421m AGC-Leveler
Contents
1. O Symetrix O Symetrix Troubleshooting Chapter 8 No outputsignal Check cables and connections Determine that there really is a signal coming from the source and that it is getting to the 421m Verify cables by patching input and output connections together at the unit Check for AC power presence Check input by plugging headphones halfway into the sidechain jack and listening for input signal this verifies that the unit is receiving signal Check output by plugging headphones into output jack Check downward expander threshold setting it may be too high for the current signal level Stuck in bypass mode Check setting of the STEREO LINK button In single unit mono systems on independently operating units and on master units the switch should be in the IN position Nolimiter action Check the threshold control setting Signal levels may be too low Don t try to calibrate with sine waves Use speech or music Distortion Is the incoming signal already distorted Listen up stream from the 421m or manually place the unit in BYPASS mode to determine that you are feeding it a clean signal Buzzin the output Check input and output connector wiring Check for ground loops between interconnected system equipment Are all system components on the same AC ground Noise hiss Check input signal levels and input level control settings The input may be too low in level If so boost the signal from your2. AUTO DOWNWARD EXPANDER NR THRESHOLD Vu AGC LEVELER RELEASE ACTIVE BYPASS FAST SLOW LOW AUTO RELEASE LEVEL RECOVERY RATE 21 FAST SLOW HIGH C BYPASS RATIO TARGET OUTPUT LEVEL 44 DECREASE INCREASE Y J Z RECOVERY RATE TARGET EXPAND LED LEVELER button OUTPUT LEVEL DOWNWARD EXPANDER ACTIVE LED AGC AUTO RELEASE RATIO control THRESHOLD control control DOWNWARD EXPANDER RELEASE control DOWNWARD EXPANDER THRESHOLD Determines the level below which the downward expander operates which reduces the gain at a 1 2 dB ratio At the max CCW setting of the control the threshold setting is automatic determined by the setting of the AUTO RELEASE control In this case the downward expander acts more like a gate very high ratio NOTE the silence detector thinks that acoustic feedback is silence At the max CW setting the threshold setting is low enough that all signals are above threshold therefore the expander is bypassed DOWNWARD EXPANDER RELEASE Determines the rate of decay for the downward expander EXPAND LED Tells when the downward expander is active LEVELER ACTIVE LED Indicates the leveling activity If the LED is off then the gain of the AGC Leveler is frozen at the last setting The signal level where the gain is frozen is determined by the AUTO RELEASELEVEL control AUTO RELEASE LEVEL Determines the level that the input signal m
3. Telephone 425 787 3222 Fax 425 787 3211 E mail symetrix symetrixaudio com Website www symetrixaudio com son une RE cm we PARTA a As s s AS 7 N ay s AN s E 2 o FMa M M asta E O O e O o OC he o Front panel 421m AGC LEVELER i BALANCED UNBALANCED LINE OUTPUT BALANCED UNBALANCED LINE INPUT BALANCED MICROPHONE INPUT conectou 53 AS MPT fo o i LYNNWOOD WA USA a N li NI EE TENT ae A 3 ae oa MAXIMUM ll Ji 5 as ji p a O power kas O KZ Be o WY 2 AR OE sou esa auy e u pan sveno me Lumon wsmoron T ES SS D EEE TEMEA SOE Rear panel OSymetrix O Symetrix Operator Safety Summary Equipment Markings CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN TO REDUCE THE RISK OF FIRE OR WARNING ELECTRIC SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE a RISQUE DE CHOC ELECTRIQUE AVIS NE PAS OUVRIR SEE OWNERS MANUAL VOIR CAHIER D INSTRUCTIONS No user serviceable parts inside Refer servicing to qualified service personnel ll ne se trouve a l interieur aucune piece pourvant entre repar e l usager S adresser a un reparateur comp tent The lightning flash with arrowhead symbol within an equilateral triangle is intended to alert the user of the presence of uninsulated dangerous voltage within the product s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons The exclamation point wi
4. Operation Chapter 5 Initial Setup Set the front panel controls as follows DOWNWARDEXPANDER THRESHOLD Bypass DOWNWARDEXPANDER RELEASE Straight up AGC LEVELER AUTO RELEASELEVEL Straight up RECOVERY RATE In RATIO 4 1 TARGET OUTPUT Straight up SPEECH CURVE 125 Hz Out SPEECHCURVE 6kHz Out Apply an input signal to the 421m Observe the input and output meters there should be activity The input meter reads the actual input signal The output meter reads the actual output signal Both meters are peak responding and are calibrated in VU 0 VU 4 dBu 1 23V RMS Set the AGC Leveler by first adjusting the TARGET OUTPUT LEVEL control for the output level required Next decrease the setting of the RATIO control until you obtain the desired amount of dynamic range reduction Speech tolerates higher ratios than music Use a higher ratio 4 1 for stronger leveling action The difference between the two meters shows what the 421m is doing Re member that a 1 1 ratio setting amounts to BYPASS for the AGC Leveler Set the RECOVERY RATE button as required by the program material starting point FAST speech SLOW music SLOW speech and music In sound reinforcement applications set the AUTO RELEASE LEVEL control to limit the pickup range of the microphone Lower more CCW settings will increase the pickup range the level setting is lower therefore the AGC Leveler will track lower level signals and higher settings will force the u
5. Release Time Program dependant 0 3 3 5 seconds depending on amount and duration Specifications Mic Preamp Gain Range 15 dB to 45 dB Impedance 10k Ohms Max Input Level 8 dBu THD Noise gain control fully clockwise 85 dBu Phantom Power 48V 2 CMRR gt 80 dB 10 Hz 20 kHz Sonics Frequency Response 20 to 50 kHz 4 dBm 0 1 dB 0 3 dB mic Harmonic Distortion lt 0 05 20 Hz to 20 kHz 4 dBm 30 kHz bandwidth Typically lt 0 01 1000 Hz 90 dBu 20 kHz noise bandwidth rms responding meter Residual Noise Speech Curve Type Switch selected cutoff filters allow tailoring LF and or HF response for speech applications Frequencies LF 125 Hz 12 dB octave HF 6 kHz 24 dB octave ene to at Input Output Metering Auto Release Threshold 70 dBu to 30 dBu WPS me de Attack Time approximately 1 ms Ralie Peak Release Time Program dependant 500 ms 5 seconds ihrati OIL E depending on amount and duration Calibration 0 dB 0VU 4 dBm 1 23V Physical Marae Output ou Size hwo 1 72x 19x 6 25 inches ii Ratio 10 1 4 37 x 48 26 x 15 875 centimeters Shipping Weight 8 Ibs 3 63kg net Threshold 15VU to 23VU bypass Attack Time 1 ms for 90 gain reduction Electrical Release Time 0 8 seconds Connector EC 3 pole Power Requirements 117V nominal 107 to 125V AC 50 to 60 Hz 10 watts 220V AC 50 Hz 10 watts Note The maximum operating ambient temperature is 25 degrees C 421m Architects and Engineers Speci
