone type plugs are designed to a different standard and will not make full contact with the Model 204 phone jacks. When it comes to wiring, one picture is worth a thousand words. The following illustrations show all the different ways you will probably ever need to hook up your equipment. You typically will have little trouble using professional manufactured cables, but you may wish to make your own. In case of hum, buzz, or noise troubles, check your cables against these diagrams for correctness. You may benefit from isolating the shield wire at the sending end (never the receiving end) if you experience hum using balanced cables.
Female XLR Mono Plug
UNBALANCED Cables
Mono Plug
Male XLR
Mono Plug
Mono Plug
Female XLR
Mono Plug
No Connect
BALANCED Cables
Stereo Plug Stereo Plug
Female XLR
Optional Ground Lift (Sending End Only) Stereo Plug No Connect Hum Kill Option Female XLR Male XLR Female XLR Male XLR
No Connect Hum Kill Option
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Aphex Systems Ltd. Model 204
Aural Exci er and OPTI t CAL Bi Bottom g
4.0 Controls & Indicators
4.1 FRONT PANEL VIEW
204
4.2 BIG BOTTOM TUNE CONTROL This control lets you optimize the bass enhancement frequency band. Where this is set depends upon your sound system and the type of music being played. Typically, 12:00 is a universal position. However, you may want to experiment with other settings. The range is from 50Hz to 190Hz. At center, you are tuned to about 110Hz.
4.3 BIG BOTTOM DRIVE CONTROL & INDICATOR This needs to be set at a point where the processor receives the optimum level required for Big Bottom to work effectively. To find the optimum level, turn the control clockwise until the green L.E.D. at the right of the Drive control pulses on the bass peaks. Longer and brighter pulsation means a longer bass sustain is being created. You will find a range of settings that yields very musical and powerful bass. If the green L.E.D. doesn't pulse by the time you reach 2 o'clock, check the Operating Level switches on the back panel and make sure they are set properly. It's possible that you have set the Operating Level switch to +4dBu and you have a -10dBV input. On the other hand, if the green L. E.D. is pulsing strongly at settings as low as 9 or 10 o'clock, you probably have a +4dBu input level with the operating level of the 204 switched to -10dBV. That can cause overload distortion. 4.3 BIG BOTTOM MIX CONTROL This control adjusts the amount of Big Bottom enhancement being added to the original signal. The lower the setting, the subtler the effect until there is no effect at all. The higher the setting, the more dramatic the effect. One of the benefits of the Big Bottom is that it can increase the bass power without greatly increasing the peak output level. That means that loudspeakers and amplifiers will not be overdriven even though the bass has been extended and increased in power. Extreme settings of the Big Bottom Mix control, however, will increase the peak output level significantly, so we recommend staying within some reasonable limits. Generally, the best results are found between the 9 and 2 o'clock settings. Try working the Big Bass Tune, Drive, and Mix controls when maximizing the bass enhancement.
Aphex Systems Ltd. Model 204
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204
Controls & Indicators
4.4 AURAL EXCITER TUNE CONTROL
instruction Manual
The Aural Exciter Tune control adjusts the corner frequency of the high pass filter, thus setting the range of frequencies being enhanced by the Aural Exciter. The range of the corner frequency is 800Hz (fully counter clockwise) and 6kHz (fully clockwise). The 12 o'clock setting is approximately 3kHz. As the tune control is adjusted clockwise, less and less midfrequency enhancement will take place. Refer to the Tune Control With Frequency Markings in section 5.4.
4.5 AURAL EXCITER HARMONICS CONTROL This control adjusts the amount of harmonics being generated by the exciter. It controls the texture and detail of the effect. The MIN position is generally considered NORMAL, and is useful for voices and total mixes. The MAX position is most useful on specific tracks, especially percussive instruments, horns, guitars and digital instruments. The higher settings provide more of an "edge" to a track or instrument and can sometimes make all the difference between just an OK track or one that really cooks.
4.6 AURAL EXCITER MIX CONTROL This control varies the amount of enhancement mixed back into the original signal, from the sidechain. Maximum effect is achieved when the control is set fully clockwise. No effect is audible when the control is turned completely counter clockwise.
