DPR-402 User Manual version 3.0
Contents
1. Controls Position PK LIM THRSHLD As required FAST SLOW switch FAST on rear panel The PEAK LIMITER control is calibrated in dBv ref 0 775v and is set to suit the headroom of following equipment Should the red LED indicator remain on other than for occasional peaks the GAIN control should be backed off to reduce the signal to the peak limiter If this produces an unwanted decrease in overall output level then the amount of compression should be increased either by reducing the compressor threshold or by increasing the compressor ratio and then reinstating the gain 15 Applications using the Barrier Strip 15 1 Patching of External Equipment Control Side Chain A very common requirement is to make the threshold of the compressor frequency conscious by inserting a graphic or parametric equaliser into the control side chain The input of the external equipment should be connected to one of the send outputs of the unit and the output of the external equipment connected to one of the return inputs as required Care should be taken to avoid introducing earth loops when the external equipment is mains powered as all inputs and outputs on the barrier strip are unbalanced A signal Ov ground is provided at pins A and J for connection to the screens of one or both of the connecting cables as necessary All external equipment should be capable of operating at general line levels Max 20dBv have unity gain and have high input impedance2. 14 3 De essing Wide with Simultaneous Compression 21 14 4 De ess Wide with Full Dynamic Control 22 14 5 De ess HF with Full Dynamic Control 23 14 6 Peak Limiting 24 15 Applications using the Barrier Strip 24 15 1 Patching of External Equipment 24 15 2 Repatching of the Barrier Strip for other uses and Special Effects 25 15 3 Stereo Linking 27 16 Warranty Information 29 17 Specifications 30 17 1 General 30 17 2 Compressor 30 17 3 De esser 31 17 4 Peak limiter 31 17 5 Notes 31 17 6 Facilities 31 Page 3 BSS Audio D PR 402 User Manual v3 0 1 Compressors and Limiters 1 1 The need for Gain Control The human ear excels in its ability to detect an extremely wide range of sound levels These can range from the quietest whisper to the roar of a jet aircraft When we attempt to reproduce this large range dynamic range of sounds with amplifiers tape recorders or radio transmitters we run into one of the fundamental limitations of electronic or acoustic equipment In some cases such as amplifiers the dynamic range available is quite good However equipment such as tape recorders and radio transmitters have a restricted usable dynamic range W hat limits the available dynamic range of this equipment is its inherent noise floor at the bottom end and the maximum input signal resulting in an acceptable amount of distortion at the upper end The usable dynamic range sits in between these two limits and itis common practice to operate a piece
3. powerful tool for comparing processed signals prior to operating the bypass switch and going on air A further feature of this illuminated switch is to allow coding of each particular channel with a specific number or letter By removing the lens cap with a small screwdriver or your fingernail an appropriate symbol can be fitted This will have particular advantages in situations where more than one DPR 402 is fitted into a control rack 10 8 MODE switch This control switch reconfigures the compressor to insert the built in filters into its side chains so that gain reduction only occurs when certain frequencies are present in the input signal For normal compression this switch will always be in the compress position Please refer to sections 12 2 Broadband De essing and controls and 12 3 HF Only De essing and Controls for a full explanation of this and the applications of de essing Page 14 BSS Audio D PR 402 User Manual v3 0 11 Compression meters 11 1 Below Threshold and Gain Reduction Meter Referring back to section 10 1 Threshold where we discussed the VCA window of operation the five LEDs of the BELOW THRESHOLD meter will give you an indication of the input signal in relation to this window You will notice that the LED marked TH is half on all the time This point represents the threshold point as set by the THRESHOLD control and any signal level that exceeds this LED will start the compressor operatin
4. Controls Position MODE SWITCH Compress THRESHOLD Out RATIO 4 ATTACK RELEASE Auto GAIN 0dB CHN BYPASS In Illuminated DE ESSTHRSHLD Out FREQ PK LIM THRSHLD Out Rotate the THRESHOLD control anticlockwise until the BELOW THRESHOLD meter is fully illuminated and an appropriate amount of gain is indicated on the GAIN REDUCTION meter This operation will be accompanied with a drop in output level as indicated by the OUTPUT METER The output GAIN CONTROL should now be adjusted to reinstate the output level The levels of the uncompressed input signal and the compressed output signal can now be compared on the output meter by operating the METER INPUT switch Final adjustments of the controls can then be made to suit particular requirements including the RATIO ATTACK and RELEASE controls The auto position of the release control provides for a program related operation of the dynamics of the unit and will be accepted for most general purpose applications Should a tighter or looser requirement be necessary then both the attack and release controls can be set individually to suit The experienced engineer will be able to set the compressor controls to near optimum position for any source material with the BYPASS switch out so that the compressor can be dropped into a live performance without disturbance 14 2 De essing The DPR 402 has three modes of de essing available de ess wide with simultaneous compression de ess wide
5. GAIN REDUCTION 9 LEDs to indicate the amount of gain reduction from 3dV to 27dB Display bright up at 30dB of reduction OUTPUT 12 LEDs to indicate output level from 24dBm to 18dBm Display bright up at 21dBm clip DE ESS 2 LEDs to indicate normal and hard de essing PEAK LIMITING 2 LEDs to indicate normal and hard peak limiting Couples channel 1 and channel 2 control signals for stereo operation Indicated on the front panel by an LED INPUT XLR 3 31 or equivalent Balanced OUTPUT XLR 3 32 or equivalent U nbalanced ACCESS POINTS Barrier strip providing control and subtract side chain insertion points including HP and LP filter sends pre emphasis and de emphasis network sends inverse phase sends for expander mode and control side chain DC access point for stereo quad etc coupling and gating Switch selectable 120V or 240V 50 60Hz 15VA AC fuses on the rear of the unit DC fuses located inside the unit Htx W xD 44 5mm x 483mm x 229mm 1U 174 x 19 x 9 4 5kg Packed Page 32
