NAGRA 4.2
Contents
1. The Power supply voltage batteries or external becomes insufficient for correct operation of the machine The motor current reaches its maximum limit in this case voltage and speed stabilizer circuit A22 requires the motor to run faster but this is not possible because the automatic current limiter circuit has been activated If this occurs during normal operation then contact your nearest Nagra agent WOW and FLUTTER is out of tolerance Contact Nagra agent Thus when a white segment is indicated the operator can be absolutely sure that the power supply is sufficient that the motor current is correct and that the tape speed is within tolerance 17 HEADPHONES OUTPUT This 1 4 jack type socket type 297 is the headphones output socket accepting headphones with an imped ance of anything from 50 Q to 600 Q 18 HEADPHONES VOLUME CONTROL This small potentiometer is adjustable using a screwdriver and adjusts the level fed to headphones output connector 17 Position 1 is the minimum and position 6 is the maximum 19 REEL FIXING NUT TAPE DECK 20 SPEED AND EQUALIZATION SELECTOR This is a six position rotary switch permitting the selection of the speed and equalization of the 4 2 in both record and playback Possible settings are 3 3 4 ips 9 525 cm s 7 1 2 ips 19 05 cm s 15 ips 38 10 cm s For each of these speed selections there are two possible positions labelled and Il these correspond to diffe2. a precision of the order of 0 001 as any slipping or stretching of the tape is automatically compensated for This applies to average frequencies for inevitably mechanical tolerances and longitudinal vibrations of the tape will affect the instantaneous speed wow and flutter Experience has shown that this precision is more than sufficient for the recording and reproduction of facsimile signals Other telemetering applications are of course possible Pilot Playback Using a Nagra 4 2 L not Equipped with QSLI Synchronizer Output impedance 47kQ 20 Load impedance from zero to infinity Output voltage from tape recorded on Nagra 4 2 L 330 mV 3 dB Pilot Playback Made by Nagra 4 2 L Fitted with QSLI Synchronizer Output impedance 10 kQ 20 Load impedance from zero to infinity Output voltage from tape recorded on Nagra 4 2 L 0 85 V nominal 3 dB The Nagra 4 2 fitted with a QSLI can be used to measure the playback pilot signal 0 85 V corresponds to a meter deflection of 1 V on the scale calibrated from 0 to 2 V and normally used to measure the voltage per cell of the batteries 1 7 V corresponds to full scale deflection Pilot Connectors On the Nagra 4 2 the pilot playback signal is to be found on Power Pack connector 48 which is a 6 pin Tuchel socket located on the right side of the recorder Pin No 2 is connected to the chassis and the output pilot signal is connected to pin No 3
3. are in service unless of course this takes place from the headphones The Line and Phones snap switch allows meter readings of the playback signal while recording It always snaps back into the DIRECT position Audio Inputs The Nagra 4 2 has 4 inputs 2 microphone inputs 1 asymmetrical line input transformable into a 3rd microphone input by means of an exter nal preamplifier 1 mixer input at fixed level Manual Level Control When using manual level control adjust the position of the microphone potentiometers in such a way that the loudest sounds to be recorded do not exceed the maximum level The potentiometers corresponding to the unused inputs should be kept in their anti clockwise position The active potentiometers can be equally used to give a compression by increasing the sensitivity during the soft passages and vice verse Limiter The Nagra 4 2 is equipped with a safety limiter which instantaneously reduces the gain of the recording ampli fier when the signal exceeds the maximum level providing that the RECORD with limiter position of the Main Function Selector has been selected This limiting evidently causes distortion but it is less objectionable than that caused by saturation of the tape Normally the limiter will only be brought into action when accidents occur It is possible that in the middle of a dialogue for example a short but high power sound exceeding the maxi mum level can occur Under these
4. connected to the DIRECT signal During recording it measures this level If the line amplifier is connected to the DIRECT Signal LINE AND PHONES switch in DIRECT the measurement will be that of the signal sent along the line On the other hand if the LINE AND PHONES switch is in TAPE the level sent along the line will be independent of the DIRECT signal and will consequently not be measured In any case the level of this signal cannot be altered A signal recorded at nominal level will give a line signal of nominal level CHAPTER 2 PILOT 2 1 INTRODUCTION The Nagra 4 2 NQ L version is equipped with a Neopilot system This system developed by KSA records a syn chronization signal simultaneously with the audio of 50 Hz 60 Hz in NTSC countries Two signals are record ed in phase opposition so as to avoid any interference with the audio replay chain The pilot signal serves as a speed reference to ensure that when the tape is replayed it is always replayed at the same speed at which it was recorded The pilot signal can either be supplied from an external source a film camera for example or can be generated by an optional internal crystal generator QGX 3 If a recording is made with a pilot version of the Nagra 4 2 it is later possible during playback to lock the speed of the Nagra by means of the pilot synchronizer QSLI to an external reference signal This means that provid ing the start point of the recording is kno
