DSPX-FM Broadcast Audio Processor Operational Manual Version 3.11 www.bwbroadcast.
Table Of Contents Warranty 3 Safety 4 Forward 6 Introduction to the DSPX 7 DSPX connections 8 DSPX meters 9 Status LEDS 9 Quickstart 10 An introduction to audio processing 11 Source material quality 12 Pre-emphasis 12 The DSPX and its processing structure 13 The processing path 13 Processing block diagram 15 The DSPX menu system 16 The Menu stucture 17 Setting up the processing on the DSPX 25 Getting the sound that you want 36 Managing Presets 40 Factory presets 41 R
WARRANTY BW Broadcast warrants the mechanical and electronic components of this product to be free of defects in material and workmanship for a period of one (1) year from the original date of purchase, in accordance with the warranty regulations described below. If the product shows any defects within the specified warranty period that are not due to normal wear and tear and/or improper handling by the user, BW Broadcast shall, at its sole discretion, either repair or replace the product.
SAFETY INSTRUCTIONS CAUTION: To reduce the risk of electrical shock, do not remove the cover. No user serviceable parts inside. refer servicing to qualified personnel. WARNING: To reduce the risk of fire or electrical shock, do not expose this appliance to rain or moisture. This symbol, wherever it appears, alerts you to important operating and maintenance instructions in the accompanying literature. Read the manual.
Object and Liquid Entry: Care should be taken so that objects do not fall and liquids are not spilled into the enclosure through openings.
FORWARD Thank you for your purchase of the DSPX digital audio broadcast processor. Over the last decade the staff at BW have observed broadcast processors from afar with fascination and intrigue and shared a keen interest in digital audio processing. In January 2002 we decided on a whim that it was time to have a go at designing our own digital audio processor.
INTRODUCTION TO THE DSPX The BW DSPX is a new generation of digital audio signal processor that can be used to process audio ready for FM and digital broadcast. The DSPX is the first UK designed and manufactured multi-band digital broadcast processor. Using the latest multi-band DSP technology the DSPX offers a versatile and powerful tool in creating a loud punchy on-air presence.
Connections 8 ANALOGUE INPUTS ANALOGUE OUTPUTS SCA INPUT MPX PILOT OUTPUT OUTPUT HEADPHONE JACK L AES / EBU OUTPUT SYNC INPUT METERING L AES / EBU INPUT LOW MIDL MIDH HIGH dB dB LOW MIDL MIDH HIGH dB WB dB R 0 -1 -2 -3 -4 -5 -6 -9 -12 -15 -18 -21 R CLIP MPX RS232 & TRIGGER PORT % 110 100 90 80 70 60 50 40 30 20 10 PILOT OUTPUT USB PORT USB LAN PORT REMOTE DSPX INPUT PROCESS OUTPUT STATUS LEDS EDIT AES/EBU DSPX-FM FRONT AND REAR PANELS GND LIFT DSP X CLIP -2 -4 -6 -8 -
DSPX METERS The DSPX has 182 LEDS that provide ‘always on’ instant IO and processing metering.
QUICK START 1. Install the processor into the rack. 2. Connect AC power to the unit, and turn on the power. 3. Connect the analogue and / or digital audio inputs. 4. Select the analogue or digital input as the source of the processing with the 'INPUT SELECTION' parameter which can be found in the 'INPUT' menu. Apply audio and observe the input meters. For analogue inputs, adjust the 'INPUT’ menus 'INPUT LEVEL CONTROL' so that the input meters do not clip.
INTRODUCTION TO AUDIO PROCESSING Most audio processors use a combination of compression, limiting and clipping to 'funnel' the dynamic range down, reducing the peak to average ratio in each stage. A cascaded arrangement of compressor, limiter and clipper produces the best results. The first stage of processing usually operates in a slow manner, the processing getting progressively faster and more aggressive as the audio passes through the chain.