4.7 PROCESS IN/OUT BUTTONS These lighted Process In/Out buttons allow you to turn the enhancement for each channel on and off individually. The IN position turns all processing on and sends Aural Exciter and Big Bottom enhancement to the outputs. The buttons glow green when processing is on. They are dark when processing is off. When processing is off, only the unmodified signal passes through to the outputs. Switching the button back and forth offers a quick A/B comparison, allowing you to hear the enhancements from the 204 in your program content. Note: This is not a hard wired bypass. The audio still passes through the input and output stages but enhancement sidechains are turned off.
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Aphex Systems Ltd. Model 204
Aural Exci er and OPTI t CAL Bi Bottom g
5.0 Operation & Applications
5.1 IN-LINE PATCHES The Model 204 has two independent channels. Each channel contains one Big Bottom circuit and one Aural Exciter circuit. Each channel may be used on completely different input signals. When the 204 is used on a stereo mix, match the settings of the controls on each channel. The Model 204 is typically used as an in-line device, see illustration below. USING A 204 IN AN IN-LINE CONFIGURATION
Ch1 Source Device (Line Level) Ch2 Ch1
204
2 4 0
Ch2
Destination Device (Line Level)
5.2 CONSOLE INSERT PATCHES The Model 204 can also be hooked-up (in-line) through a mixing console's Input Channel Inserts or Buss Inserts in one of two ways, as seen in the following two diagrams. One of the two types of hook-ups will be specified by the console manufacturer. USING A CONSOLE'S INSERT WITH SEPARATE JACKS
Ch1 Input Send Console Ch1 Output Return Ch1 Input Ch1 Output Console Insert Jacks
2 4 0
The following example is a hook-up that has become very popular particularly among manufacturers of lower to mid priced consoles. The cable required for this hook-up is a special Insert Cable of the TRS type. USING A CONSOLE WITH A SINGLE (TRS) INSERT JACK
2 4 0
Insert Cables are more than ordinary "Y" cables. The single (TRS) side can accept a signal coming from two directions when placed in a specially designed Insert jack on a console. The "Y" section is hooked up into the Model 204 through the respective input and output jacks. See the detailed drawing of an Insert Cable on the next page. Aphex Systems Ltd. Model 204 Page 15
204
Operation & Applications
WIRING A TRS INSERT CABLE
instruction Manual
Tip
IN
Tip Sleeve
Sleeve Sleeve Tip
Ring (Return)
Ring
R
Note: Some manufacturers reverse the Tip and Sleeve connections, where the Tip is Return and the Sleeve is Send. This would mean that IN becomes OUT and OUT becomes IN when referring to the previous drawing. Be sure to check the owner's manual of your console. 5.3 EFFECTS LOOP PATCHES As we stated early on, the Model 204 was primarily designed as an in-line device. However, if you choose to use it in an effects loop, keep in mind that the signal being received back into the console is not pure effects. The return is a mix of effects and the original sound. Because of this we recommend that you put the Mix controls of both the Aural Exciter and the Big Bottom on the maximum setting (fully clockwise) when using the 204 in an Effects Loop. Because very little Aural Excitement goes a long way, it is possible to get very good results from this type of set-up. USING A 204 IN AN EFFECTS LOOP
Post Fader AUX Send
2 4 0
AUX Return
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Aphex Systems Ltd. Model 204
Console
204
OUT
Tip (Send)
Sleeve (Ground)
Console Insert Jack
Aural Exci er and OPTI t CAL Bi Bottom g
204
Operation & Applications
5.3 EFFECTS LOOP PATCHES (cont.) SEPARATING THE AURAL EXCITER & BIG BOTTOM EFFECTS The following illustrates how you can use Big Bottom and Aural Exciter separately on different effects sends. Let's assign Effects (or AUX) Send 1 to the Aural Exciter and Effects (or AUX) Send 2 to Big Bottom. Now turn the Aural Exciter MIX control all the way up (completely clockwise) and turn the Big Bottom Mix all the way off (fully counter clockwise) on channel I of the 204. To set channel 2 up for Big Bottom processing, turn the Big Bottom Mix control all the way up (fully clockwise) and the Aural Exciter MIX all the way off (counter clockwise).
CH1 IN
CH1 OUT
MAX
MIN
MIN CH2 IN
CH2 OUT
MAX
AUX1 AUX1 AUX2 Send Return Send
AUX2 Return
5.4 OPTIMIZING AURAL EXCITER EFFECTS There are two independent channels, each containing one Aural Exciter circuit. Each channel may be used on completely different signals. The front panel provides two identical sets of controls for two separate channels. The Tune control adjusts the corner frequency of the high pass filter and the Mix control varies the amount of Aural Exciter enhancement that is mixed with the unmodified signal.