5. microphone being used The possi ble selections are T power 12 V and 48 V phantom powering or 200 Q dynamic The level of the signal coming from the microphones may be observed by putting the machine into the TEST position and switching modulmeter switch 12 to the LEVEL position The gain may now be adjusted using potentiometers 6 and 7 on the front panel Turn the main function selector to either of the two RECORD positions depending upon whether the limiter is required or not Observe the modulometer to see that the levels remain correct throughout the recording The modulometer indicates in both RECORD modes the DIRECT signal It is possible to show the OFF TAPE sig nal during the recording by moving the LINE AND PHONES snap switch to the left Depending on the position of TAPE DIRECT switch 1 it is possible to monitor either the input signal or the OFF TAPE signal on the headphones output during the recording This is possible because the Nagra 4 2 has separate heads for recording and playback moving this switch will not affect the recording Recording a Line Signal Recording a line input signal rather than a microphone signal is very similar to working with microphones Set microphone potentiometers 6 and 7 to their fully anti clockwise position this is to prevent any noise to be amplified by the high gain microphone preamplifiers and recorded on the tape Connect the line input signal to line in
6. pass this limit If the needle is deflected less the recording will be of a lower level The sensitivity i e the level of recording for a given sound can be controlled either manually or automatically The choice is made by means of the AUTOMATIC MANUAL switch on the upper left of the front panel In the position MANUAL the level can be controlled by means of potentiometers 6 and 7 In the position AUTO MATIC the level is controlled by an Automatic Level Controller The modulometer deflects with respect to the incoming signal without reaching the extreme right end of the scale Tape Speed and Standard Selection The Nagra 4 2 is capable of running at three different speeds which can be selected by means of SPEED AND EQUALIZATION selector 20 on the top deck of the recorder between the two spools The speeds available are 3 3 4 ips 9 525 cm s 7 1 2 ips 19 05 cm s 15 ips 38 10 cm s Each position of this selector automatically selects the correct equalization of the machine according to the chosen speed There are two different positions available for each speed and they are marked I and II which represent Standard and Low noise respectively For adjustments of equalization and checking of tape speed refer to the 4 2 service manual NOTE The Nagra 4 2 is only equipped with one recording bias oscillator and it is therefore only possible to bias the recorder for one specific tape type at any one time However it is p
7. to be transferred without slaving When using the QSLI internal synchronizer put the Nagra into PLAYBACK without loudspeaker 2 Adjust the speed with the aid of the speed varier QSV 2 in such a manner that the playback pilot signal and the mains are approximately synchronized The needle of the Nagra meter switch on SYNC will not swing 3 Rewind the tape and make the transfer in the usual manner Under these conditions the speed cor rection achieved by the synchronizer will be very small Method B Make the transfer in the classic manner and adjust the speed varier so that the needle in the posi tion SYNC remains at the centre of the scale QSLI This method is less precise but it is sufficient in practice It should be noted however that the interruptions of the pilot signal happen at the begin ning of a sequence and it is almost always necessary to make a trial playback adjust the speed rewind and then make the transfer Use of Speed Varier While Filming on Playback While filming on playback it is possible that the camera may run at an incorrect speed It will therefore be nec essary to adjust the camera if possible to avoid any change in the tone of the final sound If this is not possi ble correction can be made with the speed varier see above Recording of Facsimile and Similar Signals A Nagra equipped with a Quartz Crystal Pilot Generator and a QSLI Synchronizer can reproduce on playback frequencies with
8. 0 V This explains why with new batteries the needle of the meter will only indicate about 40 full scale when it is switched to BATT RESERVE Volt Cell The meter switch in this position works as a simple voltmeter The centre scale is graduated from 0 to 1 6 V it indicates 1 12 of the total voltage or the average voltage of 1 cell The position Volt Cell is essentially designed to monitor the voltage of some accumulators which would be dam aged it they were allowed to discharge below a certain value This value is 1 V Cell for certain manganese diox ide alkaline accumulators It is also possible to monitor the external power supply voltage When in the BATT RESERVE position if the indication is that the Nagra is not receiving sufficient voltage but the Volt Cell indicates that the power supply voltage is correct this means that the Nagra requires an abnormally high voltage Under these conditions the Motor and motor collector should be examined Measuring the Motor Current The meter will measure the motor Current when the meter switch is in the position MOT There is no corre sponding scale on the meter but the VOLT CELL scale can be used Full scale deflection corresponds to a motor current of approximately 250 mA In NO LOAD running i e with out tape and with the pinchwheel separated from the capstan but not in the rewind mode the needle should indicate between 0 2 and 0 3 V If this value is exceeded see chapt
9. E HEAD STROBOSCOPE ROLLER RECORDING HEAD PILOT HEAD PLAYBACK HEAD CAPSTAN SHAFT PINCHWHEEL AND TAPE GUIDE CON TROL LEVER TAPE TENSION ROLLER OR TIMER TAKE UP REEL 1 2 CONTROLS DESCRIPTION AND USE FRONT PANEL 1 TAPE DIRECT SWITCH line and phones When in TAPE position the signal is reproduced directly from the tape When in DIRECT position there are two possibilities a When recording the signal is available before arriving on the tape b When playing back the signal may be adjusted by means of the level control and corrected by fil ter switch 13 NOTE When the machine is in TEST position the output is the direct signal regardless of this switch s posi tion 2 TAPE DIRECT snap switch This switch affects the meter in the same way that the previous switch affects the output Thus when it is held to the left the meter will display the OFF TAPE signal otherwise it displays the DIRECT EE signal 3 POWER SELECTION SWITCH extemal batteries The Nagra 4 2 may be powered by either internal batteries or by an external source which may be selected using this switch See also the Power Supply section of this manual 4 MAIN FUNCTION SELECTOR six position rotary STOP Stops the machine completely from any function and will slightly move the pinch wheel away from the capstan to prevent a flat being caused on the pinch roller In this mode no circuits are powered TEST Will power
