Universal Audio 1178 Operating Instructions Manual Download Page 1 | Manualshive

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Summary of Contents for 1178

Page 1: ... Vx i T ro I S 4 CJ T C model 1178 DUAL PEAK LIMITER n nr n RECORDING ELECTRONICS INDUSTRIES I LJ II I 84 OSANFERNANDaRD SUNVALLEY CAllFOIINIA9l352 8I8 767 I000 PDg ...

Page 2: ... SC 2 SECURITY COVER 9 SECTION III OPERATING INSTRUCTIONS 3 1 GENERAL DEFINITIONS 10 3 2 INITIAL SETUP H 3 3 PERFORMANCE CHECK 11 3 3 1 INPUT OUTPUT SIGNAL LEVEL 11 3 3 2 GAIN REDUCTION CHECK 12 3 3 3 STEREO TRACKING 12 3 4 APPLICATION 12 3 4 1 CONTROL SETTINGS 12 3 4 2 EFFECTS OF COMPRESSION RATIO 13 3 4 3 EFFECTS OF THRESHOLD 13 3 4 4 EFFECTS OF ATTACK TIME 13 3 4 5 EFFECTS OF RELEASE TIME 14 3 ...

Page 3: ...0 5 2 REPAIRS AND WARRANTY 20 5 3 INTERNAL SERVICE ADJUSTMENTS 20 5 3 1 POWER SUPPLY 21 5 3 2 Q BIAS ADJUSTMENT 21 5 3 3 GR METER ZERO AND TRACKING 22 5 3 4 COMMON MODE REJECTION 22 5 4 IN CASE OF DIFFICULTY 22 5 4 1 GENERAL 22 5 4 2 PRECAUTIONS FOR TROUBLESHOOTING 23 5 4 3 VISUAL TEST 24 TROUBLESHOOTING TABLE FIG 5 1 24 5 5 PC BOARD CLEANING 26 5 6 CLEANING THE LIMITER 26 SECTION VI APPENDIX FIGU...

Page 4: ...ked together such that the audio signal with the larger peak to peak amplitude causes the same amount of gain reduction in both channels On the other hand when switched to single mode operation the two limiters process the signals independently This provides the user with exceptional flexibility in operation The Model 1178 was designed to have performance characteristics similar to the single chan...

Page 5: ...g devices distortion of low frequency peaks increases with faster release time SIGNAL TO NOISE RATIO Greater than 81 dB at threshold of limiting 30 Hz to 15 kHz ATTACK TIME Less than 20 microseconds for 100 recovery adjustable to 800 microseconds with front panel control RELEASE TIME 50 milliseconds minimum 1 1 seconds maximum for 63 recovery Adjustable with front panel control Input Level at Rela...

Page 6: ...ent limiters In the STEREO position the gain reduction amplifiers of the two channels are linked together and the maximum limiting in one channel causes an equal amount of limiting in the other channel The compression ratio attack time and release time are always identical in both channels COMPRESSION RATIO Switch selectable with four interlocking pushbuttons METER FUNCTION Three interlocked pushb...

Page 7: ...ed 483 X 89 mm rack panel Depth behind panel 203 mm 19 x 3 1 2 x 8 Panel is 3 18 mm 1 8 brushed clear anodized aluminum in 2 shades Chassis is cadmium plated steel 5 kg 11 lb 6 6 kg 14 5 lb Model 301 XLR QG Adapter for signal input and output Model SC 2 Security Cover Rear chassis barrier strip for input and output Power through 3 wire lEC style connector 4 ...

Page 8: ...NTAL CONSIDERATIONS The system will operate satisfactorily over a range of ambient temperatures from 0 C to 50 0 32 F to 122 F and up to 80 non condensing relative humidity If the system is installed in an equipment rack with high heat producing equipment such as power euntiplifiers adequate ventilation should be provided in order to assure longest component life Also while circuitry susceptible t...

Page 9: ... the line cord specifies otherwise the Model 1178 was shipped ready for operation with nominal 115 VAC power mains In order to change this for nominal 230 V 50 Hz or 60 Hz slide the VOLTAGE SELECTOR switch on the rear panel to the 230 position The voltage is visible in a window next to the switch slot Be sure to change the fuse to the correct value 1 8 amp slo blo when changing to 230 V operation ...