6. 6kHz spas O NO OOO O O OINPUTLEVEL 54 48 42 36 30 24 18 12 6 OVU 6 12 STEREOLINK BYPASS E AW 7 am IN IN MASTER IN 8 15 dE BYPASS dE BYPASS dE SLAVE E BYPASS LMT ey 54 48 42 36 30 24 18 12 6 OVU 6 12 CLIP 6 a BYPASS So SO Coe OUTPUT LEVEL O o i _ OUTPUT LIMITER ae filters BYPASS button INPUT LED meter THRESHOLD LED 125 Hz high pass 6kHz low pass OUTPUT LIMITER THRESHOLD control STEREO LINK button OUTPUT LED meter OUTPUT LIMITER THRESHOLD LED Indicates peak limiting activity OUTPUT LIMITER THRESHOLD Sets the threshold of the peak ceiling limiter This works in conjunction with the leveler s ratio and target output level controls The 421m will not allow the peak limiter to be set higher than the setting of the target output level control If you think about it it would make no sense if you allowed peaks past the target output level SPEECH CURVE FILTERS The high pass filter button on the left has a 12 dB octave rolloff and the low pass filter button on the right rolls off at 24 dB octave STEREO LINK Sets the master slave relationship between 2 units The normal setting is IN BYPASS BUTTON This control hard wire bypasses the 42 Im If STEREO LINKED all linked slave units revert to bypass when the bypass button on the master unit is out On any individual slave unit that has been STEREO LINKED STEREO LINK button OUT this button
7. any third party including any dealer or sales representative to assume any liability or make any additional warranties or representation regarding this product information on behalf of Symetrix This limited warranty gives the buyer certain rights You may have additional rights provided by applicable law Limitation of Liability The total liability of Symetrix on any claim whether in contract tort including negligence or otherwise arising out of connected with or resulting from the manufacture sale delivery resale repair replacement or use of any product will not exceed the price allocatable to the product or any part thereof which gives rise to the claim In no event will Symetrix be liable for any incidental or consequential damages including but not limited to damage for loss of revenue cost of capital claims of customers for service interruptions or failure to supply and costs and expenses incurred in connection with labor overhead transportation installation or removal of products substitute facilities or supply houses 5s Symetrix O Symetrix Servicing the 421m If you have determined that your 421m requires repair services and you live outside of the United States please contact your local Symetrix dealer or distributor for instructions on how to obtain service If you reside in the U S then proceed as follows Returnauthorization At the Symetrix factory Symetrix will perform in warranty or out o
8. mike Every user has their own idea of how to use the mike You can fight them and win with the 421m AGC Leveler Secondary Sound System Feeds Many sound systems derive secondary feeds for ancillary systems that serve related areas of a facility In arenas or large stadiums this might be the outer concourses PA shadow zones conces sion areas rest rooms dressing rooms etc In a church it might be the lobby or cry room In a TV studio it could be the IFB interrupted foldback system 1 Symetrix O Symetrix Tape Duplication Anytime you change recording media especially between a professional format and a consumer format how about DAT to consumer cassette patch a 421m into the recording chain to perform a gentle squeeze to match the signal level to the input of the next device and peak limiting Try 2 1 RATIO set the TARGET OUTPUT LEVEL control for the average level that you need and use the limiter to control the peaks Many churches record the Pastor s message sermon and make it available on tape by the end of the service Considering the speed with which this must occur a 421m might be just the thing to keep the average levels hot while still preventing overload Teleconferencing Many teleconference users want to record the content of the conference Of course audio levels are all over the map one participant shouts another is timid Try a 421m between the audio mixer and one track of the tape machine
9. operation the correct valueis0 125A 250V AC standard Operating Location Donotoperate this equip mentunder any ofthe following conditions explosive atmospheres in wet locations in inclement weather improper or unknown AC mains voltage or ifimproperly fused Do not install near any heat source such as radiators heat registers stoves or other apparatus including amplifiers that produce heat Unplug this apparatus during lightning storms or when unused for long periods of time Stay Out of the Box To avoid personal injury or worse do not remove the product covers or panels Do not operate the product without the covers and panels properly installed Only use accessories specified by the manufacturer Clean only with a damp cloth User serviceable parts There are no user serviceable parts inside the 421m In case of failure refer all servicing to the factory Servicing is required when the 421m has been damaged in any way such as when a power supply cord or plug is damaged liquid has been spilled or objects have fallen into the apparatus the apparatus has been exposed to rain or moisture does not operate normally or has been dropped Chapter 3 Front amp Rear Panel Overview This chapter provides a basic overview of the 421m by describing the input and output connec tions power connection operating controls and front panel LED indicators Front panel view left O 421m i AGC LEVELER a EXPAND