SOURCE MATERIAL QUALITY The DSPX-FM has the ability to substantially improve the quality of your ON-AIR broadcast. However the DSPXFM can only work with what you provide it. The best performance will be obtained when the DSPX-FM is fed with very clean source material. After dynamic multi-band re-equalisation is performed poor quality source material will sound poorer when processed with the DSPX-FM. We strongly advise against the use of MP3's and other compressed audio formats for audio storage.
THE DSPX AND ITS PROCESSING STRUCTURE The DSPX broadcast audio processor can be used for processing audio prior to broadcast on FM and digital radio services. Digital radio encompasses DAB,HD,IBOC and other radio based broadcasting as well as internet radio, known also as streaming. The DSPX can also be used effectively for audio post production and mastering, ideal for giving CD’s that HOT sound.
couplings and complex gating features afford the user with full control of this important re-equalisation stage of the processor. Multi-band Limiters Each band has its own dynamic peak limiter. Multiple time constant based detectors with built in adjustable hold and delay functions significantly reduce distortion. Mixer The four bands are 'virtually' mixed together at this stage. In truth, the four bands have become three. The three bands are fed off into the two peak processing paths.
Processing Block diagram 15 DIGITAL ANALOG SRC A/D P.R.
MENU SYSTEM OVERVIEW This section presents an overview of the four main menus and thier submenus and any parameters that are contained in them. INPUT: Contains all the controls that affect input selection, level control and signal conditioning. PROCESS: Contains all the controls that affect the processing. OUTPUT: Contains all the controls that affect output selection, level control and signal conditioning. SCHEDULE: Contains all the real time clock controls for switching presets (Dayparting).
COMPOSITE CLIPPER ADVANCED: DYNAMIC MB CLIPPING MAIN CLIP FINESSE OVERSHOOT CONTROL MAIN CLIP TYPE MENU STRUCTURE MENU: INPUT SOURCE STEREO MODE ANALOG INPUT LEVEL RIGHT TRIM INPUT FAIL SWITCH HIGH PASS FILTER PHASE ROTATOR PRE-EMPHASIS MENU: OUTPUT MENU: ANALOG MODE OUTPUT LEVEL DE-EMPHASIS MENU: DIGITAL MODE OUTPUT LEVEL SAMPLE RATE DE-EMPHASIS MENU: STEREO LEVEL PILOT LEVEL PILOT PROTECTION PILOT OUTPUT MENU: HEADPHONE LEVEL MENU: PROCESS MENU: WIDEBAND AGC DRIVE ATTACK DECAY GATE RTP LEVEL RTP SPEED
PROCESSING PARAMETERS The 'INPUT' menu contains all of the options and parameters relating to the control and conditioning of the audio inputs. 'SOURCE' This parameter allows you to select the between the analog and digital inputs as the source for the processing. 'INPUT MODE' This parameter allows you to select different mono options as well as the default Stereo option. There is also the ability to swap the left/right channels.
'GATE THRESHOLD' The gate function prevents 'suck-up' of noise during periods of silence or low level audio. The level can be adjusted to turn on when the input drops to a level from -20dB to -40dB. The gate can also be switched off or forced on. The gate when turned on will cause the gain reduction to move towards the level set by the RTR LEVEL control and to move towards that level at the rate set by the RTR speed control.
'ATTACK' Controls the attack rate of the AGC, The time the AGC takes to respond to an increase of input level. The attack time can be varied between 1 and 10 which corresponds to 100mS to 30S on a semi-exponential scale. 'DECAY' Controls the release/decay rate of the AGC, the time the AGC takes to respond to a decrease of input level. The DECAY time can be varied between 1 and 10 which corresponds to 100mS to 30S on a semi-exponential scale.
The 'MULTI-BAND LIMITERS' peak limit each of the bands to prevent distortion in the processors clipping peak control system. 'B1-4' 'DRIVE' Controls the drive into the limiter. The drive can be increased or decreased by up to 12dB. 'THRESHOLD' Sets the limiter threshold. If audio is below threshold, there will be no gain reduction. Audio signals that go above will be attenuated. Threshold level can be varied between -6dB to +6dB in 0.5dB steps.