Page 10: ...ED OUTPUT CIRCUITS FIGURE 2 2 CONNECTING THE MODEL 1178 WITH UNBALANCED INPUT AND UNBALANCED OUTPUT CIRCUITS With a balanced input and unbalanced output or vice versa use the appropriate conhections suggested by each of the above diagrams No special switching or transformers are needed ...

Page 11: ...se with various source impedances Most modern audio systems therefore utilize amplifiers and other active devices which have very low output impedances and high lOK to 50K input impedances These products may thus be cascaded operated in tandem or many inputs may be connected to a single output of a proceeding device without regard to impedance matching Switching patching etc is simplified because ...

Page 12: ...ip This allows simple mounting of the Model 301 and adapts the limiter to signal cables fitted with XLR QG termination 2 7 2 SECURITY COVER SC 2 An optional Security Cover is available to cover all operating controls of the Model 1178 and to protect against any inadvertent misad justment of critical settings 9 ...

Page 13: ...he degree to which the dynamic range is restricted The relationship of input level change versus output level change is called the Compression Ratio If for example an increase of 8 dB input signal level should cause the output to increase by 2 dB this would represent a 4 1 compression ratio Although no strict standards exist amplifiers with compression ratios of up to 8 1 are typically considered ...

Page 14: ... adjustments are discussed in more detail in the section on application 3 2 INITIAL SET UP After the Model 1178 has been installed and is connected to both the signal source and the succeeding equipment according to Section II power may be turned ON Set the controls as follows Input Output Attack Release Compression Ratio Meter Function Peak Avg CCW Half rotation Fully CCW switch to OFF position H...

Page 15: ... position adjust the Input controls until the same amount of GR is indicated on each VU meter for example 5 dB Select the 4 dB meter function and adjust the Output level controls for the same indication on both meters for example 0 VU Switch the mode switch to STEREO and check the tracking between the two meters to remain within 1 dB 3 4 APPLICATION 3 4 1 CONTROL SETTINGS Since all important parem...

Page 16: ...ations When the input is adjusted so that the average signal level is above the threshold all the time then the entire program material will be compressed Monitoring the amount of gain reduction is made easy when the meter function is switched to the GR mode 3 4 4 EFFECTS OF ATTACK TIME Fast transients and high frequencies with large peak to peak amplitudes can only be limited or compressed if a f...

Page 17: ...in reduction caused by a large amplitude and the dynamic range of the passage which follows is strongly affected If the gain reduction continues through a soft program section it may make this section inaudible because it too will be reduced in gain Also short dynamic changes will be ignored due to the continuous high level of gain reduction The most desirable release time setting for particular p...

Page 18: ...sult Here are some additional tips On live program material the fastest attack time possible will afford the maximum protection against overload but will cause some alteration of the sound On pre recorded tape disc or film slower attack time may be used to maintain a high average level For program material containing relatively little low frequency energy the release time may be fast thereby incre...

Page 19: ...level contribute no apparent degrada tion to the dynamic range which might subjectively affect the artistic value of the program and at the same time maintain the individual quality of all sounds regardless of their starting transients 3 6 STEREO OPERATION When stereo signals are processed the balance of the two audio channels is important To maintain a good balance between channel A and channel B...

Page 20: ...he differential amplifier through the Input Level control to an L section consisting of R3 R103 as the series element and field effect transistor Q7A Q7b as the voltage variable shunt element Below the threshold of limiting the FET has a very high resistance During limiting the gain reduction amplifier causes the FET to conduct decreasing its resistance proportionately The Q bias network R12 R13 R...

Page 21: ...39 for 20 1 voltage divider R35 R36 R37 for 8 1 and 12 1 ratios Diode CR7 around the inverting amplifier prevents the output voltage from assuming a negative value During conduction transistor Q3 functions as a current source for the timing capacitor C37 The charging time is variable with R42 which is the Attack Control of the limiter When transistor Q3 is turned off the discharge of C37 occurs th...

Page 22: ... The time constant for the rise and fall of the meter is determined by com ponents C51 R60 and R59 When the meter is switched to gain reduction GR one side of it is biased with network R61 and R62 to read zero when no limiting occurs The positive GR control voltage buffered in IC 7C causes a reduction in potential difference across the meter terminals thus deflecting the needle of the meter downsc...