10. option require proof of the original date of purchase dated copy of original retail dealer s invoice Final determination of warranty coverage lies solely with Symetrix Products repaired under warranty will be returned freight prepaid via United Parcel Service by Symetrix to any location within the Continental United States Outside the Continental United States products will be returned freight collect The foregoing warranties are in lieu of all other warranties whether oral written express implied or statutory Symetrix Inc expressly disclaims any IMPLIED warranties including fitness for a particular purpose or merchantability Symetrix s warranty obligation and buyer s remedies hereun der are SOLELY and exclusively as stated herein This Symetrix product is designed and manufactured for use in professional and studio audio systems and is not intended for other usage With respect to products purchased by consumers for personal family or household use Symetrix expressly disclaims all implied warranties including but not limited to warranties of merchantability and fitness for a particular purpose This limited warranty with all terms conditions and disclaimers set forth herein shall extend to the original purchaser and anyone who purchases the product within the specified warranty period Warranty Registration must be completed and mailed to Symetrix within thirty 30 days of the date of purchase Symetrix does not authorize
11. using the AUTO setting of the downward expander first set the AUTO RELEASE LEVEL control in the AGC Leveler section Then use the expander s RE LEASE control to prevent expander action during short pauses General PA System Considerations In a public address system it is important to ensure that feedback cannot occur when the AGC Leveler reaches a state of maximum gain for instance when the 421m is trying to boost the volume of a very quiet voice Avoid this by talking into the mic just loud enough for the ACTIVE LED to light If you hear feedback then raise the AUTO RELEASE LEVEL until the feedback dies Lower ing the RATIO will also help Remember The ACTIVE LED does not have to be on constantly while signal is present In fact depending on your circumstances you may elect to set the AUTO RELEASELEVEL high enough to prevent the 421m from responding to all soft voices Stereo Link And Bypass Switching The STEREO LINK and BYPASS buttons interact In stereo mode the designated master unit takes over all functions for both units including in bypass switching If the STEREO LINK button is in the out position the 421m is in slave mode which means the 421m gets its commands via the link cable from the master unit Note Ifa421mis placed in SLAVE mode and is not connected to another 421m via a linking cable the unit will remain in BYPASS mode regardless of the setting of its BYPASS button If there is a master unit connected then th
12. with a properly grounded outlet Do not defeat the purpose ofthe grounding plug Mounting In An Equipment Rack The 421m occupies one rack space 1U in a standard equipment rack with a width of 19 48 3cm a depth of 6 5 16 8cm and a height of 1 75 4 45cm Allow at least 4 10 16cm behind the unit for the protrusion of connectors We recommend you take care not to mount the 421m next to devices that emit large electromagnetic fields such as audio power amplifiers To do so may compromise the noise performance of the 421m The 421m has been designed to conform to mechanical guidelines as described in EIA Standard RS 310 C and IEC Recommendation 297 Audio Input Connections The 421m s line input connections are via a standard 14 phone jack and barrier terminals The 421m s microphone input connection is an XLR female For optimum system performance we recommend that the 421m be connected to balanced signals If this is not practical in your situa tion then you may connect to unbalanced sources Audio Output Connections The 421m s audio output connections are via standard male XLR jack 14 phone jack and barrier terminals located on the rear panel For optimum system performance we recommend that the 421m be connected to balanced devices If this is not practical in your situation then you may connect to unbalanced devices Use any combination of the input and output connections All of the input connections are paralleled The
13. 421m AGC Leveler User s Guide O Symetrix Table of Contents Chapter 1 Introduction l Chapter 2 Operator Safety Summary Chapter 3 Front amp Rear Panel Overview Chapter 4 Installation O ON N Chapter 5 Operation Chapter 6 Applications 10 Chapter 7 Specifications 13 Chapter 8 Troubleshooting 14 Chapter 9 Warranty and Service 15 Rev B 00 18 February 1999 Symetrix part number 53421M0B00 Subject to change at without notice 1999 Symetrix Inc All right reserved Symetrix is a registered trademark of Symetrix Inc 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 QD et Under copyright laws no part of this manual may be rix 14926 35th Ave West Lynnwood WA 98037 USA reproduced or transmitted in any form or by any means electronic or mechanical including photocopying scanning recording or by any information storage and Tel 425 787 3222 retrieval system without permission in writing from Fax 425 Far Seul Symetrix Inc Email symetrix symetrixaudio com O Symetrix i Chapter 1 Introduction The Symetrix 421m is a wide range AGC Leveler a peak limiter and adownward expander that features a microphone preamp eliminating the need for a separate outboard microphone preamp in some applications The 421m reduces the dyna
14. XLR output connector and the balanced screw terminal outputs are paralleled The unbalanced output is paralleled from the screw terminal output The 421 wants line level signals such as those found at the output of a CD player cassette machine mixer output mixer channel insert jack etc Stereo Interconnect To stereo link two 421m s interconnect the STEREO LINK jacks found on the rear panels of the units using a five pin DIN male to DIN male patch cord Symetrix p n 037010 This looks like a MIDI cable and a MIDI cable may actually work if all five pins are actually connected to each other Note Although the stereo interconnect cable looks like a MIDI cable it isn t There is nothing remotely resembling MIDI inside or between two 421m s If you connect either connector to a MIDI device it probably won t harm anything but it definitely won t work Decide which unit is the master and which unit is the slave using force only if absolutely neces sary and set the front panel MASTER SLAVE switches accordingly In stereo mode the slave unit s controls are disabled and only the master unit controls affect operation The following diagram shows how to stereo link two 421m s Note If there is no master unit connected via the Stereo Link connectors the slave unit any unit with it s MASTER SLAVE switch in the OUT position remains in bypass mode regardless of the setting of its bypass switch 7 Symetrix O Symetrix
