DPR 944 User Manual 1
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Contents Contents 1.0 Mechanical installation 5 2.0 Unpacking 6 3.0 Mains Power Connection Mains Power 6 6 4.0 Introduction 7 5.0 5.1 5.2 5.3 Audio Connections Main Inputs Main Outputs Key Insert 10 10 10 11 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 Control Operations - Gate Gates In Key filter Filter narrow Key listen Threshold Depth 20dB Attack slow Release Stereo link Open/Shut LEDs Key insert connector 12 12 12 12 13 13 14 14 15 15 16 16 7.1 7.
Contents 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10 9.11 10.0 10.1 10.2 10.3 10.4 11.0 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.
Mechanical Installation 1.0 Mechanical installation A vertical rack space of 1U (1 3/4"/44.5mm high) is required, with a depth of 190mm, excluding connectors. Ventilation gaps are unnecessary. If the unit is likely to undergo extreme vibration through extensive road trucking and touring, the unit must be supported at the rear and/or sides to lessen the stress on the front mounting flange.
Unpacking Mains Power Connection 2.0 Unpacking As part of the BSS system of quality control, we check every product carefully before packing to ensure that it reaches you in flawless condition. Before you go any further, please check the unit for any physical damage and retain the shipping carton and all relevant packing materials for use, should the unit need returning.
Introduction Note: For USA and Canadian users, the replacement fuse must be of an identical UL rated type fuse for continued compliance with safety standards. 4.0 Introduction The BSS Audio DPR 944 is a FOUR channel unit containing two channels of ADVANCED GATING and two channels of PARAMETRIC COMPRESSION. Both channels of the gate may be stereo linked, as can both channels of the compressor. At all times the gate and compressor sections operate completely independently.
The DPR 944 Fig 4.1 Front Panel Fig 4.
All numbers in bubbles refer to Section numbers.
Audio Connections 5.0 Audio Connections 5.1 Main Inputs There are 2 input sockets on the rear panel of the DPR 944, Inputs 1 and 2. Each is electronically balanced on standard 3 pin female XLRs at an impedance greater than 10k Ohms. The ‘HOT, + or in phase’ connection is to pin 2 and the ‘COLD, -, or out of phase’ connection is to pin 3. Pin 1 is internally connected to the chassis earth via a low value capacitor. This ensures freedom from ground loops whilst allowing good EMC performance.
When using the DPR 944 to drive unbalanced inputs, best performance is usually obtained by connecting the DPR 944s ‘+’ signal to the equipment signal pin and the ‘-’ signal to the equipment shield. Fig 5.4 The DPR 944 shield should normally be connected to the equipment shield, preferably at the equipment end. 5.3 Key Insert Both the external key input and key send signals are available on a single ‘normalising’ TRS jack socket, wired as follows: Fig 5.
Control operations - Gate Control operations 6.0 Control Operations - Gate 6.1 Gates In When the Gates In switch is in the out, non illuminated position, all DPR 944 functions are bypassed and the input is connected directly to the output with a high quality relay. The same condition occurs when the power is off, and ensures that signal is passed through the unit in the case of a power or fuse failure. When the switch is depressed, the processed signal is present on the output.
This switch adjusts the width of the internal key filter. This filter should be considered as a pair of tracking high pass and low pass filters, with the space between them controlled by this switch. With the switch out, the filter has an approximate width of 3 octaves, but when depressed the width goes down to approximately 0.5 of an octave.
Control operations - Gate In normal use the threshold control is generally set so that wanted signal peaks are just able to trigger the gate, this gives the maximum protection from false triggering by undesired signals. 6.6 Depth 20dB With the gate ‘open’, the program can pass through DPR 944 unhindered. When ‘shut’, the level of the program passed is selected to be either approximately -80dB with the depth switch out, effectively no signal at all, or -20dB with the switch depressed.