Experiment with the Aural Exciter controls to hear how each one enhances the original audio signal: 1. Make sure the Process Switch is IN. 2. Put the Aural Exciter Mix control on maximum, fully clockwise, to make it easy to hear the effect as it changes. 3. Vary the Tune control and listen for the frequency range that's being enhanced. The Tune control can be used to enhance a particular instrument so it stands out in the mix. 4. Go between MIN and MAX Harmonics and listen for the change in harmonics being added to the original audio signal. 5. After your experimental tour, set the Mix control to taste. Keep in mind that a little Aural Exciter goes a long way.
After a while you'll get a sense of where you like your Tune setting when using the Aural Exciter on individual tracks. The following chart can be used as a guideline for finding specific frequencies of commonly used musical instruments and voices. Aphex Systems Ltd. Model 204 Page 17
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Operation & Applications
2.3K
instruction Manual
When the Aural Exciter is used on individual tracks it's best not to overprocess exactly the same range frequencies with the tune control during the final mix. If you already processed individual tracks with a 204 try starting the final mix with the Tune control turned fully clockwise which is approximately 6kHz You should get a spacious, three-dimensional mix with an open "airy" quality.
1.8K 1.1K 524 6.1K 3.4K 4.6K
AURAL EXCITER TUNE CONTROL FREQUENCY POINTS
5.5 OPTIMIZING BIG BOTTOM EFFECTS There are two independent channels, each containing one Big Bottom circuit. Each channel may be use on completely different signals. Two identical sets of controls are provided. The Drive control needs to be set at a point where the processor receives the optimum level required for Big Bottom to work effectively. The Mix control adjusts the amount of Big Bottom enhancement being added to the unmodified signal. The Tune control sets the frequency below which the bass enhancement effects are generated.
70 64 49 197 79 108 138
BIG BOTTOM TUNE CONTROL FREQUENCY POINTS
Next to the Drive control is a green L.E.D. indicator. When the Operating Level (+4/-10) switch on the rear panel is set correctly and the Drive control is properly set up for nominal processing, this L.E.D. will illuminate brightly on bass peaks.
BIG BOTTOM EXPERIMENTING 1. Make sure the Process Switch is IN. 2. Set the Tune and Mix controls to 12:00. 3. Vary the Drive control and listen to how the bass can be made to hang over, or sustain, longer. Start by adjusting the Drive control until the green L.E.D. just flashes on bass peaks, then advance the Drive incrementally. 4. Vary the Mix control and listen for how subtle or dramatic you can make the effect. 5. Vary the Tune control to find what point gives you the most powerful or most pleasing effect.
5.6 RECORDING: TRACKING AND MIXING The Aural Exciter restores presence and clarity, improving transient response of individual tracks or whole mixes. Increased harmonic detail enables specific instruments to stand out in the mix, offering a more "live" or spacious sound. Imaging is improved with an open "airy" quality. Any instrument, such as a guitar, processed through the Aural Exciter circuit will have greater penetration, crispness and clarity. Specific instruments pop out in the mix, giving the instrument its own sonic identity without raising the volume of the instrument in the mix.
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Aphex Systems Ltd. Model 204
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Operation & Applications
Using Big Bottom on bass instruments tightens the sound, allowing individual notes to be more articulated and recognizable. Big Bottom provides more feeling, resembling a "live" sound. In the recording studio, post production suite or similar environment, post processing of previously recorded sound tracks can restore lost vibrancy and realism, even to the extent of saving dialog or sound effects which were thought to be unusable. Instruments and vocals can be made to stand out in the mix without substantially increasing the mix levels or using equalization. The Aural Exciter is especially useful in creating the perception of high frequencies and greater dynamics with pre-processing, bringing more presence and clarity to the final product. The Model 204 should be hooked up between a compressor like the Aphex 208 Easyrider Automatic Compressor and any equalization. Use the Aural Exciter in place of equalization whenever possible, as shown below.