15. a wall socket carefully read the information in the following chapter AC Line Connection A sticker on the right end of the unit as viewed from the front indicates the nominal voltage setting for the unit as it left the Symetrix factory If this does not correspond to the voltage setting for your locale then do not attempt to apply power to the 421m Instead return the unit to your local Symetrix distributor for modification orreplacement The 421m is shipped from the Symetrix factory with a detachable AC power cable IEC standard included Depending on the intended destination the power plug is either the US type intended for 115VAC use or the Europlug type If the power cable s plug is not right for your locale then please contact your local Symetrix distributor for the proper cable Once you have determined that the 421m s operating voltage matches that of your locale and you are ready to begin follow these steps 1 Plug the socket end of the power cable into the recessed AC power receptacle on the back of the 421m 2 Plug the other end of the power cable into a three hole grounded outlet or power strip Warning The421misintended to be electrically grounded It has been provided with a three wire grounding plug a plug that has a third grounding pin This plug will fit only agrounded AC outlet This is a safety feature Ifyou are unable to insert the plug into the outlet contact a licensed electrician to replace the outlet
16. and another between the telephone interface and another track of the tape machine Using separate 421m s and separate tape tracks will help if and when someone tries to transcribe the conference Keeping things separate also helps negate the 421m s tendency to bring the telephone interface s leakage trans hybrid loss up to the same level as the caller which isn t a good idea The 421m helps by keeping the signal levels more consistent from caller to caller which is a good idea Theatre and Auditorium Cue Systems An auditorium cue system consists of a microphone s mounted in the audience area of a theatre or auditorium that feeds an amplifier that drives speakers located in the backstage areas of the hall The potential dynamic range in this application is tremendous ranging from an empty room to an audience on their feet making a plea for an encore A 421m in conjunction with close miking of the person calling the cues can work wonders keeping this sort of system under control keeping the level high enough to be audible and low enough to not be annoying The downward expander can reduce the level when the room is very quiet to eliminate electronic noise yet open up if someone speaks Post Production A 421m can be invaluable in post production How about Use the 421m when transferring location sound tapes If you keep the ratio low you ll gain consistency with a minimum loss of dynamic range Use multiple 421m s to keep vari
17. ave to charge you Of course if the problem turns out to be operator inflicted you ll have to pay for both parts and labor In any event if there are charges for the repair you will pay for the return freight All charges will be COD unless you have made other arrangements prepaid Visa or Mastercard Out of Warranty Repairs If the warranty period has passed you ll be billed for all necessary parts labor packaging materi als and freight charges Please remember you must call for an RA number before sending the unit toSymetrix 16 O Symetrix O Symetrix Symetrix Inc 14926 35th Ave West Lynnwood WA 98037 2303 USA Tel 425 787 3222 Fax 425 787 3211 Website http www symetrixaudio com Email symetrix symetrixaudio com
18. aying rhythm and too loud when playing leads A 421m can help you out Connect the 421m into the mixer s channel insert jack use a relatively low RATIO setting use the expander if you need to Remember that lower ratio settings allow for more dynamics than the higher settings which means more difference between soft and loud This trick also works on microphones that are sung into and used for announcements The 421m keeps the announcements audible without the worry of forgetting to bring the fader down during a song Again use a low RATIO setting around 2 1 If you try this on a submix be careful because the large number of microphones involved makes it that much easier to push the sound system into feedback Mixdown You can use the 421m during mixdown for a number of different things For voiceover s let the 421m ride the level of the announcer while you set the basic announcer to music bed ratio or let the 421m ride the music bed while you ride the announcer s level Process background vocals with the 421m It will keep them consistently hot without making them sound squashed unless that s what you want Try using the 421m on individual instruments as a way of keeping their level more consistent without radically altering their timbre Paging Systems Just like the poor lectern mike paging systems suffer from the same ills It really doesn t matter if the audio begins life in a telephone system or if you have a dedicated paging
19. console or input source Is the input signal already noisy Listen up stream from the 421m to determine if you are feeding it a clean signal The 421m doesn t power up or doesn t respond properly Consult a qualified service technician or the Symetrix factory Note Repeated fuse blowing is a sure sign of electronic distress Unplug the unit and make arrangements for repair Warning The fuse is located internally and lethal voltages are present inside the chassis The fuse is not considered user serviceable If the fuse is blown the 421m probably needs repair 14 Chapter 9 Warranty amp Service 421m Limited Warranty Symetrix Inc expressly warrants that the product will be free from defects in material and workman ship for one 1 year Symetrix s obligations under this warranty will be limited to repairing or replacing at Symetrix s option the part or parts of the product which prove defective in material or workmanship within one 1 year from date of purchase provided that the Buyer gives Symetrix prompt notice of any defect or failure and satisfactory proof thereof Products may be returned by Buyer only after a Return Authorization number RA has been obtained from Symetrix Buyer will prepay all freight charges to return the product to the Symetrix factory Symetrix reserves the right to inspect any products which may be the subject of any warranty claim before repair or replace ment is granted Symetrix may at its