6. combines a program related attack time setting and a two part program related release time setting The two part program dependant release provides A fast release to restore below threshold gain as soon as the transient has passed A much longer following release to avoid rapid gain change effects Page 13 BSS Audio D PR 402 User Manual v3 0 Note that once AUTO time has been selected the attack control becomes inoperative 10 6 GAIN control Because compression is a gain reducing process the output signal level can often be lost The GAIN control is provided to restore this output to normal operating point and provides a calibrated range of 20dB The facility of gain loss provided by this control can be used when required to restore the compression to a point lower than the input signal For example when connecting this output to a high sensitivity input on a following piece of equipment 10 7 BYPASS switch The BYPASS switch enables you to bypass quickly all functions of the DPR 402 by connecting the output directly to the input When the switch is pressed and the lightis on all DPR 402 functions are present on the output signal When the switch is out all facilities are bypassed It should be noted that in the bypass mode the input is still connected to all of the DPR 402 circuitry so that all of the required facilities can be selected and set up This in conjunction with the OUTPUT METER and INPUT SWITCH provides a
7. of equipment ata level that is somewhat below the upper distortion point leaving a margin of safety for the unexpected transient loudness peaks present in program material The safety margin is known as headroom and is generally in the range of 10 to 20dB Lowering the standard operating level to increase headroom helps distortion but moves the average program level nearer to the noise floor thereby compromising the signal to noise performance It therefore becomes apparent that to get the most out of an audio system the standard operating level must be kept as high as possible without risking distortion One solution to this problem is for the operator of the equipment to be continuously monitoring the program and manually adjusting the gain to suit the moment When the program is quiet the gain can be increased and when the program is loud the gain can be reduced However in most types of program there are instantaneous short duration level peaks or transients which would be difficult to anticipate and impossible to respond to in the required time Even a sound engineer with the quickest reflexes could not bring the gain knob or fader down quickly enough The need therefore arises for a fast acting automatic gain controlling device which will track the program material constantly and which will always adjust the gain to maximise the signal to noise performance without incurring distortion This device is called a compressor or limiter
8. sibilance were discussed The DPR 402 provides for this facility in either of two distinct ways Broadband de essing and HF only de essing Under program conditions once the detector detects excessive amounts of frequency it will start to gain reduce the program level as in normal compression Because compression then occurs over the whole frequency range of the program itis called Broadband de essing To make the compressor sensitive only to high frequencies a high pass filter is inserted into the CONTROL side chain insertion Page 16 BSS Audio D PR 402 User Manual v3 0 point with the result that frequencies below the filter cut off point are excluded Once excessive amounts of frequency are detected compression will commence but only on those high frequencies program components that initially caused the compressor to act The type of de essing to be used in a particular situation will depend largely on the program type and whether the input to the compressor is a mix of sibilant sounds and other program material or exclusively the sibilant sound HF only de essing will generally be used when processing a mix of program whereas broadband de essing will be acceptable when processing only the sibilant sound It should be realised that this technique is very different from simple equalisation since equalising a sibilant vocal by cutting high frequencies would result in loss of high frequency content at all times De essing has no effec
9. terminated it is important for personal safety as well as for proper control over the system grounding AC Power Fusing The incoming line power passes through an anti surge T fuse accessible from the rear panel If the fuse blows without good reason refer to section XX Always replace with an identical 20mm x 5mm T fuse rated at either 250mA or 200mA for 240V or 120V settings respectively for continued protection from equipment damage and fire Power ON This is indicated the green ON LED located under the CH IN switches If this LED is not lit when power is connected and the PO W ER switch is depressed 9 Input and O utput Connections Rear Panel Facilities 9 1 Inputs The input is a 10K ohm balanced type on a standard 3 pin female XLR which will accept levels up to 20dBv The or in phase connection is to pin 3 and the or out of phase connection is to pin 2 There is no connection to pin 1 and input cable shielding should be derived from the equipment which is providing the input signal When feeding the DPR 402 from unbalanced sources connect the signal hot to pin 3 and the signal ground to pin 2 Page 10 BSS Audio D PR 402 User Manual v3 0 9 2 Outputs The output connection is a standard 3 pin male XLR Output impedance is less than 1 ohm unbalanced and full headroom is available into any load 600 ohms or greater The signal hot is connected to pin 3 and the ground to pin 2 and pin 1 F
10. the European Union You should include a statement listing the faults found The unit s serial number must be quoted in all correspondence relating to a claim We recommend that you record your purchase information here for future reference Dealer Name Dealer Address Post Zip Code Dealer Phone No Dealer Contact Name Invoice Receipt No Date of Purchase Unit Serial N umber In keeping with our policy of continued improvement BSS Audio reserves the right to alter specifications without prior notice The DPR 402 was designed and developed by BSS Audio Hertfordshire England Phone 44 0 1707 660667 Fax 44 0 1707 660755 W orld Wide Web address http www bss co uk Page 29 BSS Audio 17 Specifications 17 1 General Input Impedance Input Headroom Input CMMR O utput level Output Impedance Output Gain Frequency Response Noise Distortion Cross Talk 17 2 Compressor Threshold Range Compressor Ratio Maximum VCA Range Attack Time Release Time AUTO TIME Constant D PR 402 User Manual v3 0 10k ohm balanced or unbalanced gt 20dBv Better than 50dB 30Hz 20kHz Typically 65dB at 1kHz gt 20dBv into 600 ohms or greater lt 1 ohm unbalanced 20dB continuously variable 1dB 25Hz to 20kHz Ultrasonic filter 3dB at 30kH z Equivalent input noise lt 86dBv 22Hz to 22kHz lt 82dBv CCIR weighted Unity Gain 10dBm output below thres
11. the threshold level that in figure 2 1a will be more affected than that in figure 2 1b 10dB 10dB odB odB ETY fe ee eee Threshold Od Be yO ye crate Theeshold Figure 2 14 Figure 2 1b Page 5 BSS Audio D PR 402 User Manual v3 0 Assuming that all other controls on both channels are set identically with gains equalised the processing effect on these signals is shown below 10dB 10dB 10dB 10dB Figure 2 2a Figure 2 2b It is immediately apparent that there is a large difference between these two signals in relation to their dynamic range and the signal processed in figure 2 2a is said to have been compressed whereas the signal in figure 2 2b is said to have been limited Furthermore it is interesting to note that by comparing the input and output waveforms for the compressed mode the quietest portions of the input signal have been effectively raised in level whereas the loudest portions have been effectively decreased in level The net effect therefore is for both ends of the dynamic spectrum to be pushed or squeezed towards each other This squeezing effect of compression is important to remember and provides a major difference between compression and limiting Compression and limiting differ further in one other important aspect that of the dynamic time settings for attack and release For compressors a slow attack and release time is generally used in order to keep the overall output signal within a s
