Symetrix 528E User Manual
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Symetrix 528E User Manual

Voice processor
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528E Voice Processor

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  • Page 1 User’s Guide 528E Voice Processor...

  • Page 3: Important Safety Instructions

    User’s Guide 528E Voice Processor Before You Begin /32 What Ships in the Box Important Safety Instructions. or plug cord is damaged, liquid has been spilled or objects have fallen 1. Read these instructions. A 528E hardware unit. into the apparatus, the apparatus has 2. Keep these instructions. A detachable power cord. been exposed to rain or moisture, 3. Heed all warnings. does not operate normally, or has This User’s Guide. been dropped. 4. Follow all instructions. 5. Do not use this apparatus near Getting Help CAUTION water. This apparatus shall not be...

  • Page 4: Fast First Time Setup

    Connect a Mic or Line level source to the appropriate input connec- Output Connect to input of console, tor on the rear of the 528E. Be sure to set the Mic / Line switch to the tape recorder, etc. appropriate position and be sure to turn on phantom power if using a microphone that requires it. Next, connect the appropriate output of the Line Input Connect line-level source here. 528E to your monitoring system or mixing console. Finally, connect the Mic Input Connect microphone here 528E to an AC source of the proper voltage and frequency as marked Phantom Power Depress if mic requires phantom on the rear of the unit. powering. Caution: Failure to connect the 528E to the proper AC mains voltage may cause fire and/or internal damage. Warning: Lethal voltages are present inside the chassis. There are no user serviceable parts inside the chassis. Refer all service to qualified service personnel or to the factory. If you are using a condenser microphone, refer to “Phantom Powering Condenser Microphones” before depressing the Phan- tom Power switch.
  • Page 5 User’s Guide 528E Voice Processor Fast First Time Setup 3/32 ... continued Settings Set the controls and switches on the front of the 528E per the following table: Front Panel Control Setting Front Panel Control Setting MIC / LINE As required LOW EQ FREQUENCY 160 Hz (12 o’clock) -15 PAD LOW EQ BANDWIDTH 1.5 octaves (12 o’clock) MIC GAIN 12 o’clock LOW EQ CUT/BOOST 0 (12 o’clock) DE-ESS FREQUENCY 3K (12 o’clock) MID EQ FREQUENCY 2.5K (12 o’clock) DE-ESS THRESHOLD 0 (Full CW) MID EQ BANDWIDTH 1.5 octaves (12 o’clock) DE-ESS IN / OUT MID EQ CUT/BOOST 0 (12 o’clock)

  • Page 6: Front & Rear Panel Overview

    User’s Guide 528E Voice Processor Front & Rear Panel Overview /32 Mic Preamp MIC/LINE Selects between the Mic input (switch in) and Line input (switch out). MIC PRE-AMP DE-ESS (-dB) CLIP PHANTOM LINE -15 PAD Inserts 15 dB pad for strong mic signals. 528E VOICE MIC GAIN(dB) Sets the gain of the mic preamp for best compromise between signal-to-noise ratio PROCESSOR and headroom. -15 PAD MIC GAIN(dB) FREQUENCY THRESHOLD NORM CLIP Monitors inputs (mic and line) for clipping. Illuminates 3 dB below the actual clip point. PHANTOM Illuminates when 48V phantom power is present at the microphone input connector.
  • Page 7 User’s Guide 528E Voice Processor Front & Rear Panel Overview 5/32 ... continued Output Section GAIN Sets the overall gain of the 528E’s output over a +/- 15 dB range. MIC PRE-AMP DE-ESS (-dB) DOWNWARD EXPANDER (-dB) COMPRESSOR (-dB) LOW EQ MID EQ HIGH EQ OUTPUT LEVEL (VU) CLIP PHANTOM -20 -15 CLIP LINE NOTE: The actual adjustment point is in the expander/compressor’s VCA, which is...
  • Page 8 User’s Guide 528E Voice Processor Front & Rear Panel Overview /32 ... continued De-esser I/O OUTPUT TRS phone jack (wired unbalanced). This is the output of the de-esser. Inserting a connector into this jack does not interrupt signal flow to the 528E’s expander / compressor. INPUT TRS phone jack (wired unbalanced). This is the input to the expander / compressor. Inserting a connector into this jack interrupts signal flow from the mic / line inputs. Preamp Stage I/O PREAMP STAGE TRS phone jack (wired unbalanced). This is the output of the OUTPUT mic / line preamp. Inserting a connector into this jack will not interrupt signal flow to the 528E’s de-esser. LINE INPUT XLR female connector providing a 10k Ohm balanced bridging line input intended for signals ranging from -10 dBu to +4 dBu. MIC INPUT XLR female connector providing a balanced input suitable for low impedance microphones. 48V phantom powering is available at this connector. PHANTOM Pushbutton switch enabling 48V phantom power on the MIC INPUT. POWER...