20. e BYPASS button on the master determines the status of the slave E gt Symetrix O Symetrix Applications Chapter 6 An AGC Leveler has many applications in recording studios auditoriums or theatres commercial or industrial PA systems tape duplication systems and broadcast Here follows a small sample of applications Broadcast Telephone Line Driver At sometime or another every broadcast engineer ends up having to send audio down a telephone line Of course you need to keep levels hot but if you hit the line too hard the phone company frowns It s good practice to ensure that there is a hard limit to any signal that ends up going down a phone line The 421m is well suited to the task of unobtrusive yet unyielding control of audio levels As a starting point use the SLOW recovery rate low RATIO 2 1 and a low AUTO RELEASE LEVEL Set the TARGET LEVEL control for the desired average level into the line and then dial in enough peak limiting to keep the peaks under control You may want to back the TARGET LEVEL off slightly so that you don t need as much peak limiting Peak limiters are more inaudible if you only limit occasional peaks Conference or Courtroom Recording If you re recording conferences or courtroom proceedings you are faced with the same problem at the lectern microphone i e some people speak too softly while others are too loud If possible install a separate 421m on each microphone and feed the outputs o
21. e it has a chance to grow into something potentially damaging Set the OUTPUT LIMITER by adjusting the THRESHOLD control either for the absolute maximum output level desired as read on the threshold control s panel scale or as indicated on the peak re sponding output meter Set the SPEECH CURVE buttons as necessary and as required by the situation The 125Hz button removes boominess and some of the proximity effect caused by close talking a single D cardioid microphone such as a Shure SM 58 without making voices sound thin The 6kHz button removes sibilance and high frequency feedback without causing telephone voice Note Do not use pink noise or sine waves for setup It simply will not work the ARM circuitry will think your signal is noise Use speech or music Helpful Hints Microphone Techniques Note The ability of the expander to discriminate between wanted and unwanted signals is partially determined by mic technique Be particularly careful of high frequency sounds entering the side or rear pattern of a cardioid mic Most cardioid mics exhibit a sharply rising off axis response charac teristic at higher frequencies Check the off axis curves in the manufacturer s literature If there s only a 3dB 6dB difference between the on axis frontal response and the off axis side or rear re sponse in the 5kHz to 10 kHz region high frequency sounds will be picked up by the mic thereby possibly preventing the downward expand
22. elecommunications and Title V deals with miscellaneous issues Of particular interest to sound system providers or installers is Title III which says that many of the places where you find sound systems must provide assisted listening devices for persons with sensory impairment Some of the solutions employed are headphone jacks at certain seats low powered AM or FM transmitters broadcasting to Walkman R type radios or to facility supplied radios and infrared transmission systems Regardless of the transmission method these systems all require a signal of reduced dynamic range so that the users can hear both the softest and loudest parts of a performance The 421m is ideally suited to this application Try moderate to high ratios 2 1 and up and long release times Pick an AUTO RELEASE level that keeps the AGC action somewhat unobtrusive Use the peak limiter to keep the transmitter out of clipping 10 Lectern Mounted Microphones A common and thoroughly vexing problem is that of the ubiquitous lectern microphone A staple of hotels public meeting places courtrooms and churches the podium microphone gets used and misused by one and all Anyone who uses a microphone has their own idea of how and where to place the microphone relative to their lips of course and how they should speak into it Some get their cues from TV which any self respecting audio person knows is usually wrong and some just make it up as they go Some stick the
23. er from reducing unwanted sounds Use the mic s directional pattern to keep unwanted sources as far off axis as possible Do every thing you can to discriminate against unwanted sounds through good mic technique The sounds picked up by an individual mic must be primarily the sound of the desired signal or the 421m s downward expander won t be able to discriminate between signal and noise Optimizing Control Settings When searching for optimum control settings here are a few rules to follow AGC LEVELER The FAST setting of the RECOVERY RATE button is best suited for speech sig nals Use the SLOW setting for musical or noisy signals or if you want the gain changes to be as unobtrusive as possible The RATIO control determines how much of the input signal s dynamic range makes it to the out put We recommend starting at 4 1 so you can clearly hear the effect and then reduce the ratio if necessary AUTO RELEASELEVEL ARL This control determines the signal level needed to cause gain re lease in the AGC Leveler A suggested method of setting it is with no signal present increase the setting of the ARL control until the green ACTIVE LED extinguishes Then further increase the control setting slightly For musical signals use the SLOW setting of the RECOVERY RATE button Set the AUTO RE LEASELEVEL control so that the ACTIVE LED is extinguished during low level musical passages fade outs or moments of silence DOWNWARD EXPANDER When
