Audio-Technica AT-MX351 Musical Instrument User Manual
Contents
1. s designer and or operator Generally speaking use of NOMA is not desirable in applications such as teleconferencing recording or broadcasting Auxiliary Input The Aux input is an RCA jack accepting auxiliary level 10 dBV input from sources such as tape decks and VCRs There is no signal processing of the Aux input Preamplifier Gain The SmartMixer has a substantial gain range allowing it to accept a wide variety of micro phones However if in some instances higher output microphones are used for close talking it may be necessary to reduce the preamplifier gain This can be done by changing switch settings inside the unit With the unit unplugged from its AC source remove the two screws on each side of the unit and carefully lift off the top cover Locate the internal switches designated on the circuit board by SW2 SW8 SW14 and SW20 Figs 4 and 5 page 11 A control map drawing will be found on the inside of the top cover Changing the settings of these internal switches will cause a gain reduction of 10 dB for channels 1 2 3 and 4 respectively The preamplifier gain may be reduced further allowing the SmartMixer to accept line level sources Changing the settings of the internal switches designated by SW3 SW9 SW15 and SW21 will cause an input reduction of 50 dB for channels 1 2 3 and 4 respectively Note that the appropriate internal switches can be used in combin2. Technica brand products purchased in the U S A are warranted for one year from date of purchase by Audio Technica U S Inc A T U S to be free of defects in materials and workmanship In event of such defect product will be repaired promptly without charge or at our option replaced with a new product of equal or superior value if delivered to A T U S or an authorized service center prepaid together with the sales slip or other proof of purchase date Prior approval from A T U S is required for return This warranty excludes defects due to normal wear abuse shipping damage or failure to use product in accordance with instructions This warranty is void in the event of unauthorized repair or modification For return approval and shipping information contact the Service Department Audio Technica U S Inc 1221 Commerce Drive Stow Ohio 44224 Except to the extent precluded by applicable state law A T U S will have no liability for any consequential incidental or special damages any warranty of merchantability or fitness for particular purpose expires when this warranty expires This warranty gives you specific legal rights and you may have other rights which vary from state to state Outside the U S A please contact your local dealer for warranty details audio technica Audio Technica U S Inc 1221 Commerce Drive Stow Ohio 44224 330 686 2600 P51025 B W 1997 Audio Technica U S Inc Printed in U S A
3. o TEEF pa Selected a o 7234 Manual Lockout Figure 1 Front panel AT MX351 Rear Panel 1 External Control connector For TTL output plus closure control input for external control of each channel Link In Link Out Provides for daisy chaining of multiple mixers when more than four microphones are used Line Mic balanced output Level can be changed via internal switch see page 11 XLRM type connector Unbalanced line level 10 dBV output RCA jack Aux In Unbalanced line level 10 dBV auxiliary input Preamp Outputs Independent unbalanced 10 dBV switchable pre post controller outputs from mic channels Inputs Balanced microphone inputs for low impedance dynamic or condenser mics Can be changed to line level inputs via internal switches see page 11 XLRF type connectors Can supply 48V phantom power via internal switches Power input 120V 230V AC 50 60 Hz Select input voltage via switch on bottom panel 4 3 2 1 Figure 2 Rear panel Installation and Setup AT MX351 SmartMixer setup tips 1 Turn the Master level control to the minimum position Proceed with steps 2 9 2 Set all Priority DIP switches and Manual mode switch to down position 3 Turn all four microphone Gain controls fully counterclockwise 4 Connect the power cord to the mixer and plug into AC outlet Be certain the voltage switch on bottom of unit is s
4. product is a safety class 1 product There must be an uninterruptible safety earth ground from the main power source to the product s AC input Whenever it is likely that the protection has been impaired disconnect the power cord until the ground has been restored A Caution To prevent fire or shock hazard do not expose this appliance to rain or moisture A Note Line Voltage Selector Switch You will find the line voltage selector switch on the bottom panel Before your model is shipped from the factory the switch is set to the power requirements of the destination Nevertheless you should check that it is set properly before plugging the power cord into the wall outlet If the voltage requirements differ adjust the selector switch as follows Before adjusting discon nect the power cord 1 Provide yourself with a medium size screwdriver 2 Change the position of switch to the proper voltage for your area A Caution For continued protection against fire hazard replace only with same type rating of fuse A Warning There are some sharp edges inside To reduce the risk of injury do not remove cover Introduction Please Note This manual assumes use of microphone level inputs and line level output the most typical SmartMixer application However all inputs and the output may be individually switched internally to achieve any combination of mic and line level input output See page 10 for details What is a S