  • Page 9: Voice Processing Tutorial

    User’s Guide 528E Voice Processor Voice Processing Tutorial /32 Basics The Symetrix 528E Voice Processor combines Symetrix’ program controlled interactive dynamic range processing technique with a three-band parametric equalizer. This combination of processors is similar to a voiceover or vocal signal processing chain as used in a recording or voiceover studio. “Program controlled” means the 528E’s dynamic range processor section analyzes incoming signals, then adjusts its release time to match the transient characteristics of those signals. This section of the manual contains a tutorial on the basics of dynamic range processing and equalization: the two key ingredients in the 528E. The tutorial information is intended to provide a background for the information found in the remainder of this manual. Dynamic Range Processing Dynamic range processors are used to fit wide-range signals into narrow-range transmission or storage channels. The dynamic range of acoustical signals found in real life usually far exceeds our capacity to store or transmit them. Confronted with this dilemma, audio engineers usually reach for a compressor/limiter or downward expander as a means to fit two-pound signals into one-pound bags. Compressor/limiters respond quickly to transients, and gently to normal speech level changes which keeps overall levels in check. The downward expander’s operation is the inverse of the compressor/limiter which prevents “pumping” and “breathing” even when high ratio compression is necessary. Because the compressor/limiter and the downward expander are interactive, the 528E always responds appropriately, while providing automatic control over a wide range of input levels. Strictly speaking, the terms compressor and limiter refer to two different devices. Oftentimes the two are combined into a single device called a compressor/limiter. Compressor/limiters usually perform as either a compressor or a limiter, but not both at once. Functionally, a compressor/limiter is a device that lets the user define, or predetermine, the maximum level of an audio signal. Expanders and gates are the functional opposites of compressors and limiters. Compressors continuously reduce the dynamic range of signals that are above threshold, while expanders continuously increase the dynamic range of signals that are below threshold. Limiters can be thought of as very high ratio compressors, and gates can be thought of as very high ratio expanders. In addition to their roles as remedial signal processors, compressors also have a creative role. You can use a compressor to increase the apparent sustain of a guitar, increase apparent loudness, improve the consistency of a bass by removing or reducing level changes, and many other things. Generally speaking, the settings for these applications are somewhat extreme, so experimentation is the name of the game.
  • Page 10 User’s Guide 528E Voice Processor Voice Processing Tutorial 8/32 ... continued clipping is the dynamic range. To find the 528E’s dynamic range with 50 dB preamp gain, subtract -89 from 18. The result (113 dB) is the dynamic range. Dynamic Range of Sounds and Signals The other definition of dynamic range describes actual level changes, or the range over which signals fluctuate. The signals under discussion here are electrical representations of sounds, so it follows that sound has dynamic range. The dynamic range of the human voice, from a whisper to a shout, is well over 100 dB. Thus, the microphone converts the sound pressure of a voice going from a whisper to a shout into an electrical output signal having the same dynamic range. Why Dynamic Range Processors are Necessary For signals to stay below distortion and above noise, their actual dynamic range must be kept within the specified dynamic range of the circuits through which those signals flow. Unfortunately, the actual dynamic range of real world signals often exceeds the available dynamic range of even the best equipment. For example, the dynamic range of the best analog tape recorders is around 80 dB, while digital recorders top out at around 96 dB. As good as these machines are, there’s still not quite enough room for very wide dynamic range signals. In order to maintain a 60 dB signal-to-noise ratio (to keep the signals 60 dB above the noise floor), the dynamic range of signals stored on the analog tape machine would have to be restricted by 20 dB, while the digital recorder would be restricted by 36 dB. A compressor or limiter is often used to reduce dynamic range by setting an upper limit on the larger signals. In some cases, it’s better to put processing to work on the lower end of the dynamic range than on the upper end. In other words, instead of reducing the amount of change at the upper end of the dynamic range with a compressor or limiter, increasing the amount of change at the lower end of the dynamic range with a downward expander or gate.
  • Page 11 User’s Guide 528E Voice Processor Voice Processing Tutorial /32 ... continued maximum. But if that same signal is passed through an expander operating at a 1:2 ratio, the same 2 dB change at the expander’s input becomes a 4 dB change at its output. However, that signal would be 1 dB over maximum, causing distortion. Linear expanders must be used with care, because very few systems have enough headroom to handle the upward dynamic range increase they produce. The kind of processor most commonly called an expander is really a downward expander, because it only affects signals below threshold. This gives the operator control over the expander’s activities, allowing it to be used to expand the usable dynamic range of the system without running out of headroom. Note: in the interests of clarity and brevity, the term expander will be defined as a downward expander from this point forward in this manual. How Expanders Increase Usable Dynamic Range The lower limit restriction of a system is the noise floor, which is usually well below the 528E’s lowest expander threshold (-50 dBu). It’s important to keep in mind that while the signal levels may change greatly, the noise usually doesn’t change very much. The action of the expander increases the dynamic range of all signals below threshold. This action increases the apparent loudness of signals, while decreasing the apparent loudness of the noise. For example, an expander operating at a ratio of 1:2 will cause an input signal that falls 10 dB below threshold to fall 20 dB at its output. The downward action of the expander reduces the noise floor by the same ratio applied to the signal. Since the relationship between the signal and the noise stays the same, the noise is reduced 20 dB by the action of expander, which is responding to a 10 dB drop in the signal with its 1:2 ratio. De-essers A de-esser is another type of dynamic range controller that’s specially designed to regulate high frequency content. The technique was originally developed for motion picture dialogue recording, when it was discovered that speech sounded more natural and pleasing when the accentuation of sibilants was reduced. By sensing and limiting certain selected frequencies, the de-esser is intended to provide more specific control over some of the higher frequency vocal sounds that tend to become overemphasized especially when the talker is close-miked.