24. f the 421m s into the line inputs of your mixer If separate 421m s for each mic are not an option then place a single 421m between the mixer output and the input of the tape recorder Foreground Music The CD changer has propelled canned music into a new era The problem of course is the wide dynamic range of CD s coupled with the fact that different CD s as mastered at diverse and unpre dictable levels Most CD s simply have too much range for foreground or background music applications The 421m helps reduce the overall dynamic range while retaining some semblance of the music s original dynamics You can link two units together for stereo if desired There s probably no need to use the downward expander in this application so turn the THRESH OLD control to the BYPASS position Set the AGC Leveler RATIO to 2 1 and use the SLOW recovery rate setting Set the AUTO RELEASE LEVEL to 9 00 o clock or lower Experiment with the PEAK LIMITER threshold and use the PEAK LIMITER only if necessary Americans with Disabilities Act The American Disabilities Act ADA of 1990 Public Law 101 336 affects any of us who supply equipment to or operate public gathering places There are five major aspects Titles to this law all of which have staged implementation dates Title I deals with employment issues Title II deals with public services Title III deals with public accommodations and services operated by private entities Title IV deals with t
25. f warranty service on any product it has manufactured for a period of five years from date of manufacture Before sending anything to Symetrix please contact our Customer Service Department for a Return Authorization RA number The telephone number is 425 787 3222 Monday through Friday 8AM 800 hours through 4 30 PM 1630 hours Pacific Time In Warranty Repairs To get your 421m repaired under the terms of the warranty 1 Call us for an RA number 2 Pack the unit in its original packaging materials 3 Include your name address daytime telephone number and a brief statement of the problem 4 Write the RA number on the outside of the box 5 Ship the unit to Symetrix freight prepaid We do not accept freight collect shipments Just do these five things and repairs made in warranty will only cost you one way freight charges only We ll pay the return surface freight If you choose to send us your product in some sort of flimsy packaging we ll have to charge you for proper shipping materials If you don t have the factory packaging materials then do yourself a favor by using an oversize carton wrap the unit in a plastic bag surround it with bubble wrap and place it in the box surrounded by Styrofoam peanuts Be sure there is enough clearance in the box to protect the rack ears you wouldn t believe how many units are returned with bent ears We won t return the unit in anything but Symetrix packaging for which we will h
26. fications The Automatic Gain Control AGC shall be a single channel model that reduces the dynamic range of wide range wideband audio signals providing peak limiting downward expansion and bandpass limiting filters The AGC shall occupy one rack space 1U The AGC shall be capable of controlling audio signals ranging from 70 dBu to 24 dBu and reducing their range by an input output ratio ranging from 1 1 to 4 1 The input output ratio shall be adjustable via a front panel control Fast slow response speed switching shall be provided to accommodate speech and music sources A target output level control shall be provided to shift the level of the output signal over a nominal 20 dB range The release time of the AGC shall be controlled by the presence of input signal and the signal sensor shall be capable of discriminating between music speech and random noise or pure tones The threshold level of the signal sensor shall be adjustable via a front panel control and the presence of signals above the threshold setting shall be indicated via a green LED The AGC shall also contain an integral peak limiter having at least a 10 1 ratio and adjustable threshold level A green LED indicator shall be provided to indicate peak limiter activity The peak limiter threshold shall determine the absolute maximum output amplitude of the AGC Leveler regardless of other conditions The AGC shall also contain an integral downward expander having a 1 2 expansion ratio with
27. has no effect INPUT LED This meter indicates the input signal level to the 421m It is a VU calibrated peak reading meter OUTPUT LED This meter indicates the output signal level of the 421m Itis a VU calibrated peak reading meter Rear panel view left BALANCED UNBALANCED LINE OUTPUT O 421m AGC LEVELER 6 Symetrix es ENS eu a ees connect To 20 WATTS MAXIMUM a POWER q FABRIQU AUX E U PAR SYMETRIX INC LYNNWOOD WASHINGTON REFEREZ TOUTE R PARATION UN TECHNICIEN QUALIFI SIG EARTH GND GND EE SYMETRIX 421 ONLY NOT A MIDI CONNECTOR SERIAL NUMBER AC INPUT connector STEREO LINK connector OUTPUT connectors AC INPUT This connector accepts nominal AC power sources of 115 volts or 230 volts see Appendix A Specifications for voltage tolerance ranges See chapter 4 Installation for details on the detachable IEC power cable SERIAL NUMBER Write this down in a safe place how about the front of this user s guide While you re at it do us a favor and return your completed warranty card Not only does it establish your warranty it helps give us a clue to your future equipment wants needs and desires STEREO LINK This 5 pin DIN female connector is used to link two 42 Ims for stereo operation Referto the STEREO INTERCONNECT section on page 6 for additional information OUTPUT CONNECTORS These are electro
28. istortion and the balanced outputs shall be capable of delivering 23 dBm into a 600 ohm load The mic level input shall accommodate 8dBu signals There shall be separate gain trim controls for the mic and the line inputs and the mic input shall provide 48v phantom power Overall frequency response shall be 20 Hz to 20 kHz 1dB measured at 4 dBm output There shall be no more than 0 02 harmonic distortion measured under the following conditions 4 dbu input 4 dBm output BYPASS switch out 1000 Hz Residual noise output shall be no greater than 90 dBm measured with a 20 kHz noise bandwidth When the unit is inoperative either by loss of power or viathe BYPASS switch the inputs and outputs shall be wired together There shall be no transients transmitted to the output terminals during either turn on turn off or bypass operation unless something upstream generates transients Access to the AGC s sidechain shall be provided via a single 4 TRS female connector The ring connection shall be the sidechain output and the tip connection shall be the sidechain return The AGC shall be capable of operating by means of its own built in power supply connected to 115V nominal ac 105 to 130V 50 60 Hz 230V nominal 210 to 260V ac 50 Hz where applicable The AGC shall be listed by Underwriters Laboratories Inc UL or other equivalent nationally recognized safety testing agency The unit shall be a Symetrix Incorporated model 421m AGC Leveler