12. will not normally be required if the wiring is short unless there are strong local interference fields present Page 27 BSS Audio D PR 402 User Manual v3 0 In this mode it is important that the compressor controls are set identically for all channels Improved Stereo Coupling In this mode only the controls on Channel 1 compressor will be required to control both channels as the control signal for channel 1s VCA is used to drive that on channel 2 This gives excellent stereo matching without the need to adjust both sets of compressor controls Two 10k ohm watt 1 resistors are required to sum the left and right signals into channel 1 CONTROL S C RETURN input Page 28 BSS Audio D PR 402 User Manual v3 0 16 Warranty Information When sold to an end user by BSS Audio or a BSS Audio Authorised Reseller this unit is warranted by the seller to the purchaser against defects in workmanship and the materials used in its manufacture for a period of one year from the date of sale Faults arising from misuse unauthorised modifications or accidents are not covered under this warranty No other warranty is expressed or implied If the unit is faulty it should be sent to the seller of the equipment in its original packaging with shipping prepaid The unit will be returned to you when the repair has been completed If the unit was purchased in the European Union you may as an alternative return the unit to any other BSS distributor in
13. 30dB of range is available before noticeable distortion occurs Another piece of information also displayed by these meters is the amount of gain reduction still available from the VCAs window of operation If you consider that the input signal is of such a level that 15dB of gain reduction is occurring i e the 15dB LED on the gain reduction meter is on then the length of GAIN REDUCTION meter display remaining unlit is an accurate visual indication of how much headroom still exists within the circuitry O bserving this information will ensure that the output signal is unlikely to incur distortion as a consequence of overloading the VCA A further operational feature of this meter is its ability to intensify brightness when the VCA window isin danger of being exceeded and distortion is likely to occur Input signals causing an excess of 30dB of gain reduction will initiate the bright up and the display will appear to flash to alert attention This feature is especially Page 15 BSS Audio D PR 402 User Manual v3 0 useful when a rack of equipment contains a number of DPR 402 units the ability to immediately pick out the particular channel that is in danger of distortion will be much appreciated 11 2 Output Level Meter and Meter Input Switch This meter monitors the signal level at the output of the DPR 402 and gives an absolute reading of its level This meter also incorporates the bright up feature which will occur when the ou
14. 500 milliseconds slow setting Harmonic distortion will increase with reduced frequency and shorter time constants which is inherent in this type of equipment Attack times are those as measured to achieve 63 of final gain reduction with a step signal of 8dB above threshold Release times are those as measured to achieve 63 recovery of open gain or removal of a signal of 8dB above threshold The frequency is that at which 3dB of gain reduction occurs for 10dB of signal overdrive above threshold 10dB of gain reduction will occur at and above twice this frequency 3 position switch to select Normal mode to allow simultaneous wide band de essing compressing and peak limiting Wide band de ess mode utilising compressor side chain HF de ess mode utilising compressor side chain Page 31 BSS Audio Metering Stereo Switch Rear Panel Rear Connections Power Mounting requirements Weight D PR 402 User Manual v3 0 Bypasses all functions of the unit at unity gain allowing all parameters to be adjusted and levels checked whilst on air Momentarily connects the control side chain to the output of the unit to allow monitoring of control insert return Momentarily connects the input signal to the output level meter to allow comparison of input and output levels prior to operating the bypass switch BELOW THRESHOLD 5 LEDs to indicate side chain level from 18dB to OGB ref the set threshold
15. BSS Audio D PR 402 User Manual v3 0 V 3 0 JMK 27th October 1997 DPR 402 User Manual This equipment has been tested and found to comply with the following European and international Standards for Electromagnetic Compatibility and Electrical Safety Radiated Emissions EU EN 55013 1990 Associated Equipment RF Immunity EU EN 50082 1 1992 RF Immunity Fast Transients ESD Mains Disturbance EU EN 61000 3 2 1995 Electrical Safety EU EN 60065 1993 Radiated Emissions U SA FCC part 15 Class B Electrical Safety U SA UL813 ETL 1996 Commercial Audio Equipment Electrical Safety CAN UL813 ETLc 1996 Commercial Audio Equipment IMPORTANT SAFETY INFORMATION DO NOT REMOVE COVERS NO USER SERVICEABLE PARTS INSIDE REFER SERVICING TO QUALIFIED SERVICE PERSONNEL THIS EQUIPMENT MUST BE EARTHED IT SHOULD NOT BE NECESSARY TO REMOVE ANY PROTECTIVE EARTH OR SIGNAL CABLE SHIELD CONNECTIONS TO PREVENT GROUND LOOPS ANY SUCH DISCONNECTIONS ARE OUTSIDE THE RECOMMENDED PRACTISE OF BSS AUDIO AND WILL RENDER ANY EMC OR SAFETY CERTIFICATION VOID For continued compliance with international EMC legislation ensure that all input and output cables are wired with the cable screen connected to Pin 1 of the XLR connectors The input XLR Pin 1 is connected to the chassis via a low value capacitor providing high immunity from ground loops whilst ensuring good EMC performance We have written this manual with the aim of helping instal
16. LINK NORMAL COMPRESSION D G C B eee al H F RE EMPHASISED COMPRESSION Compression is higher at LOW frequencies This arrangement will make heavily compressed signals sound brighter as it lessens the effect of heavy low frequencies modulating the treble H F RE EMPHASISED COMPRESSION F G F B As above but more pronounced L F RE EMPHASISED COMPRESSION D G E B Compression is higher at HIGH frequencies This is useful for controlling harsh or shrill components of a signal allowing faster ATTACK and DECAY to be used before LF distortion becomes a problem L F RE EMPHASISED COMPRESSION E G E B Compression is higher at HIGH frequencies This is useful for controlling harsh or shrill components of a signal allowing faster ATTACK and DECAY to be used before LF distortion becomes a problem Page 25 BSS Audio D PR 402 User Manual v3 0 SUBTRACT CONTROL S C LINK S C LINK WIDE BAND L F CONTROL COMPRESSION D G This mode compress the entire audio spectrum under control of the frequencies below that set by the FREQ control The modulation of H F signals by the L F signals is an effect which may be desired NARROW L F CONTROL COMPRESSION Only frequencies below that set on the FREQ control are compressed Low frequencies are compressed without modulating the high frequencies which pass unattenuated The PEAK LIMITER and DE ESSER should not normally be used in this mode EXPANDER WIDE BAND When input signals excee