  • Page 12 User’s Guide 528E Voice Processor Voice Processing Tutorial 0/32 ... continued separate (even while the control circuit tells the VCA whether to turn the gain up or down), you can equalize the sidechain without changing the EQ in the main audio path. Removing unwanted frequencies from the control signal before it actually reaches the VCA prevents those frequencies from being used to create gain changes. Applications utilizing the sidechain may be found in the Applications section. Equalization Equalization is one of the most powerful tools available to the audio engineer. It is, quite possibly, the first signal modification device that most people experience (aside from the volume control). This experience takes the form of using the tone controls found on most consumer audio equipment. Even in this primitive form, simple tone controls can shape and alter a sound, giving us pleasure or pain, evoking emotion, or simply enhancing our listening pleasure. The parametric EQ in the 528E provides both creative and corrective frequency shaping - it can be used to create a more pleasing sound, and to correct frequency response problems. The equalizer has a symmetrical ±15 dB boost/cut response. The term “parametric” simply refers to the fact that the primary operating parameters of the equalizer may be altered by the user. The user adjustable parameters are: • center frequency (or fc, expressed in Hz), • bandwidth (sometimes called “Q,” or selectivity, expressed in octaves), and • the amount of cut or boost (expressed in dB). These terms are defined as follows: Center Frequency is defined as the frequency (in Hz) of the middle of the bell shaped response curve formed by a filter. Bandwidth is the width of the bell shaped curve, measured between its -3 dB points. The measure of bandwidth in audio equalizers is usually given in octaves or parts of an octave. Cut or Boost is given in dB, at the center frequency. Equalization Tutorial Equalization is nothing more than selectively (or not) amplifying a signal based on frequency. Since audio signals consist of combinations of fundamental signals and their harmonics, changing the tonality or the spectral balance of a signal involves nothing more than altering the relationship of the fundamental to its harmonics, and of the harmonics to themselves. Each harmonic is responsible for one aspect of the audible character of a signal; knowing these relationships allows you to quickly...
  • Page 13 User’s Guide 528E Voice Processor Voice Processing Tutorial /32 ... continued It was Leopold Stowkowski who said “If I had a thousand bass viols I could use them all!” This is not as extreme as it may sound. A bass viol, even though it is reinforced by its sounding board, generally plays single notes and possesses little dynamic range. In a large orchestra, as many as eight bass viols may be used. A total of 1000 bass viols in this case would only give an additional 21 dB of level, which is not an inordinate amount given a glance at Mr. Fletcher’s equal loudness curves. Pay attention to this range because the overall musical balance of your program can be controlled by equalizing or attenuating the 100 Hz range. Telephone Quality The ear is reasonably sensitive in the midrange frequencies, and sound restricted to this range has a telephone-like quality (which is generally why telephone-quality frequency response covers the 300-3 kHz range). If you make the 6th octave (500-1024 Hz) louder with respect to the other octaves, the subjective result is a horn-like quality. If you emphasize the 7th octave (1000-2000 Hz), the effect is one of tinniness. The fundamental tones in most music lie equally above and below middle C (261 Hz), from 128 to 512 Hz. As most instruments are rich in the first overtones, the majority of sound energy is found up to the 2.5 kHz range. Music editors and others engaged in listening to music over long periods find that listening fatigue can be reduced by attenuating the 5th, 6th, and 7th octaves by about 5 dB. Lisping Quality The 3 kHz range delivers a generous stimulus to the ear. At very loud levels the region of greatest ear sensitivity shifts downward from 5 kHz; this is why many “PA” speakers have broad peaks in this region. A characteristic of low-level signals peaked at 3 kHz is a “lisping” quality, and the total inability to distinguish labial sounds such as m, b, and v. In wide-range lower level systems, a peak in the 3 kHz region has a masking effect on important recognition sounds, and on others which lie above 4 kHz. Brilliance and clarity are lost and without attenuation of this region, an unconscious strain with increasing fatigue is felt according to the amount of 3 kHz boost. Presence Range The usual band affecting clarity in male speech is 3000 to 6000 Hz. In a woman’s voice, the fundamentals are roughly an octave higher than a man’s, and a woman’s range of consonant clarity lies between 5000 and 8000 Hz (the high-end of this range approaches a region of hearing insensitivity in humans). Furthermore, the total range of a woman’s voice is about half that of a mans, stimulating fewer hearing nerves, and for this reason, is consequently still weaker upon reception.
  • Page 14 User’s Guide 528E Voice Processor Voice Processing Tutorial 2/32 ... continued than stereo), and as many mixers contained rotary mix pots as those that used slide pots. The value of individual channel equalization was known, but it was both technologically and financially prohibitive. The article concludes thusly: “With the advent of stereo and three-channel recording, nearly three times the equipment, with more elaboration, seems indicated, and expansion of console area in the horizontal plane offers the only direction in which to proceed. But a single engineer has arms only so long.” How times have changed! Using the Parametric Equalizer Great care must be exercised when using equalization. The following paragraphs give some general hints and precautions for using the 528E’s parametric equalizer (or any other equalizer, for that matter). Beware of Distortion and Noise When a frequency or group of frequencies are boosted, the overall operating level is boosted as well. For example, 12 dB of boost (no matter what the frequency) increases the 528E’s output level 12 dB (at that frequency). This kind of boost reduces headroom by 12 dB in every circuit from the 528E’s own line driver to the last device in the signal chain (transmitter, tape machine, or what have you). Unless signal levels are very low to begin with, the 528E’s output gain will have to be reduced to compensate for increased levels whenever the equalizer is used for boost. The Clip LED in the Output LED meter monitors levels in the equalizer as well as at the output of the 528E. If the Clip LED glows, try switching the equalizer to Bypass. If the LED still glows, reduce the setting of the Output Gain control. If switching the equalizer to Bypass eliminates the clip indication, then the input level must be reduced via the Mic Gain control or by lowering the level of the line input. On the other hand, if the levels within the 528E are too low to start with, using the equalizer for boost may increase noise to unacceptable levels. If levels are too low, increase the preamp gain (or the output level of the device feeding the line input).
  • Page 15 User’s Guide 528E Voice Processor Voice Processing Tutorial 3/32 ... continued generally only useful for remedial work. Broader bandwidths are less obnoxious, more pleasing sounding, and easier to work with (especially if you’re boosting a range of frequencies). Try to avoid massive amounts of boost or cut. If you’re only trying to impart a flavor (like sprinkling salt and pepper on a meal), then 6-8 dB of boost or cut should be all that you need. A wide bandwidth cut is equivalent to a boost at the frequencies surrounding the cut. A quick way to figure out what’s going on is to set the level of one band of the equalizer to full boost (+15 dB), then switch to the frequency control and vary the frequency of that band of the equalizer while listening to program material fed through the unit. This usually makes quick work out of finding the region that you want to work on. Now reduce the level setting to something tasteful. A common problem when trying to set an equalizer for someone’s voice is converting the descriptive adjectives that people use in describing the character of a voice into the numbers that make equalizers happy. The following table list some commonly used adjectives and their corresponding frequency ranges. Range Description (women) Range Description (men) 100-250 Hz Fullness 75-200 Hz “Balls”, rumble, heaviness 250-400 Hz Bassiness, bigness 200-300 Hz Bassiness, bigness 400-600 Hz Warmth 400-600 Hz Chesty 600-1 kHz...
  • Page 16 User’s Guide 528E Voice Processor Voice Processing Tutorial /32 ... continued...

