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Page 42

MICROPHONE PREAMPLIFIER

Page 43

Instruction Manual

APPENDIX D

PART 2: BALANCED OUT to UNBALANCED IN

It was mentioned that there are several types of
balanced output stages in use today. The follow-
ing diagrams show you how to properly unbal-
ance each type of output. If you follow these
instructions, you should have no problems.

SIMPLIFIED SCHEMATIC

Transformer Balanced Outputs

Mono Phone Plug

Female XLR

Servo Balanced Outputs

Mono Phone Plug

Female XLR

SIMPLIFIED SCHEMATIC

Voltage Balanced Outputs

Mono Phone Plug

Female XLR

SIMPLIFIED SCHEMATIC

Don’t Ground or Connect Pin 3

Ground Pin 3 Directly to Pin 1.
Alternatively, Carry Pin 3 Through Twisted Pair Cable
and Ground at Other End

Ground Pin 3 Directly to Pin 1

Do Not Carry Pin 3 Through Cable and Ground

at Other End

Impedance Balanced Outputs

Female XLR

SIMPLIFIED SCHEMATIC

Pin 3 Doesn’t Matter
OK Grounded or Not Grounded

Unbalancing loses half the output level.
You lose 6dB of gain.

Unbalancing loses no output level.
You retain full gain.

Mono Phone Plug

Содержание 1788A

Страница 1: ...e of the 1788A R dedicated hardware remote control unit Please be sure to maintain a copy of that manual together with this one P N 999 4320 Revision 1 Released 05 12 2005 Manufactured by Aphex System...

Страница 2: ...n the digital domain and also assures maximum resolution All these patented features make the 1788A an indispensable tool for live or studio applications We are extremely pleased that you have joined...

Страница 3: ...T BLOCK 21 4 6 SECONDARY FUNCTIONS 22 4 6 1 Display Brightness 22 4 6 2 Flash Version 22 4 6 3 Synchronize 22 4 6 4 Sysex Dump 22 5 USING THE DIGITAL MODULE 23 5 1 SYNCHRONIZATION 23 5 2 SENDING DIGIT...

Страница 4: ...s in front of the preamplifier to prevent overloading the front end Now you don t have to worry about clipping and you can run higher gain and higher average output level This translates not only to d...

Страница 5: ...NA we give you gain stops stable gain set points in 1dB increments that are ramped through inaudibly minute 1 4dB steps smooth as a baby s bottom Presets Another Advantage The ability to create and sa...

Страница 6: ...es a 12dB octave low cut filter with a corner frequency of 75hz 12 ADJUST STORE arms the ADJUST control so that MIDI Channel and Device numbers and Net numbers can be adjusted After adjustment the STO...

Страница 7: ...OR for standard CAT5 Ethernet connection 4 RS 232 COM Port for downloading new firmware into the preamp 5 DIP SWITCH sets priority for external synchronization 6 AES EBU DB 15 DIGITAL OUTPUT provides...

Страница 8: ...cts CAUTION 2 It has been reported that some ribbon mics may be damaged by phantom power This is unusual but it s a good idea to keep it turned off when not required 4 At this point you can try all th...

Страница 9: ...ween 12dB and 6dB of headroom 8 If the input gain is set at its lowest setting 26dB and the level is still too hot use the 26dB PAD 9 To test the MicLim protection select ENABLE LIMITER You will easil...

Страница 10: ...oducing equipment and whether the air is moving or still It is always best to err on the safe side We recommend at least one free rack space be allowed between each 1788A The space between units may b...

Страница 11: ...female 3 pin XLR s wired with pin 2 positive 3 6 OUTPUT CONNECTORS Two separate analog outputs per channel are provided 1 Transformerless servo balanced Main Outputs on eight separate XLR s 2 Eight tr...

Страница 12: ...mper option The LOADED mode is shipped by default and the user will have to change the jumper to try the UNLOADED mode CHANGING THE MODE Remove the 1788A s top cover and locate the set of jumper pins...