10. G AND PLAYBACK EQUALIZATION 1 4 POWER SUPPLY All models of the Nagra 4 2 may be powered either by an external power supply ATN 3 or alternatively by inter nal batteries The 4 2 will accept voltages ranging from 11 V to 30 V with peaks of up to 35 V The batter ies are placed in the bottom of the machine and the polarity is marked inside the battery compartment It is opened by turning the two fasteners with a screwdriver or a small coin All the batteries MUST be orientated in the same direction as indicated on the base of the battery compartment The Nagra 4 2 houses twelve D type 1 5 V cells having a maximum diameter of 33 5 mm and a length of between 59 5 and 62 5 mm It is important to remember that corrosive material can leak out of flat batteries causing severe damage to the recorder and therefore it is recommended not to leave batteries in the machine during periods of storage If leakage occurs as a result of leaving flat batteries in the machine then wash the affected area with fresh water The machine will suffer much less from the water than the electrolyte from the batteries The external supply is fed into the machine via connector marked POWER PACK 48 on the right side of the machine Rechargeable batteries may also be used and can be charged using the ATN 3C order no 14376 which includes the charger circuitry The 4 2 will function when the power is as low as 12 V at 15 ips 38 cm s and down to as low as 10 5 V
11. NAGRA 4 2 PORTABLE ANALOGUE AUDIO TAPE RECORDER INSTRUCTION MANUAL KSA code No 20 04 004 151 Kudelski S A NAGRA Tape Recorder Manufacturer CH 1033 Cheseaux SWITZERLAND phone 021 731 21 21 telex 459 302 nagr ch telefax 021 731 2155 Copyright reserved for all countries February 1991 Edition Orginally printed in Switzerland this is an exclusive digital reprint and may only be used by Hunter College Students 1 1 INTRODUCTION The Nagra 4 2 was introduced originally in 1971 It is a portable 6 35 mm 1 4 mono analogue audio tape recorder designed for high quality recording having radio cinema and television applications Many mechanical and electronic modifications have been made to the machine since its release to adapt it according to modern day requirements Despite all these modifications the machine remains remarkably simi lar to the original The Nagra 4 2 can be delivered in two different versions both of which are available in either NAB or CCIR equal ization These versions are NQ LSP Non pilot NQS L Pilot Each version has three speeds 38 cm s 19 cm s and 9 5 cm s 15 7 1 2 and 3 3 4 ips and has either the NAB or the CCIR standard The Nagra 4 2 is a mono recorder recording full track audio on 6 35 mm tape and the Neopilot synchronization system The audio inputs may be used with either the two internal microphone preamplifiers switchable between Dynamic T power and Phantom pow
12. This is a six position rotary switch allowing different filter possibilities to be switched in or out LFA 2 Low frequency attenuation 8 dB at 50 Hz LFA 1 Low frequency attenuation 4 dB at 50 Hz FLAT The machine has a linear response HP 1 High pass filter 10 dB at 50 Hz HP1 LFA1 Combination of high pass and low frequency attenuation 14 dB at 50 Hz and 3 dB at 400 Hz HP2 High pass filter 20 dB at 50 Hz 14 MODULOMETER This meter is the visual indication of many functions and levels of the machine The modulometer displays infor mation according to the position of mode selector switch 12 The modulometer has 4 scales 1 Recording level in dB 2 Frequency deviation in 3 Battery voltage volts cell 4 Compression 15 PILOT INDICATOR If the machine is fitted with the pilot system this rotary SASS type indicator shows a white segment when the pilot signal frequency is correct NOTE This only indicates the presence of a correct signal being fed to or coming from the head and does not guarantee correct recording of the signal This should be checked by switching the modulometer to PILOT playback this does not function in the RECORD mode 16 SPEED AND POWER INDICATOR This rotary SASS type indicator gives a quick visual indication that the machine is functioning correctly and will indicate a white segment when this is the case It will turn black whenever any of the following conditions occur
13. a white segment the pilot signal will be recorded automatically No further manipula tion of the pilot system is needed Recording an Extemal Pilot Signal Remove the crystal shorting plug in connector 44 and feed pilot input socket 44 by means of the QCP cable The other end of the cable must be connected to the source either an ATN 3 camera Check that the exter nal pilot signal is present by switching the machine to the TEST position as above While making a recording the cable must always be left connected Make the recording as above Synchronizing a Recorded Tape Check that the machine is fitted with the QSLI synchronizer circuit This circuit is located on the right side of the battery compartment inside the machine The circuit faces downwards and has its front right corner cut away Feed pilot input connector 44 with the reference signal either from the pilot out socket on the ATN 3 for syn chronization to mains or from the machine to which the 4 2 is to be synchronized Turn the main function selec tor to the PLAYBACK WITH LOUDSPEAKER position and after a short period typically 1 1 2 secs pilot indi cator 15 should once again show a white segment Check the level of the pilot signal from the tape by switch ing modulometer switch 12 to the position PILOT PLAYBACK The needle should deflect about half way If the modulometer selector is switched to the position SYNCH the meter will indicate the deviation