  • Page 17: Using The 528E

    User’s Guide 528E Voice Processor Using the 528E 5/32 This section is intended for more advanced users. If you are a first-time user, we recommend that you start out by using the procedure found in “Fast Setup.” Block Diagram The block diagram below is the block diagram for the 528E. Please take a moment and take note of the following: • The equalizer and de-esser are hard-wire bypassed by their In/Out switches. • The interstage patch points use TRS jacks wired for unbalanced operation. • The interstage patch points are half-normalled. The send jack does not break the signal flow. The output level of the 528E can be set to either line level or mic level. The switch for this function is internal to the unit. Refer to Appendix A. MIC GAIN FREQUENCY THRESHOLD +48V/BYPASS IN/OUT CLIP DE-ESS IN/OUT -15dB PHANTOM PREAMP P AD POWER DE-ESS SUPPL Y...

  • Page 18: Level Setting

    User’s Guide 528E Voice Processor Using the 528E /32 ... continued The interstage patch points use TRS jacks with the ring and sleeve connections connected to circuit ground. The jacks are half-normalled (only input breaks normal). Level Setting For optimum noise performance, correct level settings are a must, especially for microphone sources. You should operate the 528E’s mic preamp at the highest gain possible without overload. Extremely hot signals may require using the -15 dB pad switch. The 528E expects line level signals to fall in the +4 dBu region. Lower signal levels are okay, but the noise performance may suffer as there is no gain trim control for the line input. The Clip LED in the mic input section of the 528E actually monitors the output of the Mic-Line switch. If the LED glows, and you are using the Mic input, then reduce the setting of the Mic Gain control until the LED no longer glows. If you are using the Line input, reduce the level of the device driving the 528E. The Clip LED in the Output LED meter monitors levels in the equalizer as well as at the output of the 528E. If the Clip LED glows, try switching the equalizer to Bypass. If the LED still glows, reduce the setting of the Output Gain control. If switch- ing the equalizer to Bypass eliminates the clip indication, then the input level must be reduced via the Mic Gain control or by lowering the level of the line input. Operational Details This section describes the details of operating the 528E. Usage information can be found later in this section. The 528E accepts monaural analog input signals at mic or line level, processes them, and delivers them back to you as bal- anced line, unbalanced line or balanced mic level signals. Stand-alone Operation A vast majority of users use the 528E as a stand-alone device. Here the 528E replaces their usual microphone preamp and either feeds their tape machine or workstation directly, in essence becoming a one-input, one-output console. For best results, the 528E should replace the mic preamp in your console or recording chain. If you have to plug the 528E into a microphone input (-40 dBu nominal level), then you’ll need to pad (attenuate) the output of the 528E down to microphone level. An internal jumper connection reduces the 528E’s output to this level. Although a far preferable connection would be to bypass your console’s mic preamp, this will work. When configured for mic-level output, the 528E’s circuitry doesn’t care if phantom powering is or isn’t present at the console’s mic input. Appendix A contains instructions for altering the output level of the 528E.
  • Page 19 User’s Guide 528E Voice Processor Using the 528E /32 ... continued Using the 528E as a Channel Insert Device The 528E can also be used as a channel-insert device with your console. Use the 528E’s line input and line output as shown below. LINE INPUT MIC INPUT BALANCED OUTPUT P E S OUTPUT STAGE EQUALIZER EXPANDER/COMPRESSOR DE-ESS PRE-AMP STAGE UNBALANCED PHANTOM OUTPUT INPUT OUTPUT INPUT OUTPUT SIDECHAIN INPUT OUTPUT...
  • Page 20 SIDECHAIN INPUT OUTPUT INPUT OUTPUT conscious. The figure right illustrates this patch. You can find TIP=RETURN out more about using the sidechain later in the next section. RING=SEND NOTE: SPECIAL WIRING NEEDED INPUT TO RING OUTPUT TO TIP Tips and Techniques for Using the 528E Following are some tips and techniques for using the 528E. You should consider any settings given as starting points for de- veloping your own settings. Metering The 528E has several LED bargraphs that serve as gain reduction and output meters. The gain-reduction meters indicate the change, from unity gain, for their respective function and the LEDs read (and move) from right to left. When operating as a level meter, the LEDs read (and move) from left to right. Each meter has its own scale markings, as shown on the front panel. Gain Setting There are two places to adjust the gain of the 528E: at the mic input, before any processing, and at the output. An understand- ing of this topic is essential to getting the most from your 528E. A more basic discussion can be found under the heading, “Level Setting,” in the previous section. First, the mic input gains. You make best use of the 528Es signal-to-noise ratio by ensuring that your mic-level input signals are adjusted to fit within the headroom of the mic preamp. Doing so ensures optimum dynamic range through the mic preamp and succeeding processors. With the De-esser, Expander/Compressor, and EQ sections temporarily set to Bypass and the Output Gain control set to 0 dB (12:00 o’clock), set the Mic Gain control so that the Output Level display indicates levels in the -10 to 0 VU range. The Clip LED should never illuminate on signal peaks. Remember to restore the settings of the various...
  • Page 21 User’s Guide 528E Voice Processor Using the 528E /32 ... continued meter illuminates. The red Clip LED should never illuminate. The output Clip LED also monitors the EQ section. If the Clip LED illuminates, reduce the Output Gain control setting slightly. You may need to increase the gain of some device following the 528E to achieve the same overall level. Equalization Bandwidth specs, in octaves, for some popular equalizers. Name BW (min) BW (max) API 550 1.6 Focusrite 0.6 Neve V3 0.2 SSL G 1.4 SSL E 0.5 The 528Es parametric equalizer has three overlapping bands. Each band can operate as a peaking or dipping equalizer. The boost and cut range for each band is ±15 dB. The bandwidth may be varied from 0.3 to 4-octaves wide. Since the bands overlap, it is possible to apply equalization at the same frequency in two places. Doing so could conceivably increase the signal level by 30 dB at one frequency. You may need to reduce the Input or Output Gain to avoid distortion. Like- wise, large amounts of boost in any one band may require reducing the setting of the Output Gain control to prevent overload. Let the Output Clip LED be your guide. Electronic considerations aside, one of the contributing factors to an equalizer’s sound is its bandwidth. The table above lists the bandwidths (octaves) for several (possibly) familiar equalizers, as found on their respective mixing consoles. While we make no promise that the 528E will sound the same, these settings may be a good starting point if one of these equalizers is within your frame of reference. A parametric equalizer offers perhaps the greatest flexibility of any type of equalizer, however it can be more difficult to arrive at a setting than with other equalizers. A good strategy for setting any equalizer is to set the level control for maximum boost,...