5. AT MX351 SmartMixer Automatic Mixer Installation and Operation audio technica Contents Introduction 5 What is a SmartMixer anios 5 Features a a i as a Se e a E A ta st 5 Front Panel inn ara nnibnn aminas 6 AA Mea Saeed Seana Acree hams te enh oh ee hs 7 Installation and Setup 8 Priority Microphones and Lockout BUS occ ett 8 NAAA E POE IT A Oe aI 9 Auxiliary INP Ut ee me ae ea E ie iaa ee e 9 Preamplifier Gain anno 9 OUTPUT level saen een A E E E one E E A 10 Phantom ROW Cea hat a ri aA E 10 Output Level LED Meter oreren E E E tnttntnnttn 10 Adjusting Off Attenuation a ere r iA AE Ar E EaR a TO RAT e 12 Preamp OUDUTS sennoina istava nean RRA AES EENE ENA td 12 A E E O O A 12 Force on Fotce 0ff ose ccscsecine genes genanegenvsugedinesaneragenbnegentsugelinegendsusensnegenisegedinenesenteeseneceseneuadaneaenes 12 Control Voltage QUE torcida natalia 13 Daisy chaining Mixers renace E ENE 14 RACK MOUNT iii ls 14 DO CUMILY CAS id acces 14 Specifications occ 15 Warranty en a ee ee eee ee eee ee ee eee eee ee eer Back cover Safety Cautions Prior to use of this product review all safety markings and instructions CAUTION AVIS RISK OF ELECTRIC SHOCK RISQUE DE CHOC ELECTRIQUE DO NOT OPEN NE PAS OUVRIR To prevent electric shock do not remove the cover There are no user serviceable parts inside Refer all servicing to qualified service personnel A Warning This apparatus must be grounded This
6. Independent adjustable limiters are available on all mic channels To adjust the limiter threshold of channel 1 unplug the unit remove the top cover and locate the trimpot designated on the circuit board by VR2 Figs 4 and 5 page 11 It is factory set at approximately 0 dB RMS When the control is turned fully counter clockwise limiter threshold is approximately 10 dB RMS Conversely when the adjustment is turned fully clockwise limiter threshold is approximately 10 dB RMS VR5 VR8 and VR11 adjust limiter threshold for channels 2 3 and 4 respectively Changing the settings of the switches designated on the circuit board by SW4 SW10 SW16 and SW22 will turn off the threshold limiting function on channels 1 2 3 and 4 respectively Force on Force off To activate force on force off install a closure between the appropriate pin and Ground Reference on the External Control connector on back of unit External Control Connector Pinout Pin 1 Channel 1 force off Pin 8 Channel 4 force on Pin 2 Channel 2 force off Pin 9 Channel 1 TTL out Pin 3 Channel 3 force off Pin 10 Channel 2 TTL out Pin 4 Channel 4 force off Pin 13 Ground reference Pin 5 Channel 1 force on Pin 14 Channel 3 TTL out Pin 6 Channel 2 force on Pin 15 Channel 4 TTL out Pin 7 Channel 3 force on 12 Control Voltage Out When a microphone channel turns on as indicated by a Selected Channel LED on the front panel
7. Priority Pre select switches then determine whether or not a particular mic is affected by lockouts caused by other mics a channel Priority switch in the down position will allow lockout of its mic the same switch up will not allow lockout of its mic Note that any mic which is described as locked out or off is really just being attenuated by between 6 dB and 40 dB from the level otherwise determined by its Gain control setting sensitivity and placement See the Daisy chaining Mixers section on page 14 for further details There are basically three modes of priority pre select automatic operation Mode 1 Priority Pre select switches 1 4 Up The Lockout indicator will come on with any audio input but no mic will be locked out because none are connected to the lockout bus This mode is often called Free for all or sometimes City Council Mode 2 Priority Pre select switches 1 4 Down In this mode only one mic at a time can be on The lockout bus shuts down all other mics until the first speaker pauses As soon as the controlling microphone goes silent the lockout bus goes inactive and any other mic can come on This switching takes place without any syllable grabbing delay or pops or clicks This mode is known as First come first served or Filibuster This mode is very useful when the gain setting of the overall sound system must be close to the threshold of