Optional Compressor
2 4 0
DAT or Other Recorder
5.7 LIVE CONCERTS & SOUND REINFORCEMENT The Aural Exciter adds intelligibility without increasing levels, even with speaker systems that have reduced bandwidth. It does this through higher harmonics generation which improves vocal articulation through a sound system. Audio that is processed by the Aural Exciter will more easily penetrate noisy and reverberant environments by adding brightness and clarity through the addition of harmonics rather than increasing gain of frequency fundamentals which may lead to feedback. Any voice or instrument individually processed with the Aural Exciter circuit will have greater crispness and clarity allowing them to pop out in the mix with its own sonic identity. Big Bottom inexpensively increases the bass capacity of any sound system. It is as though you've added subwoofers to the system. If you already have subwoofers you'll think the number of subs in the system was increased. Equalizers are commonly used for tone control, elimination of feedback, and compensation for both system and room deficiencies. In some cases the Aural Exciter can replace certain functions of outboard equalizers because of the uniqueness of the Aural Exciter process. The Model 204 can be placed before or after the equalizer in the audio chain, depending on how you want to use the Model 204 in conjunction with equalization. For room equalization, we recommend placing the Model 204 before the equalizer, as shown in the illustration below. For recording and other applications, we recommend equalizing first, followed by the Aural Exciter.
Optional Compressor
2 4 0
System EQ
To Electronic Crossover, Amplifiers, and Speakers
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Operation & Applications
instruction Manual
If you use a compressor for smoothing out dynamics it should go into the audio chain before the Model 204. If you are using a limiter for system protection it should be the last thing in the audio chain before amplification. Note: The previous illustration depicts an in-line audio path. Most mixing consoles offer Master Bus Inserts for processing. 5.8 STAGE MONITORS Stage monitors are a necessity for performers but can be a source of problems for the sound engineer. For instance, in rock concert settings the existing high levels on stage are fighting the effectiveness of the stage monitors. The most common example is when the lead singer yells at you to give him more level in his monitors because he can't hear himself over the wall of guitar amplifiers. The volume that is required from the stage monitors is high enough that you're usually on the edge of feedback. Another situation is acoustic music performances such as folk or bluegrass. In this instance there is no problem with a high stage level. However, you have instruments that by nature have a low acoustical output that require high amounts of gain to reproduce them through PA and stage monitor systems. In this situation, you're typically on the edge of feedback especially as the number of mics increase. In both of these examples your are trying to get more gain out of the stage monitors than the limiting factor of feedback will allow. The Aural Exciter will give you a perceived increase in volume without putting your system into feedback. Put an Aural Exciter in line when the system is stable yet close to the point of feedback. The Aural Exciter may be the most viable option under these conditions. There are two types of monitor systems in use. The simplest and least expensive method is a foldback monitor system. Only one console is used for mixing both the "front of house" P.A. and the stage monitors. To use a Model 204 in a foldback monitor system, patch directly into the 204 from the line level monitor output on the console. The Model 204 should always come before equalization and then on to the amplifier and speakers. The other method is known as on-stage monitor mixing. In this scenario, a separate mixing console is placed on stage to mix the stage monitors. This is prevalent in larger, more sophisticated performance settings where there is typically many monitor mixes. Since we are dealing with a separate console, in most cases you'll have a choice of using a buss insert or patching "in-line". Refer to section 5.1 and 5.2 for patching instructions. 5.9 GUITAR, BASS & KEYBOARD RIGS The sampling rates of digital devices such as synthesizers, drum machines, samplers etc. limit the instruments bandwidth and resolution. They have no high end beyond a fixed point and can sound lifeless. Use of the Aural Exciter dramatically improves their overall sound by creating additional overtones, literally doubling the bandwidth. Any instrument, such as a guitar, processed through the Aural Exciter circuit gives the instrument its own sonic identity without raising the volume of the instrument in the mix. Musicians can include the 204 into their instrument rigs and process the sound they want before it reaches the sound mixer.