  • Page 22: Downward Expander

    User’s Guide 528E Voice Processor Using the 528E 20/32 ... continued Downward Expander The downward expander reduces its gain for any signal level below its threshold setting. Typically, downward expanders are used to remove noise or unwanted signal from an audio signal by simply lowering the gain when the overall level falls below threshold. Think about using the expander when you are faced with a noisy signal (not necessarily hiss) or when heavily compressing a voice and you want to remove some of the less desirable artifacts (false teeth rattling, lip smacking, tongue noise, etc.) You can also use the expander to help remove microphone leakage from a signal. Start by setting the threshold so that the expander causes gain reduction (left LED meter) as the signal falls in level. Increasing threshold levels (less negative numbers) cause further reductions in the overall gain as the signal level falls. Using the Sidechain The sidechain is a patch point in the control circuit of a dynamic range processor, which provides access to the part of the circuitry that tells the VCA what to do. The 528E’s sidechain routes through a rear panel TRS jack that allows the control signal to be processed outside the unit. Refer to the block diagram at the beginning of this section. Notice the sidechain connections that come from the compressor/ downward expander section. These connections allow access to the audio signal at the input to the control circuit that drives the dynamics processor. This control signal is derived from, but kept totally separate from, the audio signal path, which means that the control signal can be processed outside the 528E without actually processing the signal that’s going through the VCA (the audio signal itself). This presents some very interesting possibilities for changing or improving the operation of the dynamic range processor. The best use of the sidechain is to make the action of the 528E’s compressor/downward expander frequency dependent, that is, to make it respond more (or less) to certain frequencies. Because the audio signal and the control signal remain completely separate (even while the control circuit tells the VCA whether to turn the gain up or down), you can equalize the sidechain without changing the EQ in the main audio path. Removing unwanted frequencies from the control signal before it actually reaches the VCA prevents those frequencies from being used to create gain changes. Applications utilizing the sidechain may be found in the next section of this manual. The Voice Symmetry Switch Human speech, especially male human speech, contains a great deal of asymmetry. In broadcast (especially AM broadcast), this wastes transmitter power because the asymmetrical waveforms do not utilize the full power of the modulator. The bottom line is that you risk negative overmodulation if you don’t correct speech asymmetry before the modulator. The Voice Symmetry switch corrects asymmetric speech waveforms before they get to your board; an added bonus is that you can apply the correc-...

  • Page 23: Broadcast Applications

    User’s Guide 528E Voice Processor Applications 2/32 The 528E Voice Processor was designed to make the same kind of specialized processing that’s applied to voice-overs and vocal tracks in recording studios available for use in broadcasting, paging, public address and sound reinforcement. In a recording studio, four or five separate pieces of equipment are usually patched together to obtain the kind of processing pro- vided by the 528E. For the highest level of versatility, we recommend making the output/input patching and sidechain connections available by wiring the unit to a patch bay. Be sure that the interstage patch points are normalled together (we recommend half-normalling) and that the sidechain connection terminates in two half-normalled jacks. This allows access to the individual sections of the 528E, provides for easy use of the sidechain, and allows the processing order to be changed at will (to place the parametric in the sidechain, for instance). The following discussions illustrate some of the more useful applications for the 528E. Because of its versatility, combinations of the applications described here will normally be used. Broadcast Applications With the 528E, a variety of common problems can be corrected, and overall sound quality can be greatly improved. In addition to its “normal” use with announce mics, there are several more specialized uses for the Voice Processor. This section provides general operating guidelines for the various parts of the 528E, and also describes typical applications used in the production room for special effects, in the news room for cleaning up actualities and phone feeds, and in television for PA feed to a studio audience. The applications that follow are merely operational guidelines for the Voice Processor. The particular kind of processing ap- plied in any given situation must be determined by the problems encountered, and by the dictates of the format. What’s neces- sary or appropriate in one case, may not be at all proper in another. Announce Mics - Compressing, Limiting, Expanding The 528E’s dynamic range processor is used to control both over-modulation and noise. Noise, in this case, may be electrical- ly induced (hum, buzz, etc.), or acoustically transferred (paper rattling, cart solenoids, air conditioning, etc.), since the down- ward expander attenuates all below threshold signals without regard to origin. Careful adjustment of the two threshold controls allows the operator to put the 528E to work on any portion of the dynamic range. The expand threshold control governs the 528E’s activity in the lower part of the dynamic range, while the comp threshold governs activity in the upper part of the range. For smooth overall dynamic range processing that will tend to “homogenize” the sound and remove only very low level noises, use a gentle compression ratio with a relatively high comp threshold, and a relatively low expand threshold.
  • Page 24 User’s Guide 528E Voice Processor Applications 22/32 ... continued Cleaning Up News Feeds Use the de-esser to reduce unnatural high frequencies, the compressor/limiter to prevent overload, the expander to eliminate noise, and the parametric to make the feed sound better and/or get rid of interference (hiss, noise, extraneous sound, etc.). Actualities carts that are prepared with the 528E produce an end product with better intelligibility and improved signal to noise ratio. The object of the processing is to keep dynamic range within the real limits of the recording equipment, to eliminate extraneous noise, and to get better sound. Increasing Gain Before Feedback To optimize a PA system’s response for minimum feedback, tune out the feedback using the parametric equalizer. To find and eliminate resonances that can become feedback problems, turn the system on, with the microphone(s) and speaker(s) in place as they will normally be used, then follow the sequence below. Gain before feedback should increase about 6dB (perhaps as much as 15dB) with this technique. Note the settings of each of the compressor controls. Temporarily set the compressor ratio to 10:1. Increase system gain very carefully until a feedback frequency becomes slightly audible. With the bandwidth set at about .3 octave, and the cut/boost control set for about -15dB, tune the frequency control of one section until the feedback is no longer audible. Increase system gain until feedback becomes slightly audible again. If it’s the same frequency that was heard first, readjust the same frequency and bandwidth controls until it again subsides. If it’s a new frequency, repeat Step 2 using another of the EQ sections. Increase gain again to find the third most prominent feedback frequency. Repeat Step 2 using yet another of the EQ sec- tions. Reduce system gain to normal operating levels. Parametric EQ in the Sidechain The parametric equalizer can be placed in the sidechain of the dynamic range processor to make compression, limiting, or expanding action frequency sensitive. The equalizer is patched into the sidechain, so the audio signal that will ultimately be-...
  • Page 25 User’s Guide 528E Voice Processor Applications 23/32 ... continued NOTE: The ability of the expander to discriminate between wanted and unwanted signals is determined in part by mic tech- nique. Be particularly careful of high frequency sounds entering the side or rear pattern of a cardioid mic. Most cardioids exhibit a sharply rising off-axis response characteristic at higher frequencies. Check the off-axis curve (the lower one) in the manufacturer’s literature. If there’s only a 3dB to 6dB difference between the on-axis (front) response and the off-axis (side or rear) response in the 5kHz to 10kHz region, high frequency sounds will be picked up by the side or back of your mic. Use the mic’s directional pattern to keep other sources as far off-axis as possible - do everything you can to extract all the source-to-source discrimination possible through good mic technique. The sounds picked up by individual mics must be pri- marily the sound of the desired signal, or the expander won’t be able to tell the difference. Using Reverb or Effects Effects usually require another mixer input for effects return. However, the 528E’s patching connections can be used to feed a signal to the effects unit, and the output stage input can be used to return the effects signal to the 528E’s output. The only requirement is that the effects device have a mix control to set the direct/effects signal mix. Vocal Processing - Recording and Reinforcement The 528E handles a wide variety of program material with ease. When recording vocals, the undesirable side effects that usually result from high ratio comp/limiting, like headphone leakage and room noise, can be reduced with the 528E’s interac- tive expander processing. During mixdown the 528E not only provides compression, but also eliminates the noise that often accompanies vocal tracks that are processed with high frequency EQ, compression, or both. In sound reinforcement situations, if the threshold has been set correctly, the expander will attenuate whenever a mic is not in use, eliminating extraneous pickup of stage sounds, and reducing feedback from monitor speakers. The operating principle is the same for both the recording and reinforcement situations. Adding Dynamics, or “Punch”...

