Dolby Laboratories SR 280 User Information Download | Manualshive

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Summary of Contents for SR 280

Page 1: ...I DolbYSR Cat No 280 Spectral Recording Module User Information...

Page 2: ...purpose During the warranty period Dolby Laboratories will repair or at its option replace components which prove to be defective provided the unit is shipped prepaid to the manufacturer directly or...

Page 3: ...amiliarity with Dolby A type noise reduction and interface frames Important Note The Cat No 280 spectral recording module is both pin and level compatible with the Cat No 22 A type module In most case...

Page 4: ...n pink noise generator in the module applies bursts of noise Dolby Noise at a calibrated level to the recorder The signal is used at the head of a tape to identify the use of Dolby SRI and to assist i...

Page 5: ...el to CCIR ARM Stability noise level System is highly stable does not require 93 dB clipping level to CCIR Rec 468 2 routine alignment no adjustable internal weighted noise level controls 105 dB clipp...

Page 6: ...se 3 1 3 2 Auto Compare 3 1 3 3 Auto Compare Control 3 2 3 4 Auto Compare Metering 3 2 3 5 Auto Compare Synchronization 3 2 3 6 Dolby Tone and the Cat No 280 3 3 SECTION 4 SYSTEM ALIGNM i N I 4 1 Gene...

Page 7: ...her such as in the Model 362 a special packaging adaptation of the Cat No 280 has been developed the Cat No 280 L This long but thin adaptation extends the Dolby SR circuits forward of the front panel...

Page 8: ...e required for one channel of simultaneous record and playback operation The Auto Compare feature can be fully operational during both record and playback Model 361 The Model 361 is designed for chang...

Page 9: ...e are some electrical incompatibilities with the Cat No 230 carrier card The Cat No 431 due in late 1986 will fit both the SP and XP multi track units This module will be a plug in replacement for the...

Page 10: ...nual for information regarding connections etc The Cat No 280 module consumes roughly the same amount of power as the Cat No 22 A type module and therefore has the same cooling requirements It is impo...

Page 11: ...tinue to operate correctly The tape will always be properly encoded or decoded regardless of the position ofthe configuration switch Cat No 280 Indicators YELLOW indicator Dolby Noise ON The yellow in...

Page 12: ...cators The reference pink noise is available at the edge connector for other uses Additionally a terminal has been provided that will allow Auto Compare circuits to be synchronized The user is encoura...

Page 13: ...y Level This lower level is compensated by gain in the calibration meter amplifier so that Dolby Noise will read on the Dolby Level dot in the center of the calibration meter In other words the level...

Page 14: ...de or changeover operation The mode of operation is selected by the rear switch on the module These specific differences are discussed in Section 5 Practical Operation 3 4 Auto Compare Metering The ca...

Page 15: ...have been recorded with the tape recorder set up for a different reference flux level the Play Cal on the recorder or sometimes more conveniently the input potentiometer on the interface frame will h...

Page 16: ...formance of the recording system is limited by the microphone pre amplifiers or the ambient noise level found at the recording location so such attention to precise matching is unwarranted The basic C...

Page 17: ...ference level from the console to align the record aspects of the Dolby interface frame With the Model 361 this has been already accomplished with the steps above 6 Adjust the record sensitivity of th...

Page 18: ...Dolby Noise will still be generated and metered at Dolby Level the center dot Regardless of the specific procedure used to set reference level through the Dolby interface frame Dolby Noise must be se...

Page 19: ...the Model 361 this has been already accomplished with the steps above 6 Adjust the record sensitivity of the recorder to give a Dolby Level reading on the Dolby frame calibration meter 7 With the Dol...

Page 20: ...nces in the detailed alignment procedure and the operation ofthe Auto Compare circuit between the Model 360 Model 361 and M Series units therefore a separate procedure is provided for each Please refe...

Page 21: ...e record unit to obtain Dolby Level on the calibration meter The output potentiometer on the record unit is then adjusted to obtain reference level at the recorder 5 2 Auto Compare in the Model 360 Wh...

Page 22: ...p Note A Cat No 280 modules before serial number 456 have the playback meter signal connected to the output of the Auto Compare switch Boards tamped 456 and above have the calibration meter connected...

Page 23: ...tion and the general alignment procedure for the 360 Series followed The console should be connected through to the recorder using the Line In and To Recorder connections on the record unit and the RE...

Page 24: ...l lpe To Norm 11 Monitor 361 1Check l lpe R Decode f To Norm ll Monitor Meter 361 1 Che k 1dPf I 1 To _ Nurmli Monitor 361 Tclpe 1Chf r e To Nnrm ll Monitor Mptn Note A Cat No 280 modules before seri...

Page 25: ...Recorder connections on the record channels and Rec Rem triggers linked so that the channel is locked into encode or record operation The Line In and the To Rec on the Cat No 44H version only potenti...

Page 26: ...k Pink NOise Gen DOLBY NOISE CAL PLAY Dolby M Series NOise TAPE RECORDER From 1 Chpck Tape z j IPf Q O I Line I To From I To Input Recorder Recorder I Monitor I I Normdl _ e Pink NOise Gen Note A Cat...

Page 27: ...Spectral Recording Process Dolby Laboratories Inc San Francisco and London S86 6825 RMD February 24 1986 Technical Aspects...

Page 28: ...dvantages arising from the use of multi level stages including action compounding for good spectral discrimination accuracy and reproducibil1ty low distortion and low overshoot The thresholds used are...

Page 29: ...A design philosophy used in the development of the new system is that the best treatment of the signal is the least treatment The design goal for the encoder is to provide a predetermined fixed gain f...

Page 30: ...effective on a continuous and frequency by frequency basis For exampleJthe output from a given high frequency stage will typically be from the fixed band for frequencies up to the dominant signal comp...

Page 31: ...law then it is unnecessary to continue the limiting as the signal level rises Rather the level of the side chain signal can be allowed to rise as the input signal rises stabilizing at some significan...

Page 32: ...distortion is minimal Under relatively steady state but nonetheless changing signal conditions the overshoot suppression effects are gradually phased out with increasing signal levels this action furt...

Page 33: ...two recording processes are similar at high levels SR will typically have several dB of further soft clipping headroom available At very low signal levels with increased monitor gain the audible sign...

Page 34: ...e dominant signal component the SR circuit employs the steepness enhancing effect that arises from the use of cascaded stages The low frequencies have two stages of steepness compounding At high frequ...

Page 35: ...gnal at high recording levels is significantly improved Aotjsaturatjoo aspects The antisaturation effects of SR are maintained down to fairly low levels about 15 dB below reference level The result is...

Page 36: ...s allows the tape replay gain to be set correctly using the meter in the decoder unit Most problems in the studio use of A type noise reduction and indeed analogue recording in general can be traced t...

Page 37: ...rame During calibration the meter circuit in the frame is fed by a band limited 200Hz 4 kHz Auto Compare signal from the module Band Hmiting reduces the effect on the meter reading of frequency respon...

Page 38: ...xed Band HF Sliding Band Fixed Band LF LF Anti saturation QD Mid Level Stages Sliding Band 1 Fixed Band HF Sliding Band Fixed Band LF r LF De Anti saturation Low Level Stage Sliding Band Fixed Band HF...

Page 39: ...9 volts DC therefore an external coupling capacitor will be necessary Pin C External Auto Compare Synchronization In the record mode the Dolby Noise mark Cfnick generator on the Cat No 280 module norm...

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