17. To aid the correct setting of the FREQ control in relation to the audible sibilance the source program can be listened to through the internal de ess filter by depressing the MON S C switch This replaces the normal signal at the output connector with the output of the de ess filter 12 4 Peak Limiting Referring back to section 3 De essing and Peak Limiting the problems with high frequency transients causing distortion further down the equipment line were discussed The peak limiter of the DPR 402 provides an extra stage of gain reduction with dynamics specifically set for these fast transients It is used in conjunction with the main compressor section and provides an output limiting function to control the fast transients which would generally be missed by the slower dynamic settings of the compressor The attack and release times are set internally to suit the limiting application with a choice of FAST or SLOW response selected by a switch on the rear panel refer to section 9 Input and O utput Connections Rear Panel Facilities It is preferable to use the FAST response setting providing this does not cause audible distortion otherwise the SLOW response should be used The peak limiter threshold is unaffected by the GAIN control and is set by the PEAK LIM control which is scaled directly in dBv The ratio is set internally to 20 1 A green LED is provided to indicate when limiting begins and a red LED indicates when heavy limiting o
18. and is one part of the DPR 402 Page 4 BSS Audio D PR 402 User Manual v3 0 1 2 Compressors and Limiters Compressors and limiters have closely related effects and in general a limiter will reduce gain very strongly once a certain level has been reached whereas a compressor will act gently but over a much wider range of volume levels A limiter will continuously monitor program levels but only commence to reduce gain once the level has exceeded a preset amount This point is called the threshold level Any program level in excess of the threshold will immediately be reduced to this threshold level A compressor will also continuously monitor the program and has a threshold level However program signals in excess of this threshold will be progressively reduced by an amount ratio depending on the degree to which it initially exceeds the threshold Generally threshold levels for compressors are set below the normal operating level to allow them to reduce the dynamic range of the signal gradually so that they are acceptable to following equipment For limiters the threshold point will be set above the operating level in order to provide a maximum level for signals to following equipment 2 The effect of Compression on sound 2 1 Compression Consider an input signal which is applied to two units one having its threshold point set 10dB higher than the other See figures 2 1 a b Since the compressor only affects signals that exceed
19. been if no action had been taken This action is known as the ratio A ratio of 1 1 indicates that the output will linearly track the input level of the threshold i e For every 1dB of input over the threshold point there will be 1dB of output A ratio of 2 1 indicates that for every 2dB of input level above the threshold there will be a corresponding increase of 1dB in the output level A ratio of 10 1 indicates that for every increase of 10dB of input level there will be a corresponding increase of 1dB in the output level and so on A ratio of infinity 1 indicates that no matter how loud the input signal goes above the threshold the output will remain constant at the threshold point It is worth noting that a hard or infinite ratio limit has applications in some specialised situations but in general it is neither appropriate nor necessary and is likely to cause noticeable side effects in the sound 3 De essing and Peak Limiting A common problem encountered when amplifying the human voice is the large amount of High Frequency energy heard as the sibilant sss sound These high frequency or sibilant sounds can reach levels considerably greater than the normal voice level and will result in signal break up or distortion It is possible to control these sounds independently of the normal program by making the normal compressor sensitive only to these high frequencies Selective high frequency compression is generally called de essing as it rem
20. ccurs above 10dB This red LED indicates that more than optimum peak limiting is being used and the output gain control should therefore be backed off so that it only flashes on occasional peaks Page 18 BSS Audio D PR 402 User Manual v3 0 13 Rear Barrier Strip The DPR 402s rear barrier strip provides an interface with the main compressor section allowing for various configurations which utilise the internal facilities as well as external equipment For correct operation of the unit make sure that both the SUBTRACT and CONTROL side chain points are closed either by links or by externally connected equipment Connections to the subtract side chain will be phase conscious whereas those to the control will not be Any externally connected equipment should operate at unity gain and be capable of handling signal levels up to 20dBv Rear Barrier Strip Designations Pin Function A Ground B Insert Return Control Side Chain C Insert Send Reversed Phase D Insert Send Normal Phase E Insert Send L F Re emphasised F Insert Send H F Re emphasised G Insert Return Subtract Side Chain H Insert Return Subtract Side Chain Gain Link Expand or over infinity mode J Ground K Insert Send Subtract LP Filter L Insert Send Control LP Filter M Stereo Link Page 19 BSS Audio D PR 402 User Manual v3 0 14 Operation and Applications 14 1 Compression Barrier strip linking B C and D G as factory set Initial settings
21. control with the main signal but this time under control of the same or another external control input These two modes may be used to good effect when the external signal is an echo return or delayed signal For example a single voice can be automatically chorused above the set threshold 15 3 Stereo Linking W hen stereo signals are compressed it is necessary for the gain of both channels of the compressor to be identical at any moment in time otherwise the stereo image will move around the sound picture as the relative levels of the left and right hand signals vary Stereo linking couples together the compressor control signals so that the VCAs in both channels work together as in a stereo fader It should be noted however that when in stereo linked mode the standard DE ESS and PEAK LIMITER functions continue to operate independently for each channel and are not part of the stereo linking There are three possible ways to stereo link of the DPR 402 Stereo Link Switch When the rear panel STEREO LINK switch in ON both channels are couples together and the LINK LED illuminates on the front panel In this mode it is important that the compressor controls are set identically for both channels Hard Wired Stereo and Multiple Channel Linking The stereo coupling point is available at connection M on the BARRIER STRIP and up to four channels may be coupled together by simply strapping these pins together Screened cable
