DPR 402 User Manual 1
V3.0 JMK 13 May 1997 This equipment has been tested and found to comply with the following European Standards for Electromagnetic Compatibility: Emission Specification: EN55013 (1990) (Associated equipment) Immunity Specification: EN50082/1 (1992) (RF Immunity, Fast Transients and ESD) Mains Disturbance: EN61000/3/2 (1995) For continued compliance ensure that all input and output cables are wired with cable screen connected to Pin 1 of the XLR.
Contents Contents 1.0 Compressors and Limiters 5 The need for Gain Control Compressors and Limiters 5 6 The effect of Compression on sound 7 Compression Attack, Release and Ratio 7 8 3.0 De-essing and Peak Limiting 9 4.0 The BSS DPR-402 9 5.0 Earthing Requirements 10 6.0 Unpacking 11 7.0 Mechanical Installation 14 8.0 Mains Power Connection 15 9.0 Input and Output Connections Rear Panel Facilities. 16 1.1 1.2 2.0 2.1 2.2 9.1 9.2 9.3 9.4 9.5 10.0 10.1 10.2 10.3 10.4 10.5 10.
Contents 12.0 12.1 12.2 12.3 12.4 De-essing and Peak Limiting 25 De-essing Broadband De-essing and controls HF Only De-essing and Controls Peak Limiting 25 25 26 27 13.0 Rear Barrier Strip 28 14.0 Operation and Applications 29 14.1 14.2 14.4 14.3 14.5 14.6 15.0 15.1 15.2 15.
Compressors and Limiters 1.0 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.
Compressors and Limiters Fig 1.2 Operating level and Headroom 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.
The effect of Compression 2.0 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. Since the compressor only affects signals that exceed the threshold level, the signal with the lower threshold applied will be more affected than the other. Referring to figures Fig 2.1a High threshold level Fig 2.1b Lower threshold level 2.
The effect of Compression Comparing the input and output waveforms for the compressed mode, the loudest portions of the signal have been effectively decreased in level, and if the gain control is adjusted to compensate for this, the quieter portions will be increased. The net effect, therefore, is for both ends of the dynamic spectrum to be pushed (or squeezed) towards each other.
De-essing and Peak Limiter The DPR-402 3.0 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.
Earthing Requirements 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.
Unpacking 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.
Getting to know the DPR-402 Fig 6.1 Front Panel Fig 6.
All numbers in bubbles refer to Section numbers.
Mechanical Installation 7.0 Mechanical Installation A vertical rack space of 1U (1¾" / 10½mm) deep is required. Ventilation gaps are unnecessary (See Figure 7.1). 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.
Mains Power Connection 8.0 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. (See Figure 8.1). Frequency: Both 60Hz and 50Hz are acceptable. Fig 8.1 Mains fuse on rear panel. 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.
Inputs/Outputs 9.0 Input and Output Connections Rear Panel Facilities. 9.1 Inputs The input (See figure 9.1) 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.
9.3 Stereo Link This facility (See figure 9.4) 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 'LINK' LED will illuminate, and care should be taken to ensure that both channels have their controls set equally.
Compression Controls 10.0 Compression 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).
Fig 10.3 The effect of Ratio on the Output Signal 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 (See figure 10.4). 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.
Compression Controls 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 (See figure 10.6).
10.7 BYPASS switch The BYPASS switch (See figure 10.8) 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 light is 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.
Compression Meters 11.0 Compression meters 11.1 Below Threshold and Gain Reduction Meter Referring back to section 10.1, where we discussed the VCA window of operation, the five LEDs (See figure 11.1) 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.
Fig 11.3 Compression expressed as Gain Reduction The range of the gain reduction meter is set to display the 27dB operating window. In practice, over 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.
Compression Meters 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 (See figure 11.5). Fig 11.5 METER INPUT switch 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.
De-essing and Peak Limiting 12.0 De-essing and Peak Limiting 12.1 De-essing In section 3 the problems with high frequency energy, also known as 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.
De-essing and Peak Limiting Fig 12.1b DE-ESS Controls In utilising the controls in figure 12.1b, 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.
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 effect of de-essing at various frequencies on a program is shown in figure 12.3. Fig 12.3 Effect of de-essing on output 12.
Rear Barrier Strip 13.0 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.
Operation/Applications 14.0 Operation and Applications 14.1 Compression Barrier strip linking B-C and D-G (as factory set). Initial settings. Controls Position MODE SWITCH Compress THRESHOLD Out RATIO 4 ATTACK - RELEASE Auto GAIN 0dB CHN BYPASS In (Illuminated) DE-ESS THRSHLD 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.
Operation/Applications 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). For optimum deessing effect, no more than 10-15dB of compression should be used. If compression is not required, then set THRESHOLD to OUT.