  • Page 26: Technical Tutorial

    User’s Guide 528E Voice Processor Technical Tutorial 2/32 This section discusses a multitude of things, all related to getting signals in and out of the 528E. Matching Levels vs Matching Impedances In any audio equipment application, the question of “matching” inevitably comes up. Without digging a hole any deeper than absolutely necessary, we offer the following discussion to (hopefully) clarify your understanding of the subject. Over the years, we have all had impedance matching pounded into our heads. This is important only for ancient audio sys- tems, power amplifiers, and RF. Technically speaking, the reason is power transfer, which reaches a maximum when source and load are matched. Modern audio systems are voltage transmission systems and source and load matching is not only unnecessary, but undesirable as well. • Ancient audio systems operate at 600 ohms (or some other impedance value), and must be matched, both at their inputs and at their outputs. Generally speaking, if you are dealing with equipment that uses vacuum tubes, or was designed prior to 1970, you should be concerned about matching. These units were designed when audio systems were based on maxi- mum power transfer, hence the need for input/output matching. • Power amplifiers are fussy because an abnormally low load impedance generally means a visit to the amp hospital. Thus, it’s important to know what the total impedance of the pile of speakers connected to the amplifier really is. • RF systems are matched because we really are concerned with maximum power transfer and with matching the imped- ance of the transmission line (keeps nasty things from happening). Video signals (composite, baseband, or otherwise) should be treated like RF. Some folks seem to believe that balanced/unbalanced lines and impedances are related; or even worse that they are associ- ated with a particular type of connector. Not so. Unbalanced signals are not necessarily high-impedance and balanced sig- nals/lines are not necessarily low-impedance. Similarly, although 1/4-inch jacks are typically used for things like guitars (which are high-impedance and unbalanced), this does not predispose them to only this usage. After all, 1/4 inch jacks are sometimes used for loudspeakers, which are anything but high-impedance. Therefore, the presence of 3-pin XLR connectors should not be construed to mean that the input or output is low-impedance (or high-impedance). The same applies to 1/4-inch jacks. So, what is really important? Signal level, and (to a much lesser degree), the impedance relation between an output (signal source) and the input that it connects to (signal receiver).