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Operation & Applications
5.10 NIGHTCLUBS AND DISCOS The Model 204 is great for smaller sound systems with a limited dynamic range and frequency response. You'll be surprised how much more bottom end you'll have without adding more speakers and amplifiers. No matter how good the sound system is, adding the Model 204 will improve clarity and intelligibility without increasing levels. Big Bottom inexpensively increases the bass capacity of any sound system. It is as though you've added subwoofers to the system. If you already have subwoofers you'll think the number of subs in the system was increased. It's also important to remember that when EQ's are introduced into the playback system they can cause ear fatigue and speaker damage. The overuse of EQ in nightclub and disco applications is commonplace. Use the Aural Exciter in place of an EQ in these applications and music seems louder and clearer, even at low levels, saving both your ears and speakers from harm. 5.11 KARAOKE & STEREO SYSTEMS The Model 204 is a perfect complement to Karaoke systems. In a small club situation, often the sound system and the microphones have a limited dynamic range and frequency response. Big Bottom will help tighten and increase bass. Aural Exciter helps overdubbed vocals become more intelligible and clearer in the mix. The 204 can give Karaoke performers that big "recording studio" sound that audiences want to hear. The two channels in most Karaoke and consumer grade equipment are marked left (L) and right (R), rather than one (1) and two (2). Regardless of these markings, the Model 204 can be used as a stereo component. Just make sure to match the settings of the controls on each channel for best results. You can replace outboard EQ's in home stereo systems with the Model 204. Big Bottom increases the "punch" of the bass and the Aural Exciter "pops" vocals, guitars and keyboards out front in the mix. USING A 204 WITH SEPARATE PREAMP AND AMPLIFIER
Ch1 Preamp Ch2 Ch1
2 4 0
Ch2
Amp
USING A 204 STEREO RECEIVER
Tape Monitor (Play) Stereo Tuner/ Amplifier Tape Out (Record)
2 4 0
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5.12 TAPE DUPLICATING
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Tape copies actually sound better and brighter than the original if they are first processed by the Aural Exciter. Moreover, there is no generation loss! Chances of tape saturation are minimized as there is little high end boost, which is common in other enhancers. The Model 204 may be used to "pre-process" recording to anticipate the audio degradation in the medium or during subsequent reproduction. Much of the detail added by the Model 204's Aural Exciter will survive filtering and distortion of the reproduction equipment, and provide a better quality audio playback. Bit-rate reduced (data compressed) digital audio tracks sound flat and lifeless in comparison to the original. The Model 204 will bring these tracks back to life without unmasking the compression artifacts.
RELATING THE FREQUENCY RANGES OF THE BIG BOTTOM AND AURAL EXCITER TO THE FUNDAMENTALS AND HARMONICS OF SOUND
Big Bottom Range Aural Exciter Range
MID MIN MAX MIN MID MAX
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Audible Harmonics
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6.0 Warranty & Service
6.1 Limited Warranty
PERIOD One year from date of purchase SCOPE All defects in workmanship and materials. The following are not covered: a. Voltage conversions b. Units on which the serial number has been defaced, modified, or removed c. Damage or deterioration: 1. Resulting from installation and/or removal of the unit. 2. Resulting from accident, misuse, abuse, neglect, unauthorized product modification or failure to follow instructions contained in the User's Manual. 3. Resulting from repair or attempted repair by anyone not authorized by Aphex Systems. 4. Occurring from shipping (claims must be presented to shipper). WHO IS PROTECTED This warranty will be enforceable by the original purchaser and by any subsequent owner(s) during the warranty period, so long as a copy of the original Bill of Sale is submitted whenever warranty service is required. WHAT WE WILL PAY FOR We will pay for all labor and material expenses for covered items. We will pay return shipping charges if the repairs are covered by the warranty. LIMITATION OF WARRANTY No warranty is made, either expressed or implied, as to the merchantability and fitness for any particular purpose. Any and all warranties are limited to the duration of the warranty stated above. EXCLUSION OF CERTAIN DAMAGES Aphex Systems' liability for any defective unit is limited to the repair or replacement of said unit, at our option, and shall not include damages of any other kind, whether incidental, consequential, or otherwise. Some States do not allow limitations on how long an implied warranty lasts and/or do not allow the exclusion or limitation of incidental or consequential damages, so the above limitations and exclusions may not apply to you. This warranty gives you specific legal rights, and you may also have other rights which vary from State to State.