14.5 De-ess HF with Full Dynamic Control Barrier strip linking B-C and D-G (as factory set). Initial settings.
Barrier Strip Applications 15.0 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.
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). MODE SUBTRACT S/C LINK NORMAL COMPRESSION CONTROL S/C LINK D-G C-B D-G F-B F-G F-B D-G E-B E-G E-B D-G L-B Compression occurs equally at all frequencies. H.F.
Barrier Strip Application MODE NARROW L.F. CONTROL COMPRESSION SUBTRACT S/C LINK CONTROL S/C LINK K-G L-B C-G H-J D-B K-H L-B D-H L-B D-H C-B D-G K-G EXT SIG EXT SIG to G C-B K-B 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.
MODE AMPLITUDE CONTROLLED MIXING (2) As above, but the external signal will be summed with the main signal, but this time under control of the same, or another, external control input. SUBTRACT S/C LINK CONTROL S/C LINK EXT SIG to G (sum) EXT SIG to B (control) 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.
Barrier Strip Applications Fig 15.
16.0 Troubleshooting Problem: Solution: No Output Is the Mains Power connected (See section 8) Check the connections. See fuse failure (below). Do you have an input signal? Check the Input and Output connections (See section 9) Are the power amplifiers switched on? Problem: Solution: Fuse Failure The mains supply fuse is unlikely to blow without an electronic fault being present (See section 8).
Glossary 17.0 Glossary Active Active electronic circuits are those which are capable of voltage and power gain by using transistors and integrated circuits. Passive circuits are those which use only capacitors, resistors, transformers, etc. Amplitude Refers to the voltage level or intensity of a signal, and is usually measured in voltage or decibels. Attack Time The amount of time taken for the compressor or limiter to start gain reduction once the input signal has exceeded the threshold level.
dBV Distortion Drop-in Equalisation The same scale as for dBu as before, except that 0dBV = 1.0 Volts. Any modification of a signal which produces new frequency components not presents in the original. Harmonic distortion refers to added frequencies that are overtones to the fundamental frequency. Intermodulation distortion refers to added frequencies that are sum and difference values derived from the beating together of two frequencies.
Glossary Release Time Sibilance The distortion caused by large high frequency signals superimposed onto a normal signal, such as the 'sss' sounds of human voice. Threshold The pre-settable level above which a compressor or limiter will commence to gain reduce. Transient A sudden burst of energy in an audio signal which only lasts for a small period of time relative to the rest of the signal.
Specifications 18.0 Specifications General Input Impedance: 10k ohm balanced or unbalanced. Input Headroom: >+20dBv. Input CMMR: Better than -50dB 30Hz-20kHz. Typically -65dB at 1kHz. Output level: >+20dBv into 600 ohms or greater. Output Impedance: <1 ohm unbalanced. Output Gain: ±20dB continuously variable. Frequency Response: ±1dB 25Hz to 20kHz. Ultrasonic filter -3dB at 30kHz. Noise: Equivalent input noise <-86dBv 22Hz to 22kHz <-82dBv CCIR weighted.
Specifications Peak Limiter Threshold Range: +4dBv to +20dBv continuously variable. Ratio: >20:1. Attack Time: 150 microseconds, fast setting. 750 microseconds, slow setting. Release Time: 100 milliseconds, fast setting. 500 milliseconds, slow setting. Notes Note 1: Harmonic distortion will increase with reduced frequency and shorter time constants, which is inherent in this type of equipment.
Stereo Switch (Rear Panel): Couples channel 1 and channel 2 control signals for stereo operation. Indicated on the front panel by an LED. Rear Connections: INPUT: XLR 3-31 or equivalent (Balanced) OUTPUT: XLR 3-32 or equivalent (Unbalanced) 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.
Warranty Information 19.0 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.
Index Index A Attack Time Auto Time 8, 19 20 B Below Threshold. See Compression meters; Compression meters: Below Threshold Bypass switch 21 C Compression Compression meters Below Threshold Gain Reduction Input Level Meter Input 7 22 22 22 22 D De-essing Broadband HF with Full Dynamic Control HF-Only Wide with Full Dynamic Control Wide with Simultaneous Compression Dynamic Range 9, 25, 26, 30, 31 25 31 26 30 30 5 E Earthing 10 F Front Panel Fuses.
Index M Mains Connection Meter Input. See Compression meters: Meter Input Mode switch MON S.C. switch 15 21 24 O Operation Compression De-essing Output Connections Output Level. See Compression meters: Input Level 29 29 29 16 P Peak Limiter Switch Peak Limiting Power ON. See Mains Connection 17 9, 27, 31 R Rack space..
User Notes 47
User Notes 48