Страница 13: ...le from your computer s Com Port to the 1788A s Com Port 3 Power up the 1788A while holding down both Test Tone buttons Load A will appear in the Global Readout Display 4 Run the update program on you...

Страница 14: ...ntrols are in front of the variable gain amplifier and will therefore affect the Aux Output in both PRE and POST modes In the above example if the pad is suddenly engaged by the FOH operator then a dr...

Страница 15: ...ash double dash marks to indicate their muted status The flashing dash marks will alternate with the current gain setting Even though both analog outputs are muted the digital outputs will not be mute...

Страница 16: ...ill be accurate up to 21dB as that is the maximum output level when running Main Output unbalanced Higher gain settings than 21dBu will be inaccurate but will not cause any distortion If you are using...

Страница 17: ...12dB per octave low cut filter is provided In general this filter could be engaged when mic ing vocals as it will not usually affect the tonality of the human voice When mic ing instruments with very...

Страница 18: ...n the Local Block is pressed Then all grouped channels will take up that particular function state All uncommanded functions of the grouped channels will remain in their prior individual state 4 2 CON...

Страница 19: ...s for the 1788A MIDI or LAN No matter whether you are using the MIDI or the LAN port for remote control you must first put the Mode into MIDI in order to be able to change the Set I D parameters Once...

Страница 20: ...e settings on the Model 1788A will be stored upon entering the remote control state This insures that the locally made changes will not revert to the prior state and will become the new default condit...

Страница 21: ...e it for other test tones When the test tone is activated for any given channel or group of channels several things happen First a low level tone is substituted for the mic input jack Second the pream...

Страница 22: ...RY FUNCTIONS 4 6 1 Display Brightness You can dim or brighten the front panel display by holding down BOTH TONE BUTTONS and pressing the Channel 7 button This puts the 1788A into display mode Turning...

Страница 23: ...ke three types of external sync All are received at the BNC Word Clock IN jack 1 Word Clock 2 Superclock 256 times sampling frequency 3 AES EBU Signal Dip Switch Settings Sync is detected according to...

Страница 24: ...ut jack to properly terminate the transmission line If only one unit is connected then simply place the terminator plug on the single unit s Clock Out jack When the Model 1788A is operating in the int...

Страница 25: ...8 MIC IN LINE OUT CH 7 MIC IN LINE OUT CH 6 MIC IN LINE OUT CH 5 MIC IN LINE OUT CH 4 MIC IN LINE OUT CH 3 MIC IN LINE OUT CH 2 MIC IN LINE OUT CH 1 MIC IN LINE OUT AES EBU OUTPUT LAN TDIF ADAT IN OU...

Страница 26: ...MIC IN LINE OUT CH 4 MIC IN LINE OUT CH 3 MIC IN LINE OUT CH 2 MIC IN LINE OUT CH 1 MIC IN LINE OUT AES EBU OUTPUT LAN TDIF ADAT IN OUT UTIL 1 2 3 4 ON P MODEL 1788A 8 Channel Mic Pre Aphex Systems S...

Страница 27: ...haracteristic impedance then there will be no overshoot or ringing of the word clock even at great distances The only complication is that the pulse amplitude received will be half the amplitude of th...

Страница 28: ...so you can make suitable breakout adapters TDIF Jack The pinout is standardized by Tascam We have reproduced their wiring diagram for you for reference only We highly recommend that you obtain commerc...

Страница 29: ...that the line input does indeed bypass the microphone preamp stage Many consoles route the line input through a loss pad right into the mic preamp In such a case you will still hear the deficiencies...

Страница 30: ...en the signal fed to the individual recorder tracks is kept pure and natural Effects and processing are added later during the mix down process In this situation you can bypass the mixing console alto...

Страница 31: ...h a thousand words The above illustration gives you an idea of the flexibility of the 1788A Substitute a digital house or monitor mixer analog recorder or any other combination as your design may requ...