14. ailable in all positions of the main function selector Current drawn should not exceed 2 A as this may blow the internal fuse if working with internal batteries Playback amplifier output minimum load impedance 100 kQ out put voltage 560 mV at 0 dB Motor stop control terminal connect to 10 V to stop motor Operational in all modes except REWIND It is not recommended to use this remote method in REC as this will magnetize the recording head and reduce performance Ground chassis Banana jack line input connector Input impedance 100 kQ input voltage to obtain 0 dB on maximum sensi tivity 370 mV Maximum voltage up to 150 V This is the value supported by the input resistance but it is not recommended to exceed 10 V as crosstalk might be produced Up to 150 V has been foreseen to allow for connection to a sound distribution system at 100 V nominal 42 VOL Loudspeaker volume control 43 MICROPHONE INPUT SELECTOR This is a four position microphone input selector DYN 200 48 12 Dynamic microphone impedance 200 Q 0 2 mV ubar 2mV pa sensitivity Condenser microphone 1 5 mV ubar I5mV pa sensitivity 48 V phantom powering Condenser microphone 1 5 mV ubar 15mV pa sensitivity 12 V phantom powering Condenser microphone 1 5 mV ubar 15mV pa sensitivity 12 VT powering 49 51 50 47 48 45 46 44 50 44 PILOT AND CLAPPER INPUTS 1 Ground 2 CLAPPER Clapper oscillat
15. all circuits and allow level adjustment by means of level controls 6 7 and 9 In this mode the motor is not powered All indications of the modulometer will be of the DIRECT input irrespective of the position of tape direct switch 1 RECORD Is the first of the two RECORD positions and corresponds to RECORD WITH LIMITER where the recording level is limited to 4 dB This level remains constant when the input level is between 4 dB and 10 dB Thus in this position tape saturation cannot occur and distor tion is avoided RECORD The limiter is inactivated in this position so that recordings that should be saturated can be no limiter made e g gun shots or explosions PLAYBACK Is the first of the two playback possibilities and corresponds to playback of the tape to the head phones and line output only PLAYBACK This position is exactly as above only it allows monitoring via the internal loudspeaker at the same with time This is also the only position of the main function selector that permits the FAST FOR speaker WARD function to be performed 5 PINCHWHEEL LIFTER stop test only 6 LEVEL CONTROL mic Input 2 7 LEVEL CONTROL mic Input 1 These are the main level controls for the two microphone inputs 8 REFERENCE OSCILLATOR push button On the lower edge of the front panel between the line and playback potentiometer and the mic 2 potentiome ter is the reference generator push button When this but
16. andling and positioning During nor mal use neither of these two rollers should be at either end of its travel If this is the case refer to the Mechanical Calibration section of the service manual The two rollers can be replaced by either the QTIM or QLEN tape measuring rollers The QTIM is supplied in the place of the take up reel tension roller as standard equipment QLEN instead of QTIM is optional To be stated when ordering 26 ERASE HEAD This is a full track erase head 27 STROBOSCOPE ROLLER This roller comes in two versions 50 Hz CCIR machines and 60 Hz NAB machines Using this roller it is possible to check that the machine is running at the correct speed either in record or playback This works at all speeds and uses the stroboscopic effect whenever a mains powered lamp is shone upon it When at the cor rect speed the bars on the roller should appear stationary 28 RECORDING HEAD Audio recording head 29 PILOT HEAD Neopilot head used for both recording and playback of pilot signals 30 PLAYBACK HEAD Audio playback head 31 CAPSTAN SHAFT Tape main drive 32 PINCHWHEEL AND TAPE GUIDE CONTROL LEVER This lever engages and disengages the tape from the heads and motor capstan shaft It also moves the stroboscope roller and mobile tape guide in and out to allow easy loading of the tape When it is in the open position rapid rewinding is possible This lever should never be left in the open po
17. at the lower speeds These figures correspond to a machine in perfect condition and working at room temperature When using an external supply selector switch 3 must be in the EXTERNAL position It must be in the BAT TERIES position when internal batteries are in use It is not necessary to remove the batteries when working with an external supply and vice versa Danger of Reversed Polarization A reversed polarization of the power supply negative to ground could cause serious damage to the unprotected early versions of the Nagra 4 2 Since then three 2 5 A fuses have been added in the battery compartment which protect the Nagra when batteries or accumulators are used A fourth fuse mounted in parallel in the wiring fur ther protects the machine when powered by batteries as well as when powered by an external supply Measuring Battery Condition and Power Supply Voltage Battery Reserve When the Meter Switch is put into the BATT RESERVE position the meter will indicate the difference between the power voltage available and the power which the Nagra needs Often the two voltages will fluctuate The device will take into consideration the lowest instantaneous voltage and memorize this This detail is important for the average voltage of a power supply can be sufficient but momentary drops in the voltage can happen and drop lower than the required minimum New batteries will give about 18 V whereas the Nagra can be powered by up to 3
18. between the external pilot reference and the pilot signal from the tape Frequency Meter optional accessory QFM This device measures the frequency of the pilot signal If the meter switch is in the PILOT FREQUENCY posi tion the meter will indicate the frequency The scale is from 4 on the left side to 4 on the right The accu racy is about 0 1 on the centre of the scale In addition the frequency meter circuit gives a warning if the frequency is more than 5 out from its nominal value It this is the case the rotary Pilot indicator turns black The QFM exists in two versions for 50 Hz and 60 Hz QFM 50 and QFM 60 Quartz Crystal Pilot Generator optional accessory QGX 3 This accessory is designed for synchronous filming without cable between the camera and the Nagra It supplies a signal whose frequency is 50 Hz 0 001 and is very stable within a wide temperature range A dummy plug is supplied with the generator The solution of using a dummy piug rather than a switch has been adopted in order to reduce the risk of human error The QGX 3 is switchable and gives a 50 Hz or 60 Hz signal Pilot Indicator This device is found on the upper right of the front panel It shows a white cross when the Nagra is in operation and it a pilot signal of sufficient amplitude is provided and if there is no Alarm signal in the pilot system The Alarm signal will appear and turn the indicator black if the following conditions occur a