29. mic range of its input signal by the amount of its ratio setting That is if the ratio setting is 2 1 then 40 dB of input range turns into 20 dB at the output A fast peak limiter puts an absolute ceiling on the output level so you know that peaks are held to the level that you set A downward expander reduces the gain when signal levels fall too low to process reducing the noise buildup at low signal levels Speech filters allow a reduction of reduction the bandpass of the 421m to minimize feedback or amplifier power waste caused by spurious out of band signals AGC Levelers can be used anywhere that you might need to reduce the dynamic range of an audio signal over a wide range of signal levels Possible applications include tape duplication especially cassette driving telephone lines driving broadcast or STL transmitters podium or lectern micro phones paging systems unattended sound systems and music recording The 421m is listed by Underwriters Laboratories Inc UL Samples of this product have been evaluated by UL and meet the applicable UL Standards for Safety We recommend that you read this manual from cover to cover Somewhere between the confines of the two covers you should find the answers to most of your questions If not please feel free to contact our Customer Service department via phone fax or e mail for answers to your questions The numbers are
30. mike near their navel just like on TV or is it that TV news types have their vocal chords somewhere new and others try to use it for a snack You get the idea What this means to you is roller coaster audio levels Try the 421m It will do for a lectern or other announce microphones what no compressor has ever done before consistent audio levels with increased freedom from feedback Some hints use moderate ratios 3 1 to 4 1 unless you want a really in your face sound Use either or both of the speech filter switches The AUTO RELEASE LEVEL affects the size of the microphone s pickup circle More CCW settings expand the circle allowing the 421m to raise lower level voices more remember it won t keep them from sounding distant or off mike Higher settings restrict the pickup range of the microphone so a weak talker won t be picked up as well unless they move in on the microphone to cause the gain to readjust to their voice level In noisy environments try a higher more clockwise setting You can use the downward expander in AUTO mode to gate the mike off when idle Ensure that the TARGET OUTPUT LEVEL isn t high enough to cause feedback when the AGC Leveler has fully engaged you can force a release by quickly turning the AUTO RELEASE LEVEL control and then returning it to its former setting Live PA Have you ever mixed live sound for someone who just can t play at the right level They re usually too soft when pl
31. nically balanced line level low impedance outputs XLR pin 1 is ground pin 2 is high and pin 3 is low The 14 connector tip is high ring is low and sleeve is ground The screw terminal output is wired in parallel to the 14 and XLR connectors Rear panel view right TYPICAL BALANCED UNBALANCED LINE INPUT BALANCED MICROPHONE INPUT CONNECTIONS 63 Es PHANTOM XLR _ PHONE _ SIGNAL EARTH SIG LEVEL LEVEL POWER PIN17 SLEEVE 7 GROUND GND GND TRIM TRIM 48V XLR PHONE SIGNAL PIN27 TIP HIGH XLR PHONE SIGNAL PINS RING LOW IBB G KW 2 o a MIC INPUT connector LINE INPUT connectors PHANTOM POWER button LINE INPUT LEVEL TRIM MIC LEVEL TRIM LINE INPUT These connectors are electronically balanced line level bridging inputs The 4 connector tip is high ring is low and sleeve is ground The screw terminal input is wired in parallel to the 14 connector MICROPHONE INPUT This connector is a balanced low impedance input The female XLR pin 2 is high pin 3 is low and pin 1 is ground MIC LEVEL TRIM Adjusts the gain of the microphone preamp from a minimum of 25dB to a maximum of 50dB PHANTOM POWER Applies or removes microphone phantom power at the MICROPHONE INPUT connector s Symetrix O Symetrix Installation Chapter 4 Before you plug the 421m into
32. ous mix elements audible Try one on FX or Foley and on dialog If you re creating something that will be heard in a specific environment consider using a 421m to preprocess your mix for that environment For instance suppose you re making a point of purchase video that will heard in a noisy department store over a semi ordinary television set With your mixer or an outboard EQ give the dialog a good dose of 2 5k to 5k presence boost to make it cut through the noise Then process the overall mix through the 421m with a 3 1 ratio This will keep the overall level hot but consistent and the combination of presence boosting and overall level control will make your product audible in spite of the adverse environment in which it is represented Be sure to check the previous section entitled Mixdown for additional tips and hints Chapter 7 421m Specifications Connectors Line Inputs 14 TRS jack and screw terminals 20k Balanced Bridging Mic Input XLR female 10k Balanced Bridging Outputs XLR male screw terminals 200 Ohm Source Impedance Differentially Balanced 23 dBm maximum level TS phone Unbalanced 18 dBm maximum level Bypass Relay controlled hard wire bypass in power off and bypass conditions Sidechain TRS phone Unbalanced Send and Receive 1000 Ohm Source Impedance 10k Input Impedance Tip Receive Ring Send Downward Expander Ratio 1 2 Threshold 50VU bypass to 20VU Auto Threshold Attack Time ims
33. ser to be more on mike In recording broadcast or tape duplication applications the AUTO RELEASE LEVEL control sets the minimum signal level that the AGC Leveler will track If the input signal is music with a long fade the AGC Leveler interprets the fade as a decrease in signal level and raises the gain to try to maintain the level set by the TARGET OUTPUT LEVEL control In effect the AGC Leveler un does the fade which may or may not be allowable The AUTO RELEASE LEVEL control sets how far the signal level can fall before the AGC Leveler stops trying to raise the gain More CCW set tings lower this level which may be what you want if you re trying to recreate the long piano chord heard at the end of the Beatles song A Day In The Life Set the downward expander during program pauses to minimize noise buildup by adjusting the Threshold control until the expand activity LED illuminates Set the RELEASE control for the de sired release rate Use the AUTO position of the DOWNWARD EXPANDER THRESHOLD control for situations where the input signal is noisy hum hiss or feedback In AUTO mode the expander tracks the AGC Leveler s internal auto release monitor When the AGC Leveler releases the expander begins working at the rate set by the RELEASE control If the input signal contains acoustic feedback and nothing else above the auto release hold the auto release monitor ignores it which effectively stops the feedback befor