204
6.2 SERVICE INFORMATION If it becomes necessary to return this unit for repair, you must first contact Aphex Systems, Ltd. for a Return Authorization (RMA number), which will need to be included with your shipment for proper identification. If available, repack this unit in its original carton and packing material. Otherwise, pack the equipment in a strong carton containing at least 2 inches of padding on all sides. Be sure the unit cannot shift around inside the carton. Include a letter explaining the symptoms and/or defect(s). Be sure to reference the RMA number in your letter and mark the RMA number on the outside of the carton. If you believe the problem should be covered under the terms of the warranty, you must also include proof of purchase. Insure your shipment and send it to: Aphex Systems, Ltd. 11068 Randall Street Sun Valley, CA. 91352 PH: (818) 767-2929 FAX: (818) 767 -2641
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7.0 Appendices
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Appendix A: Balanced and Unbalanced Lines and Operating Levels
Interfacing all types of equipment with balanced and unbalanced lines and can sometimes be troublesome. First you have to somehow connect balanced to unbalanced and then you have to deal with different levels. This tutorial will teach you about the principles of balanced and unbalanced lines, wiring standards, and how to effectively interface them. Standards Professional audio equipment usually comes equipped with inputs and outputs that are balanced using 3-pin XLR connectors and sometimes 1/4 inch phone jacks as well. This equipment most often is designed to operate at +4dBu, a professional industry standard. That translates to a magnitude of 1.23 volts RMS (Root-MeanSquared). Consumer gear has unbalanced I/O as standard, usually on RCA jacks. The normal operating signal level follows the IHF (Institute of High Fidelity) standard of -10dBV, or 0.316 volts (316mV) RMS. Converting to dBu dimensions, this works out to be the same as -7.79dBu. There is therefore a difference of 11.79dB between pro and consumer operating levels. Grounding There is the notion that some king of earthly "ground" exists out there that sinks all the noise and acts as some kind of a shield. You see wires connected to ground rods and water pipes that are supposed to get a good ground. This is not a correct interpretation of grounding from an audio standpoint. Proper grounding of equipment and wiring is important and you will gain a better understanding of that as you read along. Balanced -vs- Unbalanced Every audio signal is connected through a circuit. The circuit must contain two conductors to create a complete return path. In other words, a signal voltage is conducted to a piece of equipment by injecting a current into a wire. That current has flow though to the destination through the wire and return back to the source through another wire. Since audio is an alternating voltage, swinging through negative and positive polarity, the current through the two conductors changes direction each alternate half cycle. Which wire is the source and which is the return alternates accordingly. In this regard, balanced and unbalanced lines are the same. They both need two conductors. What makes a system unbalanced is when one of the wires is formed into a tube that wraps around the other conductor, without touching it, such that the outer conductor can be said to "shield" the inner conductor. This describes all of the coaxial cable used for video, cable-TV and radio as well as most of the high fidelity audio cables.
Balancing
If both conductors are identical insulated wires that are twisted together, then they form a balanced line. This describes telephone lines, microphone cables, and most professional audio cables. Typical balanced cables include an additional shield wrap around the twisted pair, but this is not strictly required for balanced lines to work properly. Many people, because they have more experience with unbalanced wiring, think that balanced is confusing. Believe it or not, balanced lines are really easier to understand than unbalanced. There is no grounding issue with balanced, and the way it works is perfectly natural and simple. Balancing naturally rejects hum and noise and eliminates all sorts of complications in interfacing.
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Balanced transmission works something like this. Your balanced input stage looks at the two wires and detects only the potential (voltage) difference between them. Anything that is the same on the two wires (for all practical purposes as seen measuring from ground) is called a common mode signal and is cancelled out by the differential amplifier. Figure 1 illustrates how the hum is induced into both wires equally and therefore is cancelled out. Since the balanced line has wires that are twisted together, each wire tends to pick up the same amount of induction from external sources. Induction will create no significant voltage difference between the wires, hence the noise (or hum) will not be picked up by the differential input stage.
Figure 1 Balanced Line Model
Figure 2 Unbalanced Line Model
It can be seen that the signal generator driving the twisted pair will cause a difference between the wires, and that signal will be readily picked up by the differential input stage. One of the beauties of the balanced line is that it is completely independent from ground. Nothing is connected to ground at all, nor does it care about ground. Nevertheless, most professional cable has an overall shield wrap that is intended to be connected somehow to ground. You may well ask why, and the answer is less than glorious. Simply, nothing is perfect, not even balanced cable. Under some circumstances the shield can overcome extreme interference problems that can't be adequately rejected by the twisted pair alone. Things like 2-way radios, television transmitters, and light dimmers can induce very heavy interference that may be reduced by shielding. You are going to find virtually all balanced cables include a shield so you need to deal with it, even if it is not actually needed. That subject will be addressed a little later.