22. d the set threshold expansion occurs since the subtract side chain signal is added to the main signal The DE ESSER should not normally be used in this mode The PEAK LIMITER may be used for effect EXPAN DER L F ONLY As above but only those frequencies below that set by the FREQ control are expanded EXPANDER L F CONTROL MODE switch to COMPRESS EXPANDER H F CONTROL MODE switch to DE ESS WIDE Q T B Pa P o W Ww w Ww As in wide band expansion occurs over the entire audio bandwidth However it is under the control of either low or high frequencies as set by the links and FREQ control EXTERNAL GAIN CONTROL By driving the control s c with an external signal the amplitude of the main signal will be modulated by the envelope of the external control signal By choosing links on the subtract s c modulation can be wide band or L F only DE ESS and PEAK LIMITER should not be used in this mode EXT SIG OU a O Page 26 BSS Audio D PR 402 User Manual v3 0 SUBTRACT CONTROL S C LINK S C LINK AMPLITUDE CONTROLLED MIXING 1 EXT oe to C B In this mode an external signal will be summed with K B the main signal and appear on the compressor under control of the amplitude of the main signal Wide band link C B L F only link K B H F only link C B and MODE switch to DE ESS WIDE AMPLITUDE CONTROLLED MIXING 2 a SIG to EXT SIG to B As above but the external signal will be summed sum
23. e output uncompressed How the compressor performs on the signal once inside the window is controlled by the RATIO ATTACK and RELEASE controls 10 2 Ratio The effect of the ratio control can be shown on a graph which plots input level and clearly shows that below threshold the DPR 402 acts purely as a linear amplifier In applications where gentle compression is required it is advantageous to change from the linear to compression region in a very gradual manner rather than the more conventional abrupt manner as shown in the diagram The DPR 402 has been configured so that for low settings of the ratio control and low levels of compression the transfer is soft and for increasing ratio settings and high levels of compression the transfer becomes harder This progressive knee gives inaudible compression for low levels of ratio and gain reduction whilst allowing harder compression for extreme control when required Page 12 BSS Audio D PR 402 User Manual v3 0 10 3 Attack Time The response of the DPR 402 compressor to signals above the threshold point is further defined by the ATTACK TIME control The DPR 402 ATTACK TIME control has 11 calibrated positions from 50 microseconds to 100 milliseconds and determines how quickly the compressor responds to signals once the threshold is exceeded As explained earlier for fast transients a fast attack time is desirable For other types of program material a slower time will be mo
24. e unit please inspect for any physical damage and retain the shipping carton and ALL relevant packing materials for use should the unit need returning In the event that damage has occurred please notify your dealer immediately so that a written claim to cover the damages can be initiated Page 9 BSS Audio D PR 402 User Manual v3 0 7 Mechanical Installation A vertical rack space of 1U 13 4 102mm deep is required Ventilation gaps are unnecessary If the DPR 402 is likely to undergo extreme vibration through extensive road trucking and touring it is advisable to support the unit at the rear and or sides to lessen the stress on the front mounting flange The necessary support can generally be bought ready built as a rack tray As with any low level signal processing electronics it is best to avoid mounting the unit next to a strong source of magnetic radiation for example a high power amplifier to help keep residual noise levels in the system to a minimum 8 Mains Power Connection Voltage The DPR 402 operates on either 120 or 240 volt supplies Use the voltage selector switch to choose the required voltage setting Frequency Both 60Hz and 50Hz are acceptable Grounding The DPR 402 must always be connected to a 3 wire grounded earthed AC outlet The rack framework is assumed to be connected to the same grounding circuit The unit must NOT be operated unless the power cables ground earth wire is properly
25. es Page 21 BSS Audio D PR 402 User Manual v3 0 14 4 De ess Wide with Full Dynamic Control Barrier strip linking B C and D G as factory set Initial settings Controls Position MODE SWITCH De ess wide THRESHOLD Out RATIO Infinity ATTACK 50 microseconds RELEASE 100 milliseconds GAIN OdB CHN BYPASS In Illuminated DE ESSTHRSHLD Out FREQ AkHz PK LIM THRSHLD Out Rotate the THRESHOLD control anticlockwise until the BELOW THRESHOLD meter is fully illuminated and an appropriate amount of gain reduction is indicated on the GAIN REDUCTION meter The FREQ control and THRESHOLD control can now be fine tuned to achieve the desired effect whilst listening to the program Gain compensation will not normally be required when de essing Although fast attack and release times are most appropriate they should be adjusted to achieve the best results The auto position should NOT be used To aid the correct setting of the FREQ control in relation to the audible sibilance the source program can be listened to through the internal de ess filter by depressing the MON S C switch This replaces the normal signal at the output connector with the output of the de ess filter The peak limiter can be used simultaneously with wide band de essing should it be required Page 22 BSS Audio D PR 402 User Manual v3 0 14 5 De ess HF with Full Dynamic Control Barrier strip linking B C and D G as factory set Initial settings Controls Po
26. g Rotating the threshold control anticlockwise effectively lowers the window of the VCA allowing it to sit at the right point on the input signal O bservation of this meter during program will give an instant picture of how much of the input signal is being processed or how near the peaks are to being processed This will provide valuable information at all times during use especially for live concert work where signal levels tend to increase during the course of the show Once the input signal has exceeded the threshold point on scale the compressor starts to operate and gain reduction will occur The amount of gain reduction being used is displayed on the GAIN REDUCTION meter Gain reduction is a useful way of expressing compressor action We have seen that the output level of a compressor is less than the input level by some amount that depends on the threshold ratio attack and release time settings If for example a particular signal transient exceeds the threshold point by 10dB and the ratio knob is set to 2 1 then we would expect the output to have only increased by 5dB providing the time controls are set accordingly Assuming the gain control is at OdB the difference between the input and output levels of 5dB then represent the amount of gain reduction which has occurred and will be displayed on the gain reduction meter as 5dB The range of the gain reduction meter is set to display the 27dB operating window In practice over