'MIXER' menu. Each band can be adjusted over a small range to provide small EQ changes. These controls are limited in range to prevent excessive drive into the peak clipping stages and excess distortion being introduced. A solo mode is provided to aid in the setting up of parameters. BAND1MIX: -3dB to +3dB of level adjustment is available. BAND2MIX: -3dB to +3dB of level adjustment is available. BAND3MIX: -3dB to +3dB of level adjustment is available. BAND4MIX: -3dB to +3dB of level adjustment is available.
the main clippers output level. 'HF CLIP LEVEL' Controls the clip level of band 4. The clip level range is -12dB to 0 dB referenced to the main clippers output level. 'HF CLIPPING' This control redistributes band 4 peak control between the band 4 limiter and the HF clipper. The range is 0 to 17 with 0 equating to full control by the band 4 limiter and higher numbers producing less control by the band 4 limiter on a frequency dependent basis, leaving control by the HF clipper.
'DE-EMPHASIS' This controls the de-emphasis setting of the digital output. Options are Off, 50 μS (Europe) and 75 μS (USA) The 'STEREO' menu contains all the controls relevant to the DSP stereo encoder that generates the multiplex signal. 'OUTPUT LEVEL' Controls the output level of the composite MPX output. Range is 0dBu to +12dBu. 'PILOT LEVEL' This parameter sets the level of the composite signals 19 Khz pilot tone. The adjustable range is 6% to 12% and an OFF setting for mono applications.
SETTING UP THE PROCESSING ON THE DSPX This section has more detailed information on setting up the DSPX’s processing. The section is laid out in the same order as the processing route through the DSPX. High pass filter The high-pass filter has five selectable cut off frequencies and a bypass option. Most users will bypass the highpass stage but there are several cases where enabling the high-pass has an advantage. The first of those is stations that mainly play vinyl recordings.
The effects of time constant speeds AGC attacking and decaying with faster time constants AGC attacking and decaying with slower time constants this manual as 'forced gating' as it has the effect of switching the gate on at all times with any level of program material. This option is used to bypass the AGC and provide a fixed gain through it. The fixed gain (in dB) being that of the (input drive plus 12) minus the level in dB that the return to rest level is set at.
The last gating option available to the wideband AGC is window gating. Window gating is separate from the silence gating that we have been discussing in that it does not work on the amplitude of the audio, rather the peak to average ratio of the waveform and how the waveform is changing over time. The window gating feature if enabled freezes the gain over a pre-defined range and will only let gain control commence once the waveform has fallen outside of this pre-determined range.
Frequencies selectable: 60Hz, 76Hz, 95Hz and 120Hz. Q's selectable: 0.4, 1, 2 and 4. Gains selectable: 0, 1.5dB, 3dB, 4.5dB, 6dB. A starting setting of 95Hz, Q of 1 and gain of 4.5dB warms the bass up quite nicely but you are free to experiment to get the bass sound you're after. Additionally, bass tune control allows control of the 'flavour' of the bass by adjusting various points in the bass dynamic control system. Xover The Xover in the DSPX has two selectable frequencies per band split..
To force gate a band you need to set the gate threshold control for that band to 'ON'. You then need to adjust the RTR level to set the gain reduction in that band. The gain through the stage will equal ((BAND DRIVE in dB - 12dB) - RTR LEVEL in dB). For example to create unity gain you must make sure that the drive control is 12dB more positive than the RTR level IE: -12dB RTR with a drive of 0dB. Version 2 adds the facility to control how the multi-band AGC gating works.
balance between peak and average energy in the detector. With smaller numbers more energy is transferred into the average circuit and a higher platform level is created so more time will be spent releasing at the slower average rate. Higher numbers offer slower attack times for the averaging part of the detector and this has theeffect of lowering the average platform level and allowing the peak part of the circuit to dominate with its faster release times.