8. To adjust the off attenuation of channel 1 unplug the unit remove the top cover and locate the trimpot designated on the circuit board by VR3 Figs 4 and 5 page 11 It is factory set at approximately 8 dB the attenuation at the middle of the control s rotation When the control is turned fully counter clockwise off attenuation is approximately 20 dB Conversely when the adjustment is turned fully clockwise off attenuation is approximately 6 dB VR6 VR9 and VR12 control off attenuation for channels 2 3 and 4 respectively Changing the settings of the switches designated on the circuit board by SW5 SW11 SW17 and SW23 will extend the range of off attenuation to 40 dB for channels 1 2 3 and 4 respectively Preamp Outputs Each microphone channel has an independent unbalanced preamp output that is separate from the main mixer output This is helpful when it is necessary to record the output of each channel whether or not it is the active mixer output as is required for example in some courtroom proceedings As set at the factory no gating is applied to these outputs To gate these outputs unplug the unit remove the top cover and locate the switches designated on the circuit board by SW6 SW12 SW18 and SW24 Figs 4 and 5 page 11 Change the switch position s to Gating for channels 1 2 3 and or 4 respectively as desired Input Limiters
9. W13 Sw19 10 dB Input Atten SW2 SW8 SW14 SW20 50 dB Mic Line Atten SW3 sw9g SW15 Sw21 SW26 Limiters on off SW4 SW10 SW16 SW22 Off Atten Range SW5 sw11 SW17 SW23 Preamp Output Gating SW6 SW12 SW18 SW24 Limiter Thresholds VR2 VR5 VR8 VR11 Off Atten Adjustment VR3 VR6 VR9 VR12 NOMA SW25 Meter RMS Peak SW27 Figure 3 Summary of internal controls 10 Rear Panel Front Panel Figure 4 Internal view of mixer Mic Mic Mic Mic SW3 E sw9 E SW15 E sw21 E Line Line Line Line Line Phantom 40 dB Phantom 40 dB Phantom 40 dB Phantom 40 dB Output SW26 Sw1 sw2 SW7 SW8 SW13 SW14 SW19 SW20 Mic Off 30 dB Off 30 dB Off 30 dB Off 30 dB Off Off Off Off SW6 E SW12 E SW18 E SW24 E Gating Gating Gating Gating D 20 dB S 20 dB D 20 dB 6 20 dB Min gt gt 6 dB E SW5 Min lt 6 dB fm Min gt gt 6 dB wn Min lt 6 dB Ela 40 dB 40 dB 40 dB 40 dB p p p S 10 dB lt gt 10 dB 10 dB lt gt 10 dB 10 dB lt gt 10 dB 10 dB lt gt 10 dB On Meter NOMA E sw25 sw27 Peak lt gt RMS Off SW4 SW10 SW16 SW22 or On or on off On of On Figure 5 Detail of internal controls 11 Adjusting Off Attenuation In instances when the number of microphones in use is high it may be necessary to increase the amount of off attenuation per microphone to keep the total ambient noise level low There are off attenuation adjustments inside the unit
10. ation for a total sensitivity reduction of up to 60 dB for each channel Output Level The SmartMixer s output is factory set at line level Should mic level output be desired simply unplug the unit remove the top cover and locate the switch on the circuit board marked SW26 Figs 4 and 5 page 11 Changing the setting of this switch will cause a 50 dB reduction in output Phantom Power Each of the SmartMixer s inputs supplies 48V DC phantom power Should it be required to disable the phantom power simply unplug the unit remove the top cover and locate the switches designated on the circuit board by SW1 SW7 SW13 and SW19 Figs 4 and 5 page 11 Changing the settings of these switches will disable phantom power on channels 1 2 3 and 4 respectively Note that although they do not require phantom power for operation most balanced output dynamic microphones can be used without disabling the SmartMixer s phantom power Output Level LED Meter The Output Level LED meter is factory set to indicate RMS output Should peak output indication be desired simply unplug the unit remove the top cover and change the setting of the switch designated on the circuit board by SW27 Figs 4 and 5 page 11 Zero 0 level is factory calibrated at 4 dBm into 600 ohms Summary of Internal Controls Function Ch1 Ch2 Ch3 Ch4 Output 48V Phantom Power sw1 SW7 S
11. audio technica AUTOMATIC MIXER AT MX351 Output Level AT MX351 Front Panel 1 2 10 11 12 Power switch Power on indicator Input Gain controls Adjust inputs for microphone sensitivities and or operating conditions Selected Channel LED indicators Indicate which channels are on or active Aux In control Adjusts input for source output level and or operating conditions Output Level LED meter Indicates RMS output level of the mixer Zero 0 level is factory calibrated for an output of 4 dBm into 600 ohms Master level control fully clockwise Can be set for peak output level indication via internal switch see page 11 Priority Pre select switches 1 4 A switch in the up position assigns the respective channel priority over the other channels A priority channel can not be locked out by other channels Any combination of priority non priority selections is allowed Manual mode switch Setting this switch in the up position bypasses all of the SmartMixer s automatic functions except limiting and NOMA if selected Lockout LED indicator Shows when lockout bus is active Master level control Adjusts mixer output level for operating conditions Headphone output TRS jack Monitor headphone level control 5 m2 Gain 1 Gain 2 Gain 3 Gain 4 e o o A eee o ERA e 20 10 6 3 0 3 6 CY Y CY CY 3 A Priority Pre select