6.8 Release This is a dual mode control, introducing hold as well as release. The hold time is determined internally to be about 20% of the selected release time. Hold A short hold time is required to avoid the DPR 944 from starting another attack sequence if the key signal momentarily falls below the threshold level. The hold time is reset every time an above threshold event is detected.
Control operations - Gate 6.10 Open/Shut LEDs If the gate is not passing program, the shut light is illuminated. If it is passing program, the open light is illuminated. These lights fade from one to another during the attack and release times, their relative intensity giving a visual indication of the dynamic response of the gating action. One thing to remember is that during the attack and release phases, as stated earlier, the DPR 944 uses a logarithmic control law to give a smooth fade to the sound.
General guide to gating 7.0 General guide to gating 7.1 What are gates for? Put simply, a noise gate is a device that blocks or switches off a signal, if that signal falls below a certain preset level. This works because the ear is much more sensitive to noise in the absence of other signals. Originally noise gates were used for just that, gating or removing noise from recordings. For example, traffic rumble in studios, or noise from old tape loop echo chambers. Figure 7.
General guide to gating prevent this. They are set up to open only when their particular drum is hit. Unfortunately it is sometimes not easy to set a gate up to only trigger on the desired signal, quite often the wanted and unwanted signals are close to each other in level. This is where key filters are useful.
• Now gradually rotate the threshold control anti-clockwise. At some position you will hear your signal appear - the gate has now ‘opened’. Notice also that the green open light has come on. Spend a few minutes adjusting the threshold control and watching the display. • Depress the depth switch whilst listening to the program. Notice that with the switch in, the signal does not completely disappear when the gate is ‘shut’.
Application examples - Gates 8.0 Application examples - Gates Each of the following application examples is accompanied by a front panel control diagram. Controls that are not highlighted should be set to the value shown - refer to the text where no initial setting is shown. Those controls which are highlighted can be set to any value, and are not critical to the given example. Settings can apply to both channels, but only one is shown here for clarity. 8.
Select some music with a heavy beat, set the key filter and filter narrow controls so that the beat notes are prominent. When you are happy with the filter controls, release the key listen switch. Now adjust the threshold control, you should now hear the beats in the program. Experiment with the key filter, filter narrow, attack and release controls to extract other sounds in the program.
Control operations - Compressor 9.0 Control Operations - Parametric compressor 9.1 Comps in When the Comps In switch is in the out, non illuminated position, all DPR 944 compressor functions are bypassed, and the input is connected directly to the output with a high quality relay. This is the same condition that occurs when the power is off, and ensures that signal is passed through the unit in the case of a power or fuse failure. When the switch is pressed, the processed signal is present on the output.
In use the threshold and ratio controls are generally adjusted as a pair whilst listening to the result. The release fast switch also changes the characteristics. 9.3 Ratio The effect of the ratio control can be shown on a graph which plots input level against output level, as shown in figure 9.1. This clearly shows that below threshold the DPR 944 acts purely as a linear amplifier. Fig 9.
Control operations - Compressor Fig 9.2 Effect of 'Progressive knee' compression 9.4 Release fast With the release fast switch in the out position, the DPR 944 operates in an auto mode. This feature of the DPR 944 is provided to overcome some of the conflicting setting requirements associated with conventional attack and release controls. The DPR 944 automatically adjusts itself to provide the required attack and release time settings, dependant on the program content.
9.5 Gain As compression is a gain reducing process, the output signal level will often be less than the input. The gain control is provided to restore the output signal to the desired operating point, and provides a range of +/-20dB relative to the input signal.
Control operations - Compressor The centre frequency of the band of interest is selected with the frequency control. Depressing the side chain listen switch makes the operation of this control audible, aiding its setting on exactly the signals of interest. 9.8 Width This control is used in conjunction with the frequency control to set the width of the parametric filter.
If the DPR 944 is being used with the width control in any position other than out, both the width and frequency controls on each compressor must be in the same positions for correct operation. 9.10 Below threshold meter The five LEDs of the below threshold meter give an indication of where the input signal is in relation to the start of compression.