  • Page 27: Polarity Convention

    User’s Guide 528E Voice Processor Technical Tutorial 25/32 ... continued suitable condenser microphones. The microphone input accepts signal levels from -60 to -5 dBV (+10 dBV with the -15 dB pad). The line input is designed to accept nominal line level: +4 dBu. The output line driver delivers +4 dBm into 600-ohm or higher balanced loads. An internal switch converts the line level output to microphone level, or -36 dBu. An unbalanced output is also available via a 1/4" TRS phone jack. This jack is always line- level and is unaffected by the internal switch. When using the 528E with HAM radio equipment, it may be necessary to build an “L” pad attenuator in order to level match the 528E’s unbalanced 1/4” TRS output to a HAM radio transceiver’s unbalanced input. The 528E has a level of -2 dBu (-10 dBV) at it’s unbalanced output which translates to 0.615 volts RMS. The typical HAM radio transceiver has an input impedance of 10k Ohms so it would be expecting a level of 0.100 volts RMS. Knowing this, one can build an “L” pad attenuator with a 3600 Ohm series resistor followed by an 820 Ohm resistor to ground. This will give approximately 15.58 dB of attenuation thus providing a suitable level to the HAM radio transceiver input. I/O Impedances The 528E is designed to interface into almost any recording studio or sound reinforcement application. This includes: • 600 ohm systems where input and output impedances are matched. • Unbalanced semi-professional equipment applications. • Modern bridging systems where inputs bridge and outputs are low source impedances (voltage transmission systems). The 528E’s microphone input is intended to bridge a 150-ohm balanced source. The actual input impedance is approximately 8-kilohms. 48V phantom powering for condenser microphones is present if the Phantom Power switch has been depressed. Refer to the discussion of phantom powering on the next page for additional information. The 528E’s line input impedance is 10-kilohms balanced, and 10-kilohms unbalanced. The inputs may be driven from any source (balanced or unbalanced) capable of delivering at least -10 dBu into the aforementioned impedances. The 528E’s output impedance is 200 ohms balanced, 100 ohms unbalanced. The output line driver delivers +18 dBm into a 600-ohm balanced load or +18 dBm into 600-ohm unbalanced loads. Polarity Convention The 528E uses the international standard polarity convention of pin 2 hot. Therefore:...
  • Page 28 User’s Guide 528E Voice Processor Technical Tutorial 2/32 ... continued grounded at the 528E, rather than at the other end of the cable. The price, regardless of whether or not pin 3 is grounded is 6dB less output level. This can be easily made up via the output gain controls. If your system is wired with pin 3 hot, pin 2 must float if you are driving an unbalanced load. The 1/4-inch unbalanced output uses a TRS female jack with the ring contact wired to circuit ground. This jack is unaffected by the internal output level switch. Unlike the XLR connector, using this jack corrects the gain so that it is unity. The interstage patching jacks are half-normalled (only the input jack breaks normal) TRS jacks wired for unbalanced operation. This means that the tip is the signal connection, ring and sleeve are ground. This method of connection allows either TRS or TS plugs to be used, with either balanced or unbalanced inputs or output on the remote equipment. Aside from that, the TRS jack grabs the plug better. Ensure that your plug is fully inserted into the jack. The sidechain access jack for the dynamics processor uses a TRS jack wired as an insert jack. This means that the ring OUTPUT STAGE EQUALIZER EXPANDER/COMPRESSOR DE-ESS PRE-AMP STAGE UNBALANCED connection is the send to and the tip connection is the return OUTPUT INPUT OUTPUT INPUT OUTPUT SIDECHAIN INPUT OUTPUT INPUT OUTPUT from the remote processor. The figure below shows the wiring...

  • Page 29: Further Information

    User’s Guide 528E Voice Processor Technical Tutorial 2/32 ... continued Phantom Powering Condenser Microphones Most modern condenser microphones have provisions for being remotely powered via the microphone cable. The dominant system in use today is the phantom power system which is compatible with both condenser and non-condenser microphones (dynamics, ribbons, etc.). If your microphone’s data sheet says that it is phantom powered, the 528E can power it. Another remote powering system exists called A-B powering, modulation lead powering, or T system. A-B powering is incom- patible with phantom powering as well as other non-powered microphones. The technical requirements for operation and/or compatibility are: • The microphone must have a balanced, low-impedance output • The balanced output must be floating with respect to ground. If there is a center tap, it must also float with respect to ground. (In the past, it was common to ground the center tap of the microphone’s output transformer. This was especially true of ribbon microphones.) Further Information Much more information including an online tutorial, customer submitted settings, frequently asked questions and trouble shoot- ing information can be found on the Symetrix Knowledge Base at (http://support.symetrixaudio.com).

  • Page 30: Troubleshooting Chart

    User’s Guide 528E Voice Processor Troubleshooting 28/32 Troubleshooting Chart SyMPTOM PROBABLE CAUSE No output Check cables and connections. Are inputs driven by outputs, and outputs driving inputs? Verify cables, source and load by patching input and output connections together at the unit. Check for AC power presence. Power LED on? Check output by plugging headphones into output connector (use an adapter). Are the LED displays operating? Is the 528E set for mic-level output? Is the Mic/Line switch set correctly? Hum or buzz in output Check input and output connector wiring. Ground loop. Check related system equipment grounding. Are all system components on the same AC ground? Distortion Check input signal. Is it too hot, or is it already distorted? Is the Output display indicating clipping? Is the input clipping? Check output loading. Should be above 600 ohms? Are the power amplifiers clipping? Is something else clipping? Is the 528E set for mic-level output, driving a line-level input, with the 528E’s gain set fairly high and upstream devices contributing a significant amount of gain? Noise (hiss) Check input signal levels and level control settings. The Output display should indicate signal up to but not including the Clip LED. Check gain settings on upstream equipment. Is the input signal already noisy? The system gain structure should be such that the 528E operates at or near unity. Is the 528E set for mic-level output, driving a line-level input, with the 528E’s gain set fairly high and...

  • Page 31: Product Specifications

    User’s Guide 528E Voice Processor Product Specifications 2/32 Inputs Overall Performance Data Controls and Switches Mic Gain, Phantom Power, Frequency Response 20 Hz to 20 kHz Mic/Line (+0, -0.5 dB), EQ cut, compressor out, Mic and Line Input Connectors XLR-female (2) downward expander out, Clip LED Lights at +17 dBu output level de-esser out from mic preamp or line input amplifier THD + Noise 0.05%, 20 Hz to 20 kHz, Microphone Input Type Balanced Transformerless, +4 dBm output Low Impedance Noise Floor Better than -89 dBu, Phantom Power (DIN 45 596) +48V, nominal 20 Hz to 20 kHz Microphone Preamp Gain 22 to 60 dB (pad out) 7 to 45 dB (pad in)