Unbalancing
Unbalanced wiring works a little differently. Figure 2 shows the basic plan. In this case, the wires are not twisted, they are coaxial. The unbalanced input stage is somewhat like the balanced input stage because amplifies a difference signal, but this time it is the difference between two non-symmetrical conductors. To make things even less symmetrical, the outer conductor is connected to ground at both ends. The principle is that the outer shield conductor shields the inner conductor from induced noises. This can only work well if the cable is relatively short and the ground at each end of the cable is somewhat equal, i.e., there is no "grounding difference" that can cause current to flow through the shield conductor. Grounding difference is a serious problem in studios, because often the equipment grounds are connected to power outlet grounds, and there can be a significant difference of ac voltage between alternating wall outlet grounds. For this reason, unbalanced systems can sometimes never be made hum free, and just changing one piece of equipment in a studio can cause hum to appear somewhere else. When you are using unbalanced gear, it is a very good procedure to power all your equipment from one large power isolation transformer. At the very least, make sure all equipment is powered together off the same distribution panel circuit (same circuit breaker).
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Appendix B: Dealing With Grounds and Hum
Ground Loops
instruction Manual
Many people equate this term with hum, and that's just about the bottom line of it. If you have a ground sensitive system, like unbalanced audio equipment for example, then hum will result from ground currents that flow from the ac power system. It is sometimes very difficult to isolate and stop ground currents between unbalanced equipment, but it is quite easy to clean up balanced gear. That's why pro gear is always balanced! The cost of balancing is that of more expensive connectors, cable, and electronics but the cost is worth it when you depend on your audio quality. That's why the Model 204 is equipped with a fully balanced I/O. Now that we've sold you on only using really expensive pro gear, lets show you how to get away with the really cheap stuff! At least from the standpoint of killing ground hum. A ground loop is an ac current that has become routed through your audio ground system. The current comes mainly from ground potential differences that exist between different wall outlets that return to opposite phases at the power distribution panel. Secondarily, however, many pieces of equipment contain line filters and transformers that leak a small amount of ac power into the chassis and ground return. You may once have had the experience of getting zapped by touching two pieces of gear at the same time. That illustrated the ground loop effect - - straight through you! No matter what you do, you may not be able to prevent some of your equipment from generating ground currents. The most likely culprits are digital products because they use switching power supplies that require heavy line filters to prevent conducted EMI from going out of the box. Filters so employed very often take the ground leakage current right up to the UL safety limits. Although it won't kill you, that is a lot of ground loop current for audio cables to handle. There are basically three ways to attack the problem of a ground loop. First is to eliminate it from its source, and the second is to re-route it through another path. The third is to balance out your unbalanced audio interfaces. Identify the Sources A good way to identify grounding problems is to use a multimeter to check the ac voltage between the chassis of your various gear when no audio cables are hooked up and all gear is plugged in and switched on. Just start touching the two probes to the metal chassis of different pieces of gear. Ideally, you should always see zero volts. Warning! You may see as much as the whole line voltage between two different chassis! It does happen. This voltage between chassis will be responsible for your ground loop problems. If you find there is more than about 1 volt between equipment grounds, you should start looking for a remedy. Commonize the Power Try plugging all of your equipment into the same outlet strip. Get one that has enough outlets in one strip or string more than one together. Of course, you need to make sure you don't overload the one ac circuit your strip is plugged into. If the load is too great for one circuit, use a second or third circuit that is tapped off the same 120 volt phase in your distribution panel. That means all outlets should be on odd or even numbered circuit breakers. That's because, as you go down the column, the circuit breakers tap into alternating legs of your incoming electric power. Be sure you're always on the same leg. You can tell you're on the same leg by measuring the ac voltage between the hot slots of the different outlets you've chosen. It should be very low or zero. That will remedy 50 percent of the cases. Check the Cord Polarity For products that have 2-wire power cords, try reversing one of the power cords in the socket. That may reduce the ground current generated by the internal electronics of the offending gear.