27. gt 10k and a low output impedance gt 1k In order to preserve the THRESHOLD control calibration it is essential that unwanted frequencies are attenuated rather than wanted frequencies boosted by the external filter For example if compression is to be controlled by a narrow mid band of frequencies then the low frequency and high frequency sliders should be pulled down and the mid band sliders left at OdB Page 24 BSS Audio D PR 402 User Manual v3 0 Subtracting Side Chain Inserting an external equaliser into the subtract side chain has the effect of modifying the tonal balance of the processed signal by adding or subtracting a specific band of frequencies The external equipment should meet all the requirements specified in the control side chain section above and be operated in a similar manner The adding or subtracting process requires that all signals are appropriately phased and the gain be unity Any errors may lead to unexpected results For the units DE ESS HF function the internal filters have been phase and amplitude corrected to achieve the required response 15 2 Repatching of the Barrier Strip for other uses and Special Effects The following table lists many of the possible uses of the DPR 402 This is not an exhaustive list and other combinations may be tried To obtain the full benefits of its versatility a simple understanding of how it works is required refer to section 13 Rear Barrier aE S C LINK S C
28. hold THD lt 0 03 20Hz 20kHz Typically 0 002 at 1kHz IMD lt 0 01 SMPTE Typically 0 003 10dB compression Threshold OdB 1kHz 5sec rel Time see note 1 2nd Harmonic lt 0 15 3rd Harmonic lt 0 05 IMD SMPTE lt 0 25 Better than 85dB 20Hz to 20kHz any settings 30dBv to 20dBv continuously variable 1 1 to infinity 1 continuously variable O ver infinity available by Barrier strip re linking gt 30dB 50 microseconds to 80 milliseconds in 11 switched steps see note 2 5 milliseconds to 5 seconds in 10 switched steps and AUTO see note 2 A two part program dependant time constant Attack time is typically 200 microseconds on fast transient overdrives Release is typically 10 milliseconds for Page 30 BSS Audio 17 3 De esser Threshold Range Ratio Frequency Range 17 4 Peak limiter Threshold Range Ratio Attack Time Release Time 17 5 Notes Note 1 Note 2 Note 3 17 6 Facilities Mode Switch Bypass Switch MON S C Switch Meter Input Switch D PR 402 User Manual v3 0 63 recovery from a 10dB 4 millisecond overdrive and 1 second for a 10dB 40 millisecond overdrive 30dBv to 20dBv continually variable Infinite at and above twice the set frequency 700Hz to 20kHz continuously variable see note 3 4dBv to 20dBv continuously variable gt 20 1 150 microseconds fast setting 750 microseconds slow setting 100 milliseconds fast setting
29. in compressor section If it is used exclusively on its own then dynamic distortions will generally result on program signals having anything other than high frequency content 4 The BSS DPR 402 The BSS DPR 402 compressor de esser and peak limiter has been designed in response to the demand for a versatile compact stereo unit which provides the three most commonly used dynamic functions in a single 1 unit rack space The internal architecture including two independent insert accessible side chains per channel allows unprecedented flexibility and scope for the creative operator In its normal mode however this complexity remains totally invisible for the user who required a conventional system with operational simplicity The dedicated de esser control and associated variable filter allow wide band sibilance control simultaneously with compression and peak limiting For highly critical de essing application the compressor section can be switched to operate at high frequencies only i e as a dynamically controlled tunable HF filter The compressor section allows you full control over all the normal parameters and offers auto time constants for general purpose use The control and subtract side chain insertion points allow numerous applications for the patching of the units own or external filters to provide dynamic tonal modification The calibrated peak limiter allows absolute control without having to compromise the dynamics setting
30. lers and sound engineers to get to grips with the DPR 402 and obtain its maximum capability If you are new to BSS products we recommend that you begin at the start of the manual We welcome any comments or questions regarding the DPR 402 or other BSS products and you may contact us at the address or World Wide Web site given in the warranty section Page 1 BSS Audio D PR 402 User Manual v3 0 Contents 1 Compressors and Limiters 1 1 The need for Gain Control 1 2 Compressors and Limiters 2 The effect of Compression on sound 2 1 Compression 2 2 Attack Release and Ratio 3 De essing and Peak Limiting 4 The BSS DPR 402 5 Earthing Requirements 6 Unpacking 7 Mechanical Installation 8 Mains Power Connection 9 Input and Output Connections Rear Panel Facilities 9 1 Inputs 9 2 Outputs 9 3 Stereo Link 9 4 Barrier Strip 9 5 Peak Limiter Switch 10 Compression Controls 10 1 Threshold 10 2 Ratio 10 3 Attack Time 10 4 Release time 10 5 AUTO TIME 10 6 GAIN control 10 7 BYPASS switch 10 8 MODE switch 11 Compression meters 11 1 Below Threshold and Gain Reduction Meter 11 2 Output Level Meter and Meter Input Switch 11 3 MON S C switch 12 De essing and Peak Limiting 12 1 De essing 12 2 Broadband De essing and controls 12 3 HF Only De essing and Controls 12 4 Peak Limiting O ON oT opr BSS Audio D PR 402 User Manual v3 0 13 Rear Barrier Strip 19 14 Operation and Applications 20 14 1 Compression 20 14 2 De essing 20
31. llow Earth Blue N eutral Brown Live As the colours of the wires in the mains lead may not correspond with the markings identifying the terminals in your plug proceed as follows e The wire which is coloured Green and Yellow or Green must be connected to the terminal which is marked with the letter E or by the Earth signal or which is coloured Green and Yellow or Green e The wire which is coloured Blue must be connected to the terminal labelled N or coloured Black or Blue e The wire which is coloured Brown must be connected to the terminal labelled L or coloured Red or Brown Those units supplied to the North American market will have an integral moulded 3 pin connector which is provided to satisfy required local standards The mains voltage selector switch provides a simple external adjustment to allow operation on all international AC power standards The allowable ranges for the supply voltage are 90VAC up to 132VAC on the 115V position and 190VAC up to 264VAC on the 230V position Outside these ranges the unit will not work satisfactorily if at all Voltages in excess of the maximum will probably cause damage Voltages below the minimum will cause the power supplies to drop out of regulation degrading the performance of the system 6 Unpacking As part of BSS system of quality control this product is carefully inspected before packing to ensure flawless appearance After unpacking th
32. mpression Controls 10 1 Threshold In the DPR 402 the gain reduction is achieved using a Voltage Controlled Attenuator with a range or operational window of 30dB This means that it is capable of reducing the input signal by up to 30dB or 30 times the GAIN REDUCTION METER displays this window showing how much of it is being used The voltage level corresponding to the lower boundary of this window is called the threshold and input signals below this level cannot cause gain reduction When the input level enters the window by exceeding the threshold gain reduction can occur the amount of gain reduction or compression produced being directly proportional to the amount by which input signal level exceeds the threshold The upper boundary of the VCA window is set by the circuitry at a level 30dB above the threshold The THRESHOLD control adjusts the threshold relative to the input signal in order to set the compressor to the required amount of gain reduction For example if the average input is 12dBv and the THRESHOLD control is set to 10dBv then the top 22dB 12 10 22dB of the signal can be compressed The THRESHOLD control is adjustable from 30dBv to over 20dBv It should be noted that when the THRESHOLD control is set fully clockwise to the position marked OUT this corresponds to a threshold level above 20dBv so that no matter how high the input level stage will clip before the threshold is reached the signal will reach th