19. conditions it is preferable to saturate rather than to limit because the satu ration will be practically unnoticeable due to the short duration of the sound Moreover the limiter requires a certain recovery time before the normal sensitivity of the chain is re established This sensitivity variation can allect the ambient sound and can be a greater nuisance than saturation by a brief sound To avoid this phe nomenon it is necessary to reduce the recovery time of the limiter Detailed instructions as to how this can be done will be sent on request The limiter can be switched off by setting the Main Function selector to position RECORD NO LIMITER This may be advantageous for certain recordings e g gunshots explosions where tape saturation is desired Automatic Level Control ALC The Nagra 4 2 is fitted with an Automatic Level Control It replaces the manual potentiometer when the selector switch placed on the left of the meter is on the position AUTOMATIC In the position 1 AUTOMATIC only microphone No 1 has its sensitivity controlled automatically Microphone No 2 is controlled by its respective poten tiometer In 2 AUTOMATIC both microphone inputs are controlled by the ALC circuit The operation of the ALC is complex It is useful to place the meter switch in the position COMPRESSION as the needle will indicate by how much the sensitivity of the amplifier chain has been reduced The extreme left position corresponds to a max imum
20. ent information to be displayed on the modulometer Each position is described below X Position not used RX Indicates the level of the RF signal picked up by the antenna of a QRR receiver if fitted see note SYNCH This indicates the phase shift between the pilot playback signal from the tape and the ref erence signal Synchronism is correct when the needle is stationary PILOT PLAYBACK _ This indicates the level of the pilot signal played back from the tape PILOT FREQ This indicates on the 4 to 4 scale of the modulometer the frequency deviation as determined by the QFM frequency meter circuit if fitted between the pilot signal being recorded or played back and the 50 60 Hz reference LEVEL The modulometer will indicate the level of the direct or of the recorded signal on the decibel scale BATT RESERVE Indicated on the lower scale the bold line shows the supply voltage reserve the lower limit at the extreme left of the bold line represents 11 V VOLT CELL This is a battery check indicating on the V CELL scale of the meter the Volts per cell of the batteries COMPRESSION Compression reading in decibels on the ALC compression scale when switch 10 is in the AUTOMATIC position MOT This measures the motor current Maximum deviation 250 mA BIAS This indicates the record bias level on the V CELL scale NOTE The QRT QRR radio transmitter and receiver accessories are no longer manufactured 13 FILTER SWITCH
21. er 4 pp 34 35 Extemal Power Supply On the right side of the machine there is a 6 pin Tuchel type T 3403 connector marked POWER PACK The corresponding plug is the T 3400 1 The connections are as follows pin 1 Battery negative pin 2 Chassis positive pin 3 Pilot playback output pin 4 Speed correction signal input pin 5 Negative external supply pin 6 10 V stabilized output 1 5 OPERATION On the right side of the front panel is the main function selector which determines the mode in which the Nagra works By putting it into the position TEST all the circuits are powered but not the motor If the meter switch on the upper right side of the modulometer is switched to the BATT RESERVE position the needle of the mod ulometer indicates that the Nagra is powered if this is not the case see Power Supply in this manual With fresh batteries the needle will not advance to more than half way up the scale It only reaches the extreme right of the scale with an external power supply After checking the power supply put the meter switch to the LEVEL position recording or modulation level A microphone can receive sounds of a very variable intensity The tape must be recorded as fully as possible but without the high frequencies passing a level called the saturation level The modulometer indicates the level of modulation The needle can deflect up to the mark Max on the right of the scale but should not
22. er depending on the microphone preamplifier which is fitted or as a line input via the QCE cable The Nagra 4 2 also contains a switchable limiter a built in loudspeaker and an internal reference generator for line up and calibration purposes Optionally the machine may be fitted with the NEOPILOT pilot option The machine may also be powered from either an external supply ATN 3 or internal batteries The 4 2 may also be used with the QGB 10 real adaptor to allow the use of larger reels for longer recording and playback 23 24 2119 26 27 2829 20 30 11 315 34 22 32 25 10 ll 12 13 14 15 16 17 18 19 TAPE DIRECT SWITCH line and phones TAPE DIRECT snap switch POWER SELECTION SWITCH external bat teries MAIN FUNCTION SELECTOR six position rotary PINCHWHEEL LIFTER stop test only LEVEL CONTROL mic input 2 LEVEL CONTROL mic input 1 REFERENCE OSCILLATOR push button LINE amp PLAYBACK POTENTIOMETER MANUAL AUTOMATIC SELECTOR LID CATCH MODULOMETER MODE SELECTION SWITCH FILTER SWITCH MODULOMETER PILOT INDICATOR SPEED AND POWER INDICATOR HEADPHONES OUTPUT HEADPHONES VOLUME CONTROL REEL FIXING NUT 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 SPEED AND EQUALIZATION SELECTOR MOBILE TAPE GUIDE PINCH ROLLER REWIND AND FAST FORWARD SWITCH TAPE REELS TENSION ROLLERS ERAS
23. gain the extreme right to a reduction of gain or compression of approximately 30 dB When a signal whose amplitude is sufficient for the maximum recording level to be exceeded arrives from the microphone the Automatic Level Control will instantaneously reduce the gain to avoid over modulation similar to the limiter If the signal is short the Automatic Level Control concludes that it is accidental and forgets it rapidly i e it returns to its previous sensitivity On the other hand a longer signal is considered useful The sensitivity is therefore memorized and maintained This avoids the increase of background sound level between words It can happen however that an interfering signal is long and thus results in a long sensitivity reduction To avoid this the Automatic Level Control has a circuit of rapid recovery which enters into action if the level remains at less than 10 dB for about 1 1 2 seconds Therefore if a long and loud noise upsets the recording the recorder can be reset to its normal sensitivity by keeping quiet for 1 1 2 seconds Experience has shown that the Automatic Level Control allows an absolutely automatic recording to be made for reporting interviews etc and of a quality which is difficult to attain with manual control Measurement of Signal Level The Nagra 4 2 is equipped with a device for measuring the signal level Normally this is a modulometer but a VU meter is available on special request The meter is