Without hold with hold Delay The delay control sets the amount of time the processor will hold the gain reduction for before releasing at the peak decay rate. Careful setting of this control allows us to speed up the peak decay time without introdudcing the audible effects of faster decay times. Setting this control to 1 is a neglible amount of delay before decay which is equivalent to the delay being switched out of circuit.
The mixer The post limiters mixer in the DSPX is not strictly a mixer but a band output level control where small EQ changes can be made. It has been called the mixer as most other processors have a mixer at this position and our VIRTUAL mixer does the same job. Bands 1 and 2 do mix together at this point so I suppose you could call it a half-mixer. The mix of band 1 and 2 is then fed off with the other two bands to the peak limiting paths for DR and FM. The four bands have become three.
level for the bass (mix of bands 1 and 2) and leave the remaining half for the sum mix of the mid-clipper and the HF-clipper. If these two clippers' clip thresholds were set so that they didn't add up to more than 50% modulation, say -12dB and -12dB then the main clipper would have no work to do as all of the peak control would be done with the multi-band clippers.
and distortion that your listeners will find uncomfortable to listen to especially for extended periods of time. We also suggest that you make final clipper drive adjustments in tandem with the multi-band clipper drive as what is taken from or added from one can usually be made up for with the other. The final clipper now has an additional control to help reduce IMD distortion.
may not be immediately obvious. The HF clipping control (located in the band 4 limiter and clippers menus) redistributes control of high frequency energy from the band 4 limiter into the following processing stage. For the FM path this HF energy gets handled by the HF clipper but in the case of the look-ahead limiter this high frequency energy can modulate the rest of the audio waveform and introduce a pumping type sound.
GETTING THE SOUND YOU WANT While the DSPX can help you obtain the sound that you want we must always take into account the limitations presented to us by the transmission channel. The biggest problem we have is the maximum peak level that can be handled by that transmission channel. For FM broadcast this is +/- 75 KHz for 100% modulation and for digital services, 0dBfs. The trade off in any audio processor is loudness vs. quality.
ABOVE SUGGESTIONS THEN YOU PROBABLY HAVE A BIT MORE LEE-WAY. IT IS VERY EASY TO LOSE YOUR WAY ONCE YOU START 'CRANKING' LOTS OF DIFFERENT SETTINGS. More CLARITY We can obtain extra clarity and quality in several ways. Multi-band AGC: Slow down the release times, making them slower. Increase the bands Ratio control so more control is performed and less is allowed to pass to the following peak limiter.
Slow down the peak attack time for band 1, letting more through to the clippers. Speed up the release time of the average release time constant. Slow down the band 1 average attack time so that the peak time constant dominates the control signal providing faster control. Decrease the band 1 HOLD level or turn it off. Decrease the band 1 Delay time Increase the band 1 limiter threshold, letting more through to the clippers.
Increase the band 4 look-ahead limiter attack time constant slowing down the attack of the secondary time constant circuit. Decrease the band 4 look-ahead limiter decay time constant speeding up the decay of the secondary time constant circuit. WE SUGGEST ONLY SMALL MODIFICATIONS FROM FACTORY PRESET SETTINGS IF YOU ARE MODYFYING LOTS OF THE PARAMETERS. IF YOU ARE ADJUSTING ONLY A COUPLE FROM THE ABOVE SUGGESTIONS THEN YOU PROBABLY HAVE A BIT MORE LEE-WAY.
MANAGING PRESETS (FRONT PANEL CONTROL) The DSPX-FM has an assortment of factory presets and provision for 8 user ones. While the factory presets may not suit your tastes you will generally find one that serves as a good starting point in creating your own custom preset. The preset facilities of the DSPX-FM are accessed from the three intuitive soft keys. Selecting a preset. First press the 'LOAD' button and then select the preset you want with the control knob.
FACTORY PRESETS The factory presets in the DSPX are not supposed to be de-facto standards by any means but are starting points for you to create your own user presets. It is impossible to create presets that will suit every format and market. What is right for one market is not usually right for another. The staff at BW will be able to help you refine your sound further if none of the factory presets meet your requirement. V3 contains the following factory presets. FM PRESETS.
F18 DR NATURAL LOUD A competitively loud sound which enhances the vocals. F19 DR NATURAL A nice balance of mids and highs provide a nice pleasing natural sound. Vocals stand out in the mix. F20 DR OVER THE TOP When loudness is more important than anything else, try this. F21 DR PRESENCE The vocals are brought to the front of the mix with this pleasing mid enhanced preset.
REMOTE CONTROL OF THE DSPX-FM In addition to the front panel LCD control system the DSPX-FM has a USB port, a serial port and an ethernet/ LAN port. These allow remote control of the DSPX-FM through a remote application program running on a windows based PC. The remote control program is available for download from www.bwbroadcast.com The USB port on the front panel of the DSPX-FM is a USB/Serial convertor module.
Remote application connection screen CONTROL OF THE DSPX-FM BY RS232 or USB (SERIAL) If you wish to use the RS232 or USB port to control the DSPX-FM follow the steps below 1. Connect the supplied serial cable to the rear RS232 port or a USB cable to the front USB port 2. Navigate to the ‘REMOTE SOURCE’ parameter (also in system) and select the serial option 3. Run the DSPX-FM remote application and you will be presented with a connection screen (see image).
Remote application connected PASSWORD ACCESS The DSPX-FM contains two levels of password control, a high level password which blocks access to all areas of the DSPX-FM and an ‘Output’ level password that allows access to all areas of the DSPX-FM except the output menus that contain the output mode and level settings.
Preset window shown WORKING WITH PRESETS The DSPX-FM remote application makes it easy to load, save and change presets. Click the preset button (top left) if not already depressed. You should then see the preset list in the left hand window (see image). Understanding the preset list The preset list contains all of the presets contained in the DSPX-FM. The user presets are prefixed U1 to U8 and the factory presets from F1 onwards.
Preset icons Load preset Load preset will change the default preset to the one selected. This usually means that this preset will become 'on air'. The exception to this is when the default preset is being overridden by a daypart or remote trigger. In this case the DSPX-FM will 'on air' the selected preset when the daypart or trigger hands back control to the default preset. Save preset Save preset will save the current on-air preset to the highlighted user preset position.
SCHEDULING WITH THE REMOTE APPLICATION Using the menu tree to change the processing is quite simple and really doesn't need a lot of explanation. The scheduling screens that controls the dayparting may appear daunting so we are going to give you a quick guide to using it. There are three menu locations for controlling scheduling. The first location is shown in the screen shot below and it contains the ON/OFF and time setting control.
The dayparts can be layered so that one can override another. Let's say the default preset was U1:MAIN PRESET and this was on the air all of the time. We want to change the preset from 7AM to 10AM every day of the week to F2:CHR and then from 10AM to 12PM we want U4:NEW PRESET and then back to F2:CHR until 5PM.
REMOTE TRIGGER PORT The system menu contains the remote trigger port option from where it can be enabled or disabled. If enabled the remote trigger port on the processor allows you to select any of the first 8 user presets by pulling one of 8 pins on the trigger port socket low. The rear panel trigger port socket is a 9 pin male D-type whose connections are shown below.
SECURITY CODE LOCKS The system menu contains the security code lock options from where they can be enabled or disabled. The DSPX-FM has two code locks, the main full lock and the output lock. When enabled the full code lock prevents editing of the DSPX-FM parameters. When enabled the output lock restricts access to the output menu section of theDSPX-FM.
CLOCK BASED CONTROL (DAYPARTING) Your processor contains a battery backed up real time clock that can maintain the current time and date even when the power has been removed. This allows users to switch between presets at specific times of the day or week. This is very useful on a multi-format radio station where one processing preset may not suit all of the formats of music that are broadcast.