  • Page 32: Architects And Engineers Specifications

    User’s Guide 528E Voice Processor Architects and Engineers Specifications 30/32 528E Architects and Engineers Specifications The voice processor shall be capable of all signal processing functions commonly found on a mixing console input channel, including microphone signal preamplification, line input buffering, simultaneous de-essing, downward expansion, compression/ limiting, and parametric equalization. The unit shall have a low-noise, low distortion microphone preamplifier with variable gain (22 dB to 60 dB) and switchable (on/ off) +48V phantom power. A 15 dB pad shall be provided to accommodate high output microphone signals. A balanced-bridg- ing line input suitable for +4 dBu input signals shall also be provided along with a switch to select either the microphone or line inputs. The voice processor shall have an integral de-esser which shall offer up to 20 db of attenuation within a manually sweepable frequency range of 800 Hz to 8 kHz. There shall be front panel controls for range, frequency, and a bypass switch. The dynamics processing section shall contain an interactive compressor/limiter and downward expander. There shall be front panel controls for compression ratio (1:1 to 10:1), compressor threshold (-50 dBm to +20 dBm), expander threshold (-30 dBm to 0 dBm), and a bypass switch. There shall be a three-band parametric equalizer. Each band shall have ±15 dB maximum boost/cut, and continuously variable bandwidth (.3 octaves to 4 octaves). The equalizer bands shall have substantially overlapping frequency ranges, with a com- bined range of 16 Hz to 22 kHz. There shall be a front panel bypass switch. The voice processor shall be equipped with the following LED displays: An eight-segment LED display shall be provided for monitoring the overall output level, six-segment displays for monitoring the de-esser, compressor/limiter, and downward ex- pander. All displays shall be independent. There shall also be a single LED clip indicator to indicate clipping within either of the input preamplifiers or buffers. The microphone input shall be an active balanced bridging design terminated with 3-pin XLR-female connector (AES/IEC standard wiring). The microphone preamp shall be capable of an equivalent input noise specification of at least -126 dBu (150- Ohm source, 60 dB gain, 20 Hz to 20 kHz). The line input shall be a balanced, transformerless design using a 3-pin XLR-fe- male connector (AES/IEC standard wiring). All input circuitry shall incorporate RFI filters of the LC low-pass type. The output shall be an active balanced design terminated with a 3-pin XLR-male connector (AES/IEC standard wiring). The output signal level shall be switchable to accommodate subsequent line or microphone inputs. The output section shall provide a switchable phase rotator for the purpose of improving the asymmetry of speech waveforms.

  • Page 33: Warranty And Service

    The Symetrix Limited Warranty exceed the price allocatable to the product or any part thereof which gives rise to the claim. In no event will Symetrix be liable Symetrix, Inc. expressly warrants that the product will be free for any incidental or consequential damages including but not from defects in material and workmanship for eighteen (18) limited to damage for loss of revenue, cost of capital, claims months from the date the product is shipped from the factory. of customers for service interruptions or failure to supply, Symetrix's obligations under this warranty will be limited to and costs and expenses incurred in connection with labor, repairing or replacing, at Symetrix's option, the part or parts overhead, transportation, installation or removal of products, of the product which prove defective in material or workman- substitute facilities or supply houses. ship within eighteen (18) months from the date the product is shipped from the factory, provided that the Buyer gives Servicing the 528E Voice Processor Symetrix prompt notice of any defect or failure and satisfactory If you have determined that your 528E Voice Processor proof thereof. Products may be returned by Buyer only after requires repair services and you live outside of the United a Return Authorization number (RA) has been obtained from States please contact your local SymNet dealer or distributor Symetrix. Buyer will prepay all freight charges to return the for instructions on how to obtain service. If you reside in the product to the Symetrix factory. Symetrix reserves the right to U.S. then proceed as follows. inspect any products which may be the subject of any warranty Return authorization claim before repair or replacement is carried out. Symetrix At the Symetrix factory, Symetrix will perform in-warranty or may, at its option, require proof of the original date of purchase out-of-warranty service on any product it has manufactured for (dated copy of original retail dealer's invoice). Final determina-...

  • Page 34: Declaration Of Conformity

    User’s Guide 528E Voice Processor Declaration of Conformity 32/32 Declaration of Conformity We, Symetrix Incorporated, 6408 216th St. SW, Mountlake Terrace, Washington, USA, declare under our sole responsibility that the product: 528E Voice Processor to which this declaration relates, is in conformity with the following standards: EN 60065 Safety requirements for mains operated electronic and related apparatus for household and similar general use. EN 55103-2 Electromagnetic compatibility - Generic immunity standard Part 1: Residential, commercial, and light industry. The technical construction file is maintained at: Symetrix, Inc. 6408 216th St. SW Mountlake Terrace, WA, 98043 USA The authorized representative located within the European Community is: World Marketing Associates P.O. Box 100 St. Austell, Cornwall, PL26 6YU, U.K. Date of issue: March 15, 1999 Place of issue: Lynnwood, Washington, USA Authorized signature: Dane Butcher, President, Symetrix Incorporated.

  • Page 35: Appendix A - Output Level Switch

    User’s Guide 528E Voice Processor Appendix A - Output Level Switch WARNING Lethal voltages are present inside the chassis. Perform all service work with the unit disconnected from all AC power. CAUTION These servicing instructions are for use by qualified personnel only. To avoid electric shock, do not perform any servicing other than that contained in the operating instructions portion of this manual unless you are qualified to do so.
  • Page 36 6408 216th St. SW, Mountlake Terrace, WA, USA • Tel +1 (425) 778-7728 • Fax +1 (425) 778-7727 • Web www.symetrixaudio.com © 2006, Symetrix, Inc. All rights reserved. Printed in the United States of America. Symetrix Part Number 53528E-1C00. The information in this User’s Guide is subject to change without notice. Symetrix, Inc. shall not be liable for technical or editorial errors or omissions contained herein; nor is it liable for incidental or consequential damages resulting from the furnishing, performance, or use of this material. Mention of third-party products is for informational purposes only and constitutes neither an endorsement nor a recommendation. Symetrix assumes no responsibility with regard to the performance or use of these products. Under copyright laws, no part of this User’s Guide may be reproduced or transmitted in any form or by any means, electronic or mechanical, without permission in writing from Symetrix, Inc. If, however, your only means of access is electronic, permission to print one copy is hereby granted. Product names mentioned herein may be trademarks and/or registered trademarks of their respective companies.

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