24. he two possible PLAYBACK positions either with or without loudspeaker The signal from the tape is now available on line output banana output connectors 45 46 on the right side of the recorder If line and phones switch 1 is in the TAPE posi tion the signal is fed directly to the line outputs with no possibility for adjustment However if it is in the DIRECT position then the output may be adjusted with the LINE AND PLAYBACK potentiometer The frequency response may also be modified using FILTER switch 13 Working with Headphones If headphones are to be used they can be plugged into jack socket 17 The level of the headphones may be adjusted using potentiometer 18 In record the signals can be monitored either off tape or directly depending on the position of the line and phones switch NOTE When the machine is in the TEST position the headphones output is always fed with the DIRECT signal The headphones output will accept a 1 4 stereo J ack connector and can be used with headphones having an impedance from 50 Q to 600 Q During playback the headphones may be used for monitoring In the position TAPE the signal coming from the tape can be heard In the position DIRECT a mixing of the signals coming from the microphones and from the tape can be heard The mixing of these signals can be controlled by means of the potentiometers MIKE 1 MIKE 2 and LINE AND PLAYBACK To listen to the recording on an exte
25. if the frequency of the pilot signal is incorrect on condition that the QFM frequency meter cir cuit is installed b if the pilot signal does not reach the pilot head on condition that the QSLI synchronizer circuit is installed This is indicated in the position TEST of the main function selector When the Nagra is in playback this indi cator will only show a white segment when a pilot signal is being played back from the tape and another pilot signal is being fed from outside It one of these two signals is missing the indicator will remain back This is very important when using the QSLI Intemal Synchronizer optional accessory QSLI This device has two functions a It measures the amplitude of the playback pilot signal on the tape With the meter switch in the position PILOT PLAYBACK the meter indicates the amplitude The normal value should be between 1 and 2 V on the lower middle scale b It can modify the tape speed of the Nagra in order to render the playback pilot signal synchronous with a pilot signal coming in on the PILOT socket For this speed correction to take place the Nagra must be switched to LOUDSPEAKER PLAYBACK and the PILOT indicator should show a white cross The white cross is only shown if the external pilot reference signal is correct and a pilot sig nal is played back from the tape When meter switch 12 is in the SYNCH position the meter is connected to the QSLI and shows the differ ence of pha
26. justment and will prove that synchronization is correct Speed Varier QSV 2 This is an external accessory for the Nagra 4 2 It is plugged into the ACC socket 39 on the left side of the recorder It enables the speed to be varied manually up to 12 The QSV 2 is used for the following applica tions a To transfer a tape whose pilot signal originated from a camera the speed of which was out of tolerance The QSLI synchronizer allows the automatic correction of speed errors up to 2 It is not unknown for cameras to have a speed error greater than this tolerance The speed varier allows the offsetting at the average speed which will then be corrected by the synchronizer in the normal manner Naturally under these conditions the tone of the sound will be altered but this is inevitable b Transfer of a tape whose pilot signal is interrupted A very convenient method of indicating the start marks or end of takes as well as the take identification is by short interruptions of the pilot sig nal During these interruptions the slaving between the Nagra 4 2 and the film recorder is sup pressed It is important that the speed change during the suppression is not brutal otherwise audi ble wow will be heard To avoid this it is sufficient to make approximate correction with the aid of the speed varier and to allow the synchronizer to make a final adjustment to ensure the slaving This can be done as follows Method A 1 Play back the tape
27. me remove the batteries as a corrosive liquid can leak from discharged batteries Direct and Tape Chains General Signals coming from the microphone s line and mixer inputs once they are amplified fiftered controlled and mixed form the DIRECT signal which will be recorded on the tape The signal played back from the tape gives after amplification and equalization the TAPE signal During recording the TAPE signal is that which has already been recorded on the tape and therefore is not that which is being recorded The modulometer measures the level of the DIRECT signal It is operational even in the absence of a tape On the other hand there will be no TAPE signal in this case When the Nagra is in playback the level control potentiometer LINE AND PLAYBACK is used to adjust the TAPE signal The DIRECT signal may therefore be made up of the input signals plus the playback signal This allows for example the superimposition of a commentary to the signal being played back from a tape On the other hand the TAPE signal will always be exclusively the playback signal from the tape The line output amplifier which also feeds the headphones can be connected either to the TAPE signal or to the DIRECT signal the choice being made by the LINE AND PHONES switch on the front panel The loud speaker amplifier is only fed from the TAPE signal Acoustic feedback therefore cannot be produced even if the microphones