33. need for more comprehensive control of the de essing function arise then the main compressor section can be configured to operate as a dedicated de esser by operating the mode switch The amount of gain reduction can then be extended down to 30dB if required and this gives full control over the dynamic settings as in normal compression Page 17 BSS Audio D PR 402 User Manual v3 0 12 3 HF Only De essing and Controls To achieve this mode of operation the main compressor must be utilised as an exclusive de esser by operation of the MODE switch to DE ESS HF Gain reduction at high frequencies only is achieved by inserting an internal high pass filter into the subtract side chain so that only these high frequencies are available to the subtractor The front panel FREQ control adjusts both this filter and the control side chain filter simultaneously to provide a de essing range from 700Hz to 20kHz HF only de essing is achieved by operating the compressor controls as for normal compression refer to section 10 Compression Controls and utilising the FREQ control to allow only the sibilant frequencies to cause gain reduction If general compression is required simultaneously then channel 2 of the unit can be used by connecting the two channels in series It should be remembered that in this mode the DE ESS and PEAK LIM controls must be set to OUT as they cannot be used simultaneously with the compressor switched to dedicated de ess mode
34. of the compressor potentially resulting in less dynamic distortion for an equivalent amount of compression The DPR 402s user friendliness is well demonstrated by the sophisticated yet uncluttered LED metering and monitoring facilities The full compressor operating range is displayed on a two part meter indicating both signals below threshold and actual gain reduction The arrangement of these two meters together with the full scale bright up feature ensures that operation will always be within the permitted VCA window making it virtually impossible to exceed the systems parameters unintentionally The output is continuously monitored on the output level meter which also incorporates the full scale bright up facility The bypass switch in conjunction with the meter input switch provides a powerful aid for initially setting up the unit The straight signal and the processed signal may be monitored on the output level meter without affecting the output from the unit thus enabling system gains to be equalised while in the bypass mode Like all BSS Audio equipment the DPR 402 has been designed to withstand harsh treatment on the road yet has a specification to satisfy the most stringent studio and broadcast work Page 8 BSS Audio D PR 402 User Manual v3 0 5 Earthing Requirements WARNING THIS APPLIANCE MUST BE EARTHED IMPORTANT The wires in the mains lead are colour coded in accordance with the following code Green and Ye
35. or rack mounted unbalanced audio systems the case power ground can be isolated from the signal by removing an internal wire link associated with channel one output 9 3 Stereo Link This facility enables the two channels of the DPR 402 to be used in a stereo system with the result that there is no image shifting under comparison on either channel This switch actually couples the detector outputs from both channels together so that either one responds to the largest signal present When in stereo mode the front panel LIN K LED will illuminate and care should be taken to ensure that both channels have their controls set equally For other methods of multiple channel coupling refer to section 14 O peration and Applications 9 4 Barrier Strip This interface facility provides various input and output signals to the unit allowing other dynamic controlling features to be realised This strip also includes the two insertion points for external equipment connections and in the absence of these the two indicated shorting links must be made to allow normal operation of the unit Please refer to section 14 O peration and Applications for examples of possible uses 9 5 Peak Limiter Switch This fast slow selector changes the dynamic response of the peak limiter section to best suit the particular program material Please refer to section 12 4 Peak Limiting for applications and usage Page 11 BSS Audio D PR 402 User Manual v3 0 10 Co
36. oves the sss content from the program Referring to section 2 2 Attack Release and Ratio attack time was defined as the time taken for the compressor to respond to program levels which have exceeded its threshold level It is also found that for relatively low frequencies a longer attack time is required than for high frequencies to avoid any unpleasant dynamic distortions When compressing a program mix that includes a wide range of frequencies some compromise must be made to the setting of the attack time and this will inevitably result in a setting that suits the lowest frequency components present For general dynamic range controlling using a compression mode this is of no serious consequence However in a limiting mode where the peaks of the signal are being restricted to a maximum operating level to avoid distortions in following equipment it is essential to have the attack times as fast as possible for all frequency components O perating the compressor in a limiting mode with a high ratio high threshold and dynamic settings to suit the low frequency components will result in very fast high frequency signal transients passing through without causing gain reduction These transients can then cause distortions in following equipment such as tape recorders and radio transmitters Page 7 BSS Audio D PR 402 User Manual v3 0 It should be remembered that the DPR 402 is a peak limiter designed to be used in conjunction with the ma
37. pecified dynamic range whereas for limiting purposes where transient peaks are to be kept clear of the headroom limits a faster attack and release time is required The range provided by the DPR 402 on its time controls is sufficient to allow its use either as a compressor or limiter and the AUTO facility is scaled primarily for compression use 2 2 Attack Release and Ratio Attack is the amount of time that elapses before the compressor begins to attenuate the output level after the threshold point has been exceeded For sounds such as a snare drum or hand clap fast attack is desirable so that the compressor responds in time to control the peaks Release is the amount of time taken for the compressor to return to normal gain after the input signal has fallen BELOW the threshold point Ratio determines the ratio of change on output level to changes in input level for all signals that exceed the threshold Returning to section 1 1 The need for Gain Control where the idea of manual controlling the level of the program was Page 6 BSS Audio D PR 402 User Manual v3 0 discussed the operator would reach over and turn down the volume if signal levels were approaching distortion At this point he now has an option Either reduce the level so that there is nothing exceeding his desired maximum level or reduce the level by a small amount so that his output is slightly greater than that of his preferred maximum but not as loud as it would have