34. thin an equilateral triangle is intended to alert the user of the presence of important operating and maintenance servicing instructions in the literature accompanying the product i e this manual Caution To prevent electric shock do not use the polarized plug supplied with the unit with any extension cord receptacle or other outlet unless the blades can be fully inserted Terms Several notational conventions are used in this manual Some paragraphs may use Note Caution or Warning as a heading Certain typefaces and capitalization are used to identify certain words These are Note Identifies information that needs extra emphasis A Note generally supplies extra information to help you to better use the 421m Caution Identifies information that if not heeded may cause damage to the 421m or other equipment in your system Identifies information that if ignored may be hazardous to your health or that of others Controls switches or other markings on the 421m s chassis Warning CAPITALS Boldface Strong emphasis Important Safety Instructions Please read and keep these instructions Heed and follow all warnings and instructions Install in accordance with the manufacturer s instructions Power Source This product is intended to operate from a power source that does not apply more than 250V rms between the power supply conductors or between either power supply conductor and ground A protecti
35. threshold and release time controls Furthermore the downward expander shall be capable of operating automatically via the signal sensor circuitry A green LED indicator shall be provided to indicate downward expander circuit activity Bandpass limiting filters shall be provided having a lowpass characteristic of 24 dB octave at 6 kHz and a highpass characteristic of 12 dB octave at 125 Hz Both filters shall be capable of being used individually or simultaneously The AGC shall provide identical peak responding input and output level meters These meters shall be capable of responding to signals ranging from 54 VU to 12 VU 50 dBu to 16 dBu An output clipping indicator shall be provided The AGC shall provide facilities for stereo coupling two units via a shielded 5 pin DIN male to male cable A front panel switch shall designate which unit is the master and which unitis the slave The line level inputs shall be active balanced bridging designs terminated with 4 TRS female and screw terminals The mic level input shall also be an active balanced bridging design using a three pin XLR female AES IEC standard wiring The input circuitry shall incorporate RFI filters The outputs shall be active balanced designs having equal source impedances and terminated with 3 pin XLR AES IEC standard wiring and screw terminals A separate 14 TRS jack shall provide an unbalanced output The balanced line level inputs shall accommodate 24 dBu signals without d
36. ust exceed to allow the AGC Leveler to respond If the signal level is below this threshold active LED OFF then the AGC gain is frozen and the AGC allows the signal level to fall to zero This keeps the AGC Leveler from undoing fades etc Another way to understand this control is to think of it in terms of the minimum signal level required to make the AGC Leveler try to maintain the Target Output Level Once the signal falls below the AUTO RELEASE setting the AGC Leveler allows the signal to decrease When the input signal exceeds the AUTO RELEASE setting the AGC Leveler once again tries to maintain constant output level RECOVERY RATE Sets the basic recovery time Fast for speech slow for music or music speech Fast might work for music in special applications RATIO Determines the input output ratio This control instructs the 421m how aggressively you want to maintain the target output level Using a 2 1 ratio a 2dB drop in the input level results in a 1dB drop at the 421m s output With a 4 1 ratio a 4dB drop at the input is limited to a 1dB decrease at the output The 421m computes the additional make up gain needed for the ratio setting and applies it to the VCA so that the output level doesn t change with the setting of the ratio control TARGET LEVEL Sets the desired output level gt Symetrix O Symetrix Front panel view right OUTPUT LIMITER SPEECH CURVE SYSTEM IEL THRESHOLD Vu 125Hz
37. ve ground 2 Chapter 2 connection by way of the grounding conductor in the power cord is essential for safe operation Grounding The chassis of this product is grounded through the grounding conductor of the power cord To avoid electric shock plug the power cord into a properly wired receptacle before making any connections to the product A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation Do not defeat the safety purpose of the grounding plug The grounding plug has two blades and a third grounding prong The third prong is provided for your safety When the provided plug does not fit your outlet consult an electrician for replacement of the obsolete outlet Danger from Loss of Ground If the protective ground connection is lost all accessible conduc tive parts including knobs and controls that may appear to be insulated can render an electric shock Proper Power Cord Use only the power cord and connector specified for the product and your operating locale Use only a cord that is in good condition Protect the power cord from being walked on or pinched particularly at plugs convenience receptacles and the point where they exit from the apparatus Proper Fuse The user accessible fuse is a part of the IEC AC inlet connector The fuseholder accepts 5 x 20mm diameter fuses For 1 17VAC operation the correct value is 0 25A 250V AC standard For 230V AC
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