28. or control input control voltage 4 to 14 V or switching on of QRR receiver by connecting to ground 3 XTAL Internal crystal pilot generator output 50 60 Hz 4 PILOT IN Pilot signal input impedance 5 kQ Input level 0 5 25 V 45 LINE OUTPUT The line output of the Nagra 4 2 is on the right hand side of the recorder The load impedance should be equal to or greater than 600 Q When the LINE AND PHONES switch is in the position TAPE the line out put voltage is 4 4 V into 600 Q while playing back a tape recorded at 0 dB The Nagra 4 2 can record at a level 4 dB higher than this thus the maximum line output voltage will be 7 V Unloaded these voltages will be 10 greater The line output uses two 4 mm banana sockets It is the secondary of a transformer and is floating A banana socket connected to the chassis is available beside the line output sockets 46 GROUND banana socket 47 LOUDSPEAKER 48 POWER PACK 6 pole connector for external power supply and pilot signal output 1 BATT Negative pole of battery compartment 2 BATT Positive pole of battery compartment 3 PILOT PLAYBACK Pilot playback output 4 SPEED CORRECTION Tape speed correction input 5 EXTERNAL 12 to 30 Input for external power Supply 12 to 30 V negative pole 6 10 R 10 V stabilized voltage output during record max 100 mA 49 FIXTURE FOR CARRYING STRAP HANDLE 50 CASE FIXING SCREW 51 PLATE SHOWING RECORDIN
29. ossible to optimize the equalization in the second position LN for a different tape Loading a Tape on the Recorder Select STOP then release the tape path from the heads guides and capstan shaft by pulling lever 32 for ward until it comes to a complete stop Remove the spool retaining nuts and place a reel of tape on the left turntable with the loose end of the tape coming from the left side of the spool Pass the tape around the left guide roller and across in front of the heads and around the right guide roller Attach the end of the tape to the empty spool on the right turntable Replace the two spool retaining nuts and close lever 32 until it reaches its original position thus putting the tape into contact with the heads NOTE Itis important to lower the head shield before loading a tape otherwise the tape may pass behind it and thus not be in contact with any of the heads When the tape has been loaded and lever 32 has been restored to its original position the shield may be lifted in front of the heads Recording The Nagra 4 2 can make a recording using either microphones or a DIRECT line input signal Recording with Microphones When using microphones connect them to the two XLR type connectors on the left side of the recorder If the QPAU T QPU T microphone preamplifiers are installed in the recorder check that the switches corresponding to each of the microphone inputs are in the correct position for the type of
30. put connector 41 on the left side of the recorder Set main function selector 4 to the TEST position and adjust the level of the incoming signal on the modulometer by means of potentiometer 9 marked LINE AND PLAYBACK Finally switch the main function selector to one of the two RECORD positions to start the recording When the recording is completed select STOP Fast Forward Rewind To rewind a tape put the main function selector in the STOP position and open the pinchwheel gate by using operating lever 32 then select TEST and rewind the tape by means of toggle switch 23 located on the top left front comer of the top deck When the tape is fully rewound always place operating lever 32 back in the fully closed position this will pre vent a flat portion being made on the capstan 0 ring To wind a tape fast forward use switch 23 as for rewind However it is not necessary to open the pinch roller gate The FAST FORWARD position of the toggle switch is only active when the main function selector is in the PLAYBACK with loudspeaker position This is done to prevent accidental winding of the tape during recording While winding the tape fast forward the audio on the tape will be heard through the internal loudspeaker To avoid damage to the loudspeaker use volume control 42 to decrease the level Playing Back a Recorded Tape Rewind the tape as explained above then set main function selector 4 to one of t
31. rent tape types For best quality recordings the 15 ips speed is recommended For normal recordings the 7 1 2 ips speed is available The 3 3 4 ips speed is available for those cases where the length of recording time of the tape is more critical than the actual quality of the recording 21 MOBILE TAPE GUIDE 22 PINCH ROLLER 23 REWIND AND FAST FORWARD SWITCH REWIND is possible with main selector 4 in any position other than STOP assuming pinch roller lever 32 is in the fully open position FAST FORWARD is possible only with main function selector 4 in the PLAYBACK with loudspeaker position and pinch roller lever 32 fully engaged The central position of this switch is OFF and this is the position that the switch should be in whenever the machine is not required to spool Keeping it in this position will prevent accidental spooling of the tape when opening the pinch roller gate or playing back a recorded tape through the internal loudspeaker 24 amp 34 TAPE REELS The 4 2 can be used with reels up to a maximum diameter of 5 127 mm with the plexi glass lid closed or up to 7 178 mm with the lid open However it the QSET option is fitted to the machine the 7 178 mm reels my be used with the lid closed If it is necessary to use reels of up to 10 254 mm then the QGB large reel adapter may be used 25 amp 33 TENSION ROLLERS These two rollers keep the tape tension constant and ensure correct tape h
32. rnal amplifier loudspeaker installation connect it to the Line Output on the right of the recorder This output receives the same signal as is transmitted to the headphones Loudspeaker sig nals should not be allowed to feed a microphone Under these conditions the signal passes from the loudspeaker to the microphone which retransmits it producing a howling known as the Larsen effect acoustic feedback To avoid this effect the LINE AND PHONES switch should be placed in the position TAPE or the poten tiometers MIKE 1 and MIKE 2 turned down To playback in the headphones or to an external installation the position PLAYBACK of the Main Function Selector should be chosen The internal loudspeaker is thus disconnected Precautions The pinch wheel is automatically disengaged in the position STOP of the Main Function Selector This enables the Nagra to be stored with the Pinch Wheel and Tape Guido Control Lever in the closed position If this lever is in the disengaged position the lid of the recorder cannot be closed Do not store the recorder with the Main Function Selector in any position other than STOP as this will cause a flat to be formed on the pinchwheel and this will cause Wow and Flutter problems during future uses To avoid the accidental discharge of the batteries put the POWER switch into EXTERNAL thereby disconnecting the internal batteries if installed If the recorder has to be stored for a long period of ti