SPECIFICATIONS Specifications apply for measurements from analog left/right input to stereo composite output and to FM analog left/right output. Measurements apply to FM mode of operation. Frequency Response (Bypass Mode): Follows standard 50μs or 75μs pre-emphasis curve ±0.10 dB, 2.0 Hz– 15 kHz. Analog left/right output and digital output can be user configured for flat or pre-emphasised output.
MPX output Source Impedance: 10 Ohm Single-ended, floating over chassis ground. Load Impedance: 600 Ohm or greater. Maximum Output Level: +12.0 dBu (peak) software-controlled output level control Minimum Output Level: 0dBu (peak)Software-controlled output level control Pilot Level: Adjustable from 6.0% to 12.0% and OFF, software controlled. Pilot Stability: 19 kHz, ±1 Hz (10 degrees to 40 degrees C).
APPENDIX Installing USB VCP Drivers To install the VCP drivers for the DSPXtra under Windows XP and XP SP1, follow the instructions below: If a device of the same type has been installed on your machine before and the drivers that are about to be installed are different from those installed already, the original drivers need to be uninstalled. Download the latest available VCP drivers from the www.audio-processor.com website and unzip them to a location on your PC.
Select “Install from a list or specific location (Advanced)” as shown below and then click “Next”. Select “Search for the best driver in these locations” and enter the file path in the combo-box (“C:\VCP Drivers” in the example below) or browse to it by clicking the browse button. Once the file path has been entered in the box, click next to proceed. If Windows XP is configured to warn when unsigned (non-WHQL certified) drivers are about to be installed, the following screen will be displayed.
The following screen will be displayed as Windows XP copies the required driver files. Windows should then display a message indicating that the installation was successful. Click “Finish” to complete the installation. This has installed the serial converter. The COM port emulation driver must be installed after this has completed.
The following screen will be displayed as Windows XP copies the required driver files. After clicking “Finish”, the Found New Hardware Wizard will continue by installing the COM port emulation driver. The procedure is the same as that above for installing the serial converter driver. Open the Device Manager (located in “Control Panel\System” then select the “Hardware” tab and click “Device Manger”) and select “View > Devices by Type”.
DSPX-FM v3 preset sheet Preset 1 Preset 2 Preset 3 Preset 4 INPUT SOURCE MODE ANALOG LEVEL INPUT FAIL HP FILTER PHASE ROTATOR PRE-EMPHASIS dBu dBu dBu dBu Hz Hz Hz Hz μs μs μs μs DRIVE ATTACK DECAY GATE RTP LEVEL RTP SPEED WINDOW GATING dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB DEEP BASS BASS TUNE BASS PEAK FREQ BASS PEAK Q BASS PEAK GAIN dB dB dB dB Hz Hz Hz Hz dB dB dB dB % % % % % % % % % % % % DRIVE ATTACK DECAY GATE RTP LEVEL RTP SPEED WINDOW GATING
MB LIMITER MASTER DRIVE LIMITERS RATIO B1<2 COUPLING B2>3 COUPLING B3>2 COUPLING B3>4 COUPLING L/R COUPLING % % % % % % % % % % % % % % % % % % % % DRIVE THRESHOLD PEAK ATTACK PEAK DECAY AVERAGE ATTACK AVERAGE DECAY HOLD DELAY dB dB dB dB dB dB dB dB dB dB dB dB DRIVE THRESHOLD PEAK ATTACK PEAK DECAY AVERAGE ATTACK AVERAGE DECAY HOLD DELAY dB dB dB dB dB dB dB dB dB dB dB dB DRIVE THRESHOLD PEAK ATTACK PEAK DECAY AVERAGE ATTACK AVERAGE DECAY HOLD DELAY dB dB dB dB dB dB dB dB dB
HIGH ATTACK HIGH DECAY OUTPUT STEREO LEVEL PILOT LEVEL PILOT PROTECTION 19kHz SYNC dBu % dBu % Appendix B - Preset Sheet 61 dBu % dBu %
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