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BW Broadcast DSPXmini-AM Operational Manual Download Page 27

Getting The Sound You Want

27

G

ETTING

 T

HE

 S

OUND

 Y

OU

 W

ANT

While the DSPXmini-AM can help you obtain the sound that you want we must always take into account the limi-
tations presented by the transmission channel. The biggest problem we have is the maximum peak level that can 
be handled by that transmission channel. 

The trade off in any audio processor is loudness vs. quality. The mark of how good a processor is how loud the 
processor can go while maintaining sufficient quality. It is up to you where this loudness / quality trade off point is 
set.

In the effort to squeeze as much bass and high frequency energy into the peak limited channel we must make 
compromises. If your aim is a cleaner sound and a slight loss of loudness is not important then it is easier to get 
the tonal characteristic you're after without distortion. Lower clipper drives will provide you with cleaner and less 
fatiguing sound. The choice is yours.

More LOUDNESS

Loudness can be increased in several ways.

Multi-band AGC:

Increase the drives to the bands.
Speed up the release times, making them faster.

While it is possible to create a strange response in the multi-band AGC, it is hard to produce distortion 
because whatever gets through the AGC is dealt with by the following peak limiters. 

Multi-band Limiters: 

Slow down the peak attack times, letting more through to the clippers.
Speed up the release times of the average release time constants. 
Slow down the average attack time so that the peak time constants dominate the control signal providing 
faster control.
Increase the master limiter drive.
Increase the individual limiter drives.

Extra loudness can be obtained by working on only a single or a couple of the above suggestions. You are 
likely to run into trouble if you 'CRANK UP' all of the above settings. You are likely to generate excessive dis-
tortion in the final clippers and generate a fatiguing sound if you're not careful. Less can be more. Make small 
changes and compare against the settings of the factory presets if you find you have lost your way some 
where.

Final clippers:

Increase the final clipper drive and increase its hardness control to a higher number.

WE SUGGEST ONLY SMALL MODIFICATIONS FROM FACTORY PRESET SETTINGS IF YOU ARE 
MODIFYING LOTS OF THE PARAMETERS. IF YOU ARE ADJUSTING ONLY A COUPLE FROM THE 
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.

Multi-band Limiters: 

Speed up the peak attack times, letting less through to the clippers.
Slow down the release times of the average release time constants. 
Speed up the average attack time so that the average time constants dominate the control signal providing 
slower control.
Decrease the master limiter drive.
Decrease the individual limiter drives.

Final clippers:

Decrease the final clipper drive.

Summary of Contents for DSPXmini-AM

Page 1: ...DSPXmini AM Broadcast Audio Processor Operational Manual Version 1 01 www bwbroadcast com ...

Page 2: ...Boost 12 Low pass filtering 13 The DSPXmini AM and its processing structure 14 Processing block diagram 15 The DSPXmini AM menu system 16 The menu structure 17 Processing Parameters 18 Setting up the processing on the DSPXmini AM 22 Getting the sound that you want 27 Managing Presets 29 Factory presets 30 Remote control of the DSPXmini AM 31 Remote trigger port 37 Security code lock 38 Clock based...

Page 3: ... maintenance repair work are expressly excluded from this warranty in particular if caused by improper handling of the product by the user This also applies to defects caused by normal wear and tear in particular of faders potentiometers keys buttons and similar parts Damages defects caused by the following conditions are not covered by this warranty Misuse neglect or failure to operate the unit i...

Page 4: ...her appliance including amplifiers that produce heat Power Source The appliance should be connected to a power supply only of the type described in the operating instructions or as marked on the appliance Grounding or Polarization Precautions should be taken so that the grounding or polarization means of an appliance is not defeated Power Cord Protection Power supply cords should be routed so that...

Page 5: ...electromagnetic compatibility Conformity is declared to those standards EN50081 1 EN50082 1 WARNING This equipment generates uses and can radiate radio frequency energy If not installed and used in accordance with the instructions in this manual it may cause interference to radio communications It has been tested and found to comply with the limits for a Class A computing device pursuant to subpar...

Page 6: ...was a desire to research the project for as long as necessary to get the job done We also knew that by combining the research with BW s embedded systems skills and ability to manu facture low cost cutting edge products we would ensure that the DSPX would be a winner The one aim to make an audio processor that offered all of the features found in the other more costly processors but at a fraction o...

Page 7: ...ware The Processing Architecture After input selection the 24 bit digital audio signal is passed through conditioning circuitry before being split to four bands by a phase matched crossover Each band is processed by multiband RMS leveller which corrects for input level variations and also improves consistency Each band is further processed by intelligent audio limiter The following distortion canc...