12. er 14 Specifications Input Impedance Mic Output Impedance Balanced Maximum Output Level Nominal Output Level 0 VU Balanced Line Mic Unbalanced Preamp Out Maximum Monitor Output Maximum Gain Frequency Response Equivalent Input Noise Input Attenuation Mic Line Input Pads Maximum NOMA Attenuation Microphone Phantom Power Control Voltage Out Power Supply Operating Temperature Dimensions Weight Accessories Included 8 000 ohms 50 000 ohms 50 000 ohms 20 000 ohms 24 dBV 27 dBV 17 dBV 22 dBm 4 dBm 600 ohms 4 4 dBV open circuit 46 dBm 600 ohms 44 dBV open circuit 10 dBV open circuit 10 dBV open circuit 700 mW 20 ohm load 73 dB 40 Hz to 22 kHz 128 dBV 150 ohms at maximum gain 10 dB 50 dB 20 dB up to 100 mics on simultaneously 48V DC 4V DC 120V 230V AC switchable 50 60 Hz 10W 32 to 104 F 0 to 40 C 16 93 430 mm W x 9 38 327 mm Dx 1 75 44 mm H including feet knobs and connectors 6 lbs 13 oz 3 1 kg AC power cable AT8325 1 0 Link Cable rack mount adapters security caps t In the interest of standards development A T U S offers full details on its test methods to other industry professionals on request Master Level control at maximum fully clockwise 1 Input terminated with 150 ohms A weighted using Audio Precision System One 15 One Year Limited Warranty Audio
13. et for the voltage of the outlet you are using 5 Turn Power switch on The mixer will perform a self test and turn each microphone on and off consecutively 6 Connect a microphone to Input 1 and turn the Gain 1 control to the nine o clock position The channel 1 LED will light if the microphone is operational 7 Adjust the Gain 1 control for proper meter indication when speaking into microphone peaks at 0 8 Plugin up to three other microphones and adjust each respective Gain control for proper meter indication 9 Priority can be assigned to one or more microphones by moving the appropriate DIP switch es to the up position Any microphone s assigned in this manner cannot be locked out by any other microphone 10 Manual mode can be selected at any time by moving the right hand DIP switch to the up position In this mode the unit will behave like a conventional mixer all automatic functions are bypassed except for limiting and NOMA if selected 11 Adjust the Master level control for desired output level This control is at the last stage in the mixer and does not affect microphone gain threshold setting meter indication monitor or preamp outputs Priority Microphones and the Lockout Bus Channels 1 4 Once the Gain controls have been properly adjusted an audio signal appearing in any channel causes the lockout control bus to activate and the Lockout LED indicator to light The
14. feedback and additional microphones coming on could throw the system into feedback The SmartMixer will not allow multiple microphones to be on at the same time in this mode The switching is so fast and silent that the meeting can still be completely interactive Mode 3 One Priority Pre select switch Up The selected priority microphone can come on at any time and can override any other mic that is on popularly called The Chairperson mode Note that there may be special circumstances where two or three mics could be set to priority so those speakers could talk whenever desired but still override one or two non priority mics If multiple SmartMixers are used with AT8325 1 0 Link Cables Priority Pre select switches on all channels in use will have the control effects described above NOMA The NOMA is factory set in the off position To turn on the NOMA function unplug the unit remove the top cover and change the setting of the switch designated on the circuit board by SW25 Figs 4 and 5 page 11 NOMA serves to maintain overall system gain by proportionately reducing amplifier gain as the number of open microphones increases In a sound reinforcement system this can tend to preserve the feedback margin and system stability However this action necessarily reduces the sound level of each individual person speaking which may not be desired In the end use of NOMA often comes down to the preferences of the system
15. ings results in three different modes of priority selection operation In any of the three modes of operation when everyone stops talking the last microphone on will remain on In a teleconferencing recording or broadcast application this feature will provide continuous room ambience This feature is cascaded throughout all linked mixers so that only one microphone in the entire system will remain on When a microphone is off its input is only attenuated This attenuation is factory set at 8 dB The amount of off attenuation can be internally adjusted between 6 dB and 40 dB if desired See page 12 Adjusting Off Attenuation If automatic switching is not desired a manual DIP switch setting on the front panel bypasses the AT MX351 s automatic switching and attenuation functions causing the unit to behave like a conventional mixer In this mode the relative level of each microphone is strictly a function of the position of its respective front panel gain control NOMA Number of Open Microphones Attenuated The NOMA system helps control feedback by allowing for the increase in system gain that occurs when the number of open microphones increases A built in matrix in the AT MX351 recognizes exactly how many microphones are on and automatically adjusts the gain accord ingly Because use of NOMA is not always appropriate or desired the AT MX351 is shipped with the NOMA function switched off