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Appendices
Redirect Ground Loops Sometimes it just comes down to brute force grounding. That means providing such heavy, low resistance, ground current paths that little current is left to flow through your audio grounds. You can try adding heavy gauge, for example 12 gauge, copper wire from chassis to chassis. You will need to locate a metal screw that solidly binds to the metal chassis of the gear. You may even need to drill a hole through the chassis and install a screw yourself. Equipment in rack shelves can have their chassis grounded to the metal rack frame by a heavy wire and the frame itself can act as a brute force ground. You just have to try everything you can think of. Usually a combination of all these methods will be needed to completely clean up a badly humming audio system. Balance Out the Audio Remember, balanced lines are inherently hum free. If you can balance out your unbalanced equipment, you will be able to stop the hum. Pseudo Balancing You will find in Table 2 an interconnecting method called Pseudo Balanced. This works when connecting an unbalanced output to a balanced input. This breaks up the ground loop by requiring the shield to be grounded only at one end. For best results always ground the shield only at the receiving end. Level Interface Units Aphex manufactures the Model 124 Level Interface box which is designed to electronically convert two unbalanced inputs and outputs two balanced inputs and outputs, and at the same time translate the -10dBV IHF unbalanced levels to the pro +4dBu balanced levels. This cost effectively gives your non-professional unbalanced equipment a fully professional I/O equal to the world's best pro audio gear. Seriously consider putting one of these on each unbalanced piece of gear you use. Avoid Transformers The use of balancing transformers is an option, but you will invariably lose audio quality due to transformer limitations. Try everything else first.
Appendix C: Wiring Techniques
A true balanced line should be used wherever your equipment allows. Use "twisted pair" shielded cable. For unbalanced wiring you should use high grade, low capacitance shielded wire for best results. If you have an unbalanced output but have a balanced input, the "pseudo-balanced" configuration may help deal with ground loop hum. This method and others are illustrated in Table 2.
CONNECTOR WIRING STANDARDS
The 3 pin XLR, 1/4" (63.5 mm) TS mono phone and the 1/4" (63.5 mm) TRS stereo phone are the most commonly used line level connectors in pro audio. Less common is the use of the "RCA" phono jack, which is essentially a consumer type connector. The XLR and the TRS are three conductor and are used for balanced connections. The TS and the RCA are two conductor and are used for unbalanced connections. In addition to the three main contacts on an XLR there is also a grounding lug contact. This lug is connected to the connector's case (shell). In all Aphex products audio ground and chassis ground are one and the same. Aphex products that use XLR connectors tie Pin I to the XLR case automatically. Therefore it is not necessary to use the XLR case-ground lug. This also makes possible the use of XLR ground drop adapters (see Note 3).
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3-Pin XLR Pin-1 Pin-2 Pin-3 1/4" TS Phone Tip Sleeve 1/4" TRS Phone Sleeve Tip Ring RCA Center Pin Shell
instruction Manual
TABLE 1: The following wiring convention is now standardized in 17 countries including the USA. Please note that any equipment that still uses Pin 3 as positive on XLR connectors is not adhering to the standard. TABLE 1 - BALANCED & UNBALANCED CONNECTOR WIRING STANDARDS
Standard Wiring Convention (Balanced) Ground/Shield (Earth, Screen) Positive (Signal, High, Hot) Negative (Signal Reference, Return, Low, Common) Standard Wiring Convention (Unbalanced) Positive (Signal) Ground/Shield (Signal Reference/Return)
THE PIN 1 DILEMMA AND HOW IT AFFECTS CABLE SHIELD CONNECTIONS
The three main contacts on an XLR (or TRS) and the accepted wiring assignments shown above are only part of the picture. The standard for terminating ground is Pin 1 (Sleeve). But which ground? It could be connected to audio signal ground or chassis ground depending on the method of grounding used by the equipment manufacturer. In all Aphex products audio ground and chassis ground are one and the same. This is just good, common sense engineering practice (which is what you would expect from us, course). Unfortunately, many products are designed so that the noisy currents from the shield drain into signal ground instead of chassis ground. This practice creates a real problem for end-users. The appropriate overall grounding scheme of an audio system would be a lot easier to predict without this problem1. The standard balanced line wiring recommendation from Aphex Engineering is this: In the majority of cases maximum noise rejection occurs when the shield is connected to the input ground only (especially in locations with high levels of RFI). That means the sending end shield should be left disconnected. However, if you already have cables with the shield connected at both ends, go ahead and try them out. If you are connecting a fairly simple audio system it