General guide to compressing 10.0 General guide to compressing 10.1 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.
Fig 10.2 Operating level and headroom noise performance without incurring distortion. This device is called a compressor or limiter, two such devices are provided in the DPR 944. 10.2 Compressors & 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.
General guide to compressing 10.3 The effect of compression & limiting on sound 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 10.3a High threshold level Fig 10.3b Lower threshold level 10.
increased. 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. I.e. Limiters do not make-up the gain reduction. The range provided by the DPR 944 on its ratio and release controls is sufficient to allow its use either as a compressor or limiter. For limiter applications, the release fast switch should generally be out.
Application examples - Compressors 11.0 Application examples - Compressors Each of the following application examples is accompanied by a front panel control diagram. Controls that are not highlighted should be set to the value shown - refer to the text where no initial setting is shown. Those controls which are highlighted can be set to any value, and are not critical to the given example. Settings can apply to both channels, but only one is shown here for clarity. 11.
11.3 De-essing, Depopping & reducing proximity effect 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 can result in distortion. Selective high frequency compression can be used to help control this. High frequency compression is generally called de- essing, as it removes the ‘sss’ content from the program.
Application examples - Compressors Fig 11.2 Difference between Bell and shelf de-essing A related problem called ‘popping’, caused by wind from the ‘p’ sound entering a microphone, is responsible for generating large amounts of explosive bass signal. To treat this, configure the DPR 944 as for de-essing, but set the frequency control to select low frequencies. Fig 11.
11.4 Guitar treatment A general problem encountered with acoustic guitars is the difference in mid range signal level produced when the guitar is strummed relative to the amount when it is picked. The DPR 944 can be configured to reduce this problem. Start by setting the frequency control to 1kHz, width to 3 Oct, and the ratio control to 3 o’clock. While picking some notes, set the threshold control so that the below Fig 11.
Application examples - Compressors With some program playing, depress the side chain listen switch. By manipulating the sound system level and DPR 944 frequency and width controls, find the frequency band that is causing problems, and then make this band as narrow as possible. Ensuring that the threshold control is out, release the side chain listen switch and increase the system sound level until there is unacceptable distortion. Rotate the threshold control until the distortion is diminished.
Warranty Information 12.0 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.
Specifications 13.0 Specifications Gate General Input impedance Input CMRR Main output level Main output impedance Key output level Key output impedance Key input impedance Frequency response Noise Crosstalk Distortion 10k Ohm balanced or unbalanced >40dB 30Hz-20kHz >+20dBu into 600 Ohms or greater <50 Ohms balanced or unbalanced >+20dBu into 1k Ohms or greater 100 Ohms unbalanced 10k Ohm unbalanced +/-0.25dB 20Hz-20kHz -95dBu 22Hz to 22kHz <-85dB 20Hz to 20kHz <0.
Index Index A Application examples compression gating Attack slow Audio connections inputs key insert outputs E Effect of compression on sound 32 20 14 10 10 11 10 36 28 17 27 C Compressing beginners guide Compression broadband effect on sound frequency selective Compressor control Below threshold meter Comps in Frequency Gain Gain reduction meter Ratio Release fast Side chain listen Stereo link Threshold Width Comps in Connections audio Creative use 28 32 30 31 27 22 25 25 27 23 24 25 26 22 26 22 10 3
Index Key listen 13 L LED Below threshold meter Gain reduction meter open/shut Voltage selection 27 27 16 M Mains connection 6 O Open LED Outputs 16 10 P Peak limiting Proximity effect reducing 32 33 R Rack dimensions Ratio Rear Panel Release Release fast 5 23 8 15 24 S Shut LED Side chain filter use as EQ Side chain listen Specifications Stereo link 16 36 25 38 15, 26 T Threshold compressor gate 22 13 U Unpacking 40 V 6 6 W Warranty Info.
User Notes 41
User Notes 42