Page 23: ...tly to the factory with the Number visible on the shipping label Be sure it is well packed in a sturdy carton with shock absorbing material such as foam rubber styrofoam pellets or bubble pack completely filling the remaining space Particular attention should be paid to protecting the controls switches etc Tape a note to the top of the unit describing the malfunction and instructions for return We...

Page 24: ...correctly set and therefore we strongly urge you to MAKE SURE that adjustment is necessary before undertaking the procedure This may most easily be done by applying an input signal 1 kHz 0 dBm with the limiting turned OFF Turn the Output con trol full CW and turn the Input control up until the output reads dBm on an external voltmeter Remove Q7 from the socket on the P C board and observe the mete...

Page 25: ...ut Attack Release Compression Ratio Meter Mode to number 18 on the front panel full CW full CCW switched to OFF position full CW 20 1 GR Apply a signal to the input 100 Hz 10 dB Adjust the Input Level control to achieve 10 dB output level measured with an external AC voltmeter Connect the and COM terminals together and feed a signal of the same input level to this connection and to the GND termina...

Page 26: ...re very vulnerable to damage when accidentally shorted or connected to incorrect voltages Be sure not to short any terminals when making measurements If a probe should slip for example and short out a bias or supply point it will very likely damage IC s transistors or diodes Do not remove any components while the line cord is connected to the AC outlet 23 ...

Page 27: ... Check supply voltages Remove Q7 If signal passes go to problem of full limiting 3 Loose or broken wires between PC board and front panel controls Isolate and resolder 4 Incorrect hookup See Section II Installation 5 Bad amplifier section Repair No limiting 1 Limiting switched OFF Turn Attack control CW 2 Input level is below threshold Increase input signal level 3 Q Bias misad justed Adjust 11 5 ...

Page 28: ...pply Check filter caps Distortion during no 1 Power supply voltage Repair as needed limiting mode 2 Input level too high Adjust 3 Defective output amp Repair Distortion during limiting 1 Cracking sound on attack Attack set too fast or check Q Bias 5 3 2 2 Low frequency distortion Select slower settings of Attack and or Release controls VU meter reads low on 1 Bad meter 1 Replace 4 8 range 2 Switch...

Page 29: ... moisture will be retained for a longer time and cleaning of the board is necessary Disconnect the power cord from the AC mains Prepare a clean ing solution by mixing equal parts of distilled water and isopropyl alcohol Use a new tooth brush or similar stiff bristle brush and apply the mixture to the circuit board Brush vigorously to thoroughly clean the top and bottom of the board and allow the b...

Page 30: ...SECTION VI APPENDIX ...

Page 31: ......

Page 32: ...FIGURE 6 2 MODEL 1178 DUAL PEAK LIMITER SCHEMATIC DIAGRAM 28 ...

Page 33: ...f l Wl r TT PAf K ARH 9 7O I00f lOdB INPUT LEVEL ...

Page 34: ... BV h tbJ DNb BLU RHZ 1 ZSK CIN 1 ATTACK CIW S YEL VIO A iRHS T fc 5VA RELEASE A R4H i k GRN s G RV IWPUT 100 125 VAC 5O C 0 Hi OFk 200 250 VAC SO fcO Ht GR AWIP RATIO SVNITCN BROVMN IN 20N POSITION NEVER BIN ITCVi SViDINN IN R POSITION PEWS AV SVUTTCVl SNOWN IN AVG POSITION RESISTOR NETVJORICS RN I ANO RNS USED IN CRANNEV A AS SVO WN RESISTOR NCTVi ORR S RNZ AND RNN USF D IN CNANNEU B ON INDICACT...

Page 35: ... POE T ON OF MTf CF CONTROL R OB3 IOP J S RfcS r 0 CVY 1 C R TBAC R N6 RMD pOON TO3 P M 7R TO RN 4H CH E 1 8 A 5 B POE EOO 250 V C I M A 5 B FOR 100 125 VAC T3 t 2 2Bfe 0 MPUT AOO 25 VAC 50 fe0 WT OE 200 250 VAC 50 fe0 Hx NAETER L t V TE DBM TVFE 3E1 TVP EZ O 1 STEREO A B TO C 137 EWM C B PtV J R 6 X V I ECO U7S 0 R6 3 w is 35i oiT iv S7 E eld ia oa E FELTWE VL Q3b o 7 a 35K RtN Ii PER EL0 W78 CU ...

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