38. re useful It is always preferable to start with a slower time and progressively speed up the response as necessary since too fast a time may cause distortion of the sound 10 4 Release time Another parameter which affects the compressor performance is the RELEASE TIME control The release time control has 10 calibrated positions from 5 milliseconds to 5 seconds and determines how quickly the compressor returns to normal gain following a transient in excess of the threshold The setting of the release time is very much dependant on program type and the setting of a wrong speed will result in either of two conditions If set too fast the overall volume level will jump up and down exactly following the peaks above threshold and this will produce an objectional and unsettling effect If set too slow quiet parts of the program immediately following loud transients will be subjected to breathing or pumping effects caused by the VCA releasing its attenuation or effectively the system gain during the quiet program period when it is not required 10 5 AUTO TIME This feature of the DPR 402 is provided to overcome some of the settling problems associated with the attack and release time control features It is accessed by switching the released time control to the AUTO position whereupon the circuit automatically adjusts itself to provide the required attack and release time settings depending on the program type The circuitry
39. sition MODE SWITCH De ess wide THRESHOLD Out RATIO Infinity ATTACK 50 microseconds RELEASE 100 milliseconds GAIN OdB CHN BYPASS In Illuminated DE ESSTHRSHLD Out FREQ AkHz PK LIM THRSHLD Out Rotate the THRESHOLD control anticlockwise until the BELOW THRESHOLD meter is fully illuminated and an appropriate amount of gain reduction is indicated on the GAIN REDUCTION meter The FREQ control and THRESHOLD control can now be fine tuned to achieve the desired effect whilst listening to the program Gain compensation will not normally be required when de essing Although fast attack and release times are most appropriate they should be adjusted to achieve the best results The auto position should NOT be used To aid the correct setting of the FREQ control in relation to the audible sibilance the source program can be listened to through the internal de ess filter by depressing the MON S C switch This replaces the normal signal at the output connector with the output of the de ess filter The peak limiter should NOT be used in the HF mode Page 23 BSS Audio D PR 402 User Manual v3 0 14 6 Peak Limiting The peak limiter is designed to be used in conjunction with compression and or any wide band de essing It should not be used simultaneously with HF de essing or when external filters are patched into the SUBTRACT side chain Terminal G Barrier strip linking D G other links to suit functions as required Initial settings
40. t whatsoever on the signal except at the moment of sibilance and then the effect is only of overall level change There is no change in the general frequency response yet sibilance is controlled 12 2 Broadband De essing and controls Broadband de essing can be achieved either simultaneously with normal compression on the same channel of the DPR 402 utilising DE ESS and FREQ controls or exclusively on the one channel by setting the MODE switch to DE ESS WIDE and utilising the compressor section controls In utilising the controls no other compressor controls will be required If no compression is being used the ratio or threshold controls should be set to OUT The frequency control should be set to coincide with the lowest frequency of the sibilance and the de ess control be used to give the required amount of gain reduction The maximum amount of reduction available in this mode is 20dB The dynamic settings for this compression are set automatically by the unit and are optimised for general vocal work The green and orange LEDs above the de ess control provide a simple indication of the degree of de essing with the green LED indicating the start of the operation and the orange LED indicating approximately 15dB of gain reduction Having only a frequency and level control for this broadband de essing function provides a very simple and effective way of treating general sibilant vocal signals when processed on their own Should the
41. tput signal level reaches 20dBv The METER INPUT switch is used in conjunction with the OUTPUT LEVEL meter to allow the input signal to be displayed The switch has a momentary action to ensure that the meter is not inadvertently left showing input level This facility becomes extremely useful when used in conjunction with the BYPASS switch During initial setting up of routines and prior to going on air the signal output level will be different from the input Utilising this meter input switch will enable the input and output levels to be compared on the same display and adjustments can then be made accordingly with the GAIN control to ensure that the input and output levels are similar the GAIN control will only affect the output signal level Once satisfied of this condition operation of the BYPASS switch will ensure an unnoticeable drop in 11 3 MON S C switch This switch will change the output connector of the DPR 402 from the normal compressor output and connect it to the return of the control side chain insertion point This will allow monitoring of any external equipment which is connected to the unit to assist in its setting up For applications and a description of side chain insertions please refer to sections 13 Rear Barrier Strip and 14 O peration and Applications 12 De essing and Peak Limiting 12 1 De essing In section 3 De essing and Peak Limiting the problems with high frequency energy also known as
42. with full dynamic control and de ess H F Page 20 BSS Audio D PR 402 User Manual v3 0 with full dynamic control De ess wide attenuates with whole frequency spectrum and although acceptable for most vocal sources it may cause undesirable side effects on a mixed program source refer to section 12 2 Broadband De essing and controls and 12 3 HF Only De essing and Controls D e ess HF only attenuates the high frequencies and therefore produces superior results in all cases which is essential when de essing a mixed program source If simultaneous de ess HF and compression are required the separate channels must be used for each function 14 3 De essing Wide with Simultaneous Compression Barrier strip linking B C and D G as factory set Initial settings Set all compressor controls as required refer to section 14 1 Compression For optimum de essing effect no more than 10 15dB of compression should be used If compression is not required then set THRESHOLD to OUT Controls Position DE ESSTHRSHLD OUT FREQ 4kHz PK LIM THRSHLD OUT Under program control gradually rotate the DE ESS THRESHOLD control anticlockwise until the required effect is achieved The FREQ control can also be adjusted to ensure that frequencies lower than those causing concern do not initiate de essing It should be remembered that this de essing is wideband and may cause distortion or pumping effects if the source program contains significant low frequenci
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