33. se between the external pilot signal and the playback pilot signal from the tape Thus if the signals do not have exactly the same frequency and phase the needle will oscillate This can be seen on PLAYBACK without the loudspeaker One complete oscillation left right left every 2 seconds corresponds to a speed error of 1 which can be corrected by the QSLI By putting the main function selector in the LOUDSPEAKER PLAYBACK position the QLSI is switched on and the needle should be stationary If it continues to oscillate then the frequency exceeds the synchronizing capacity of the QSLI If the Nagra is equipped with frequency meter circuit QFM and the needle is stationary and it the pilot indica tor shows a white cross synchronization is practically certain There is one exception however it the playback frequency from the tape is grossly incorrect e g 100 Hz instead of 50 the needle will not be able to follow the beat and will remain stationary in the centre of the dial If this is suspected switch to PLAYBACK The needle should oscillate If need be upset the tape speed by block ing the left side tension roller momentarily If the needle remains in the centre the recorded pilot signal is incorrect The speed varier QSV 2 is very useful in these cases In attempting to adjust the speed on slaved playback the QSLI has to adjust itself in order to prevent the speed varier from operating The needle of the meter will show this ad
34. sition for long periods of time as this may cause a FLAT on the capstan shaft 0 ring 33 TAPE TENSION ROLLER OR TIMER see 25 34 TAKE UP REEL see 24 Positions 36 to 49 see CONNECTORS 1 3 CONNECTOR 38 36 37 39 4140 42 43 49 36 MIKE 2 Input CCIR NAB 1 Input signal Ground G p g 2 3 Balanced signal Input Q 37 MIKE 1 input Identical to No 36 above NOTE The microphone inputs are convertible into symmetrical and floating line inputs by installing in place of the microphone preamplifiers preamplifiers type QPM 6 and using the corresponding potentiometer to control the input level 38 RX Antenna input for QRR receiver 39 ACC accessories 1 No connection 2 Ground O 3 Line input current drive Minimum source impedance 47KQ Current for obtaining 0 dB at maximum sensitivity 3 73 pA 4 Tape speed correction signal input 5 No connection 6 10 V stabilized voltage 40 MIXER For connection to external mixing console connector type T 3478 corresponding plug T 3475 1 41 LINE INPUT Input with fixed sensitivity 560 mV to obtain 0 dB input imped ance 9 kQ 2 5 Vpp to obtain 4 dB 10 V stabilized voltage maximum current 50 mA Noise level lt 5 uV rms Direct amplifier output minimum load impedance 10 kQ output voltage 560 mV at 0 dB This is a monitoring signal to be fed back to the mixer Unstabilized negative supply voltage Av
35. ton is pressed a composite 1 1 kHz signal with a 10 kHz 9th harmonic at a level of approximately 8 dB is injected into the DIRECT chain of the recorder The modulometer will show 8 dB It is useful to record a short burst of this signal at the beginning of each reel of tape so as to enable the level of the playback chain to be accurately calibrated before the real recording is made This also permits adjustment of the record head azimuth in the field without test equipment At this point the subject of print through should be mentioned After a certain period of time a recording may be copied at reduced level onto adjacent turns of a tape on a reel This produces a perceptible echo during the silences pro ceeding or following a strong sound It is thus recommended to leave a pause of two or three turns of tape after recording the REF signal 9 LINE amp PLAYBACK POTENTIOMETER This potentiometer is used to adjust the line input level when using the machine to record a signal from line input 41 10 MANUAL AUTOMATIC SELECTOR This switch allows selection of the sensitivity adjustment of the microphone inputs In the MANUAL position the sensitivity is adjusted by means of potentiometers 6 and 7 In AUTOMATIC position this gives ALC automatic level control to mic input only and in position 2 to both mic inputs 11 LID CATCH 12 MODULOMETER MODE SELECTION SWITCH This is an eleven position rotary switch allowing differ
36. wn for both the film camera and the Nagra then the two can remain in perfect synchronization throughout the tape To obtain a film with a synchronous sound it is necessary to keep the image and the sound continually slaved to one another The acceptable tolerance is in the region of 40 m Sec 2 2 OPERATION Recording a Pilot Signal A pilot signal can be recorded when recording either a line input signal or when using microphones Recording the Intemal Crystal For the 4 2 to record its own pilot signal the QGX 3 crystal generator must be fitted to the machine This circuit is located on the left side of the battery compartment inside the machine It has two operating frequencies 50 or 60 Hz Check by means of the switches on the circuit that the correct frequency has been selected Then switch the main function selector to the TEST position Pilot indicator 15 on the top right side of the front panel should show a white segment If this is not the case then check that the pilot crystal shorting plug is locat ed in pilot socket 44 This jumper plug is like a blank screw with the letters XTAL marked on it If this is installed and the rotary indi cator does not show a white segment then check that the machine is correctly powered and that power selector 3 is in the correct position with respect to the supplied source If this is all correct but the indicator remains black then consult your nearest Nagra agent Once the indicator shows
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