16. martMixer The AT MX351 SmartMixer is a microprocessor controlled automatic switching five channel mixer The four microphone inputs are XLRF type balanced with 48 volt phantom power available on pins 2 and 3 The Aux input is an RCA jack accepting auxiliary level input from sources such as tape decks and VCRs There is no signal processing of the Aux input The mixer output is XLRM type balanced non inverting All AT MX351 and AT MX341a SmartMixers can be daisy chained via the included AT8325 1 0 Link Cable and special connectors on the rear panel The control bus and the audio are carried between mixers by the link cable The result is that all microphones on a multi mixer system can be controlled by one microphone connected to any mixer Since all of the mixers are independently powered there is no practical limit to the number of SmartMixers that can be daisy chained Features The AT MX351 provides an independent gain control on the front panel for each input channel Substantial gain reserve and adjustment range permit microphones of widely differing sensi tivities to be used together successfully Automatic threshold setting on all mic line channels ensures proper gating levels for existing ambient sound conditions Priority Pre select To custom tailor conferencing needs the mode of each microphone channel can be indepen dently switched via the front panel Priority Pre select DIP switches The combination of switch sett
17. peaking Note that one or more mixers can be switched to Manual mode without affecting the automatic operation of any other mixers in the chain NOMA information is passed between AT MX351 mixers through Link In Out If AT MX351 mixers are linked with AT MX341 and or AT MX341a mixers the NOMA function will pass through the AT MX341 a models but their mics will not be included in the NOMA calculation Rack Mounting Provided with each mixer are two rack ears and six self tapping screws to attach the ears to the unit which allow the unit to be mounted in a 1U rack space Security Caps For permanent installations where microphone selections positions and acoustic conditions are constant it may be advantageous to remove the front panel knobs and install security caps to prevent unauthorized adjustments To install simply press the caps into place covering the desired control s The system should be tested carefully before installing the security caps because they are intended to be permanent and are very difficult to remove If removal of installed security caps becomes necessary unplug the mixer remove the two screws on each side of the unit and remove the top cover Then remove the nine screws that attach the front panel six on top and three underneath Remove the front panel With the panel removed the two locking tabs on each security cap can be accessed The cap can be released by carefully squeezing the two tabs togeth
18. the channel s associated Control Voltage Out goes high 4 VDC See chart on page 12 for pin connection This signal can be used to light indicator lamps switch speaker zones on and off select video cameras etc The control voltage should not be connected directly to an inductive load such as a relay coil as damage to the mixer may result Several interface circuit possibilities are shown in Figure 5 below Equivalent Output Driving One LED Circuit for Control oy Voltage Out I R4400 CV CONTROL Pa VOLTAGE R Za JIL GND G pa Relay Driver Driving Lamps IN4001 CV 2N3904 2N3904 Driving Logic Gates Figure 5 Control interface examples 13 Daisy chaining Mixers When more than four microphones are needed it is possible to daisy chain multiple SmartMixers together through the Link In Out connectors on their back panels Fig 2 Connect Mixer 1 Link Out jack to Mixer 2 Link In jack etc Mixer 1 output contains only audio from the first four microphones Mixer 2 output then contains audio from all the microphones plugged into Mixer 1 and the microphones plugged into Mixer 2 The last mixer in the chain contains audio from all preceding mixers The combined output is then taken from the last mixer in the chain Because lockout information is passed between mixers through Link In Out the last microphone on condition is not violated Thus only one microphone per installation will stay on when no one is s
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