Страница 32: ...lly 20dB of limiting headroom Effectively that means you get 20dB more preamp headroom before distortion 6 5 USING POLARITY REVERSE There will be times when you need to reverse the polarity phase of a...

Страница 33: ...their new ratios or differences 2 The individual channel functions will remain unchanged within the group until a function is operated At that time whatever function is operated passes to all in the g...

Страница 34: ...ct unauthorized product modification or failure to follow instructions contained in the User s Manual 3 Resulting from repair or attempted repair by anyone not authorized by Aphex Systems 4 Occurring...

Страница 35: ...DIGITAL AUDIO Internal Sample Rates External Sample Rates Resolution Word Clock Input Word Clock Output Dynamic Range Noise Dither Level Equivalency 32KHz 44 1KHz 48KHz Automatically syncs to any word...

Страница 36: ...e Main outputs shall occupy individual XLR 3 pin male connectors All eight Aux outputs shall occur on a single 25 pin D Sub connector conforming to the Tascam analog standard pinout The digital output...

Страница 37: ...t levels This tutorial will teach you about the principles of balanced and unbalanced lines wiring standards and how to effectively interface them Standards Professional audio equipment usually comes...

Страница 38: ...unds and there can be a sig nificant difference of ac voltage between alternating wall outlet grounds For this reason unbalanced sys tems can sometimes never be made hum free and just changing one pie...

Страница 39: ...resistance ground current paths that little current is left to flow through your audio grounds You can try adding heavy gauge for example 12 gauge copper wire from chassis to chassis You will need to...

Страница 40: ...e standard balanced line wiring recommenda tion from Aphex Engineering is this In the majority of cases maximum noise rejection occurs when the shield is connected to the input ground only espe cially...

Страница 41: ...Ground Shield Earth Screen Pin 2 Tip Positive Signal High Hot Pin 3 Ring Negative Signal Reference Return Low Common 1 4 TS Phone RCA Standard Wiring Convention Unbalanced Tip Center Pin Positive Sig...

Страница 42: ...andard store bought cable Shield is grounded at both ends Positives Both ends are interchangeable Negatives May cause ground loops through shield contacts BETTER Custom cable Shield is grounded at rec...

Страница 43: ...Voltage Balanced Outputs Mono Phone Plug Female XLR SIMPLIFIED SCHEMATIC Don t Ground or Connect Pin 3 Ground Pin 3 Directly to Pin 1 Alternatively Carry Pin 3 Through Twisted Pair Cable and Ground at...

Страница 44: ...ALANCED IN Mono TS Phone Plug Stereo TRS Phone Plug Standard Method Standard Cable Guitar Cord Mono TS Phone Plug Stereo TRS Phone Plug Enhanced Method Pseudo Balanced Advantage Reduced Hum and Noise...

Страница 45: ...nbalanced Unbalanced Unity Gain2 Balanced Balanced Unity Gain2 Wire single conductor with a shield coax style Wire two conductor with a shield twisted pair Wire two conductor with a shield twisted pai...

Страница 46: ...unded to the equipment s ground though the XLR ground drop s case XLR ground drops are useful especially for live sound situations where the same stock of XLR cable may be used for line level patching...

Страница 47: ...All matched transmission lines have losses especially at high frequencies When the cable exceeds a certain length depending on the cable s quality cable equalization may be required to recover additi...

Страница 48: ...gnitude of jitter rapidly rises Very short cable runs are necessary Every piece of gear gets a separately driven feed and no terminating load is used Figure 4 above illustrates the Brute Force clock p...

Страница 49: ...ine the best option for terminating the line as shown in figure 5 Clocking The 1788A With Brute Force Not knowing what the 1788A s word clock input may be driven by we made it automatically accept the...

Страница 50: ...under one or more of the following Aphex patents 4 578 648 4 633 501 4 843 626 4 939 471 5 115 471 5 155 769 5 334 947 5 359 665 5 422 602 5 424 488 5 450 034 5 463 695 5 483 600 5 485 077 5 612 612 5...

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