Page 8: ... FACE U3 CLASSICAL 3 A SAVE PRESET UP GO U1 BASS FACE U2 ROUND FACE U3 CLASSICAL 3 A INS DEL DONE NAME PRESET U2 MY PRESET 3 UP LOAD SAVE DSPXmini OUTPUT PROCESS INPUT D S P X m i n i A M ANALOGUE INPUTS AES EBU INPUT RS232 TRIGGER PORT LAN PORT GND LIFT MAINS POWER INPUT STATUS LEDS SOFT KEYS CONTROL KNOB DSPXmini AM FRONT AND REAR PANELS SYNC INPUT ANALOGUE OUTPUTS AES EBU OUTPUT ...

Page 9: ...dulation Multi band AGC The first four gain reduction meters show the gain reduction of the multi band AGC The range shown is 21dB to 21dB in 3dB steps There is only one meter per stereo channel and the value shown is the largest gain reduction of the left and right channels Under normal operation with a stereo audio feed this is fine but you may observe strange metering if the channels are not ve...

Page 10: ...nnect the audio outputs as required and set the output level settings for the analogue and digital outputs to match any external links or transmitters that require left and right audio inputs or an AES EBU input You can use the built in tone generator to set the output levels Navigate to Oscillator in the Output menu set it to Sine set the Amplitude to 60 and adjust Analog Out Level until your tra...

Page 11: ...rmed on the RMS level of the audio waveform and the ratio of compression is usually adjustable Compression is usually gated to prevent gain riding and suck up of noise during silence or quiet periods Limiting Limiting is a faster form of compression that employs faster time constants and higher ratios to produce a denser sound while controlling peaks based upon the peak level of the audio wave for...

Page 12: ...ial to compensate for the high end roll off by boosting the high frequencies in the processor This can help restore some of the high end response and brightness The DSPXmini AM has an HF equalizer that can provide as much as 20 dB of high end boost The graph below illustrates pre emphasis curves in 2 dB steps The blue curves show the response with the shape control set to 1 and the red ones show t...

Page 13: ...idth for Hybrid AM IBOC or 5 kHz bandwidth for Hybrid AM IBOC transmission set the filter to 10 kHz 7 5 kHz and 4 kHz respectively The graph below shows all the low pass filter curves You can use it to determine the correct setting for the required bandwidth or mask in your country Low pass filter curves 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 and 10 kHz DSPXmini low pass filters 100 00 20...

Page 14: ...t the audio spectrum into 4 bands while maintaining sonic transparency Multi band AGC The DSPXmini AM processes each band with RMS based levellers Each bands gain control processing function can be configured in different manners to provide different effects Adjustable timing constants drive and gating afford the user with full control of this important re equalisation stage of the processor Multi...

Page 15: ...C LOW AGC MID1 AGC HIGH AGC INPUT MB AGC LPF BPF BPF HPF BASS PEAK MID2 AGC LOW LIM MID1 LIM HIGH LIM MB LIM MID2 LIM LPF BASS CLIP LPF OUTPUT DSPXmini AM PROCESSING BLOCK DIAGRAM CLIP HF BOOST LP FREQ ASYMM ANALOG D A OSC DIGITAL SRC SYNC ...

Page 16: ...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 SYSTEM Contains all the system controls non processing such as remote control and securit...

Page 17: ...PING MENU MIXER BAND 1 MIX LEVEL BAND 2 MIX LEVEL BAND 3 MIX LEVEL BAND 4 MIX LEVEL MENU CLIPPERS BASS CLIP MAIN CLIP DIST CTRL FINESSE HARDNESS MAIN CLIP DRIVE MENU OUTPUT LP FILTER TILT EQ TILT FREQ ASYMMETRY POLARITY ANALOG OUT LEVEL MENU TONE GENERATOR OSCILLATOR FREQUENCY AMPLITUDE ANALOG OUT LEVEL MENU DIGITAL DIGITAL LEVEL SAMPLING RATE MENU SCHEDULE X REPRESENTS 0 7 TIME DAYPARTING ON OFF ...

Page 18: ... pseudo parametric style bass equalizer control that allows you to sweet tune the bass Four frequencies amplitudes and Q s are provided giving you 64 different bass curves to select from Frequencies selectable 60 Hz 76 Hz 95 Hz and 120 Hz Q s selectable 0 4 1 2 and 4 Gains selectable 0 dB 1 5 dB 3 dB 4 5 dB 6 dB HF SHAPE Shifts the HF boost curve lower values towards 1 or upper values towards 10 i...

Page 19: ...s the gain reduction of the band 3 the fast peak limiting time constant is still operating independently When this control is set to 0 there is no average gain reduction control and the fast peak time con stant is the only one controlling the level in the band 4 HF CLIPPING Negotiates the control of the high frequencies between limiting and clipping When the control is set towards 0 high end is pr...

Page 20: ...in the wiring STL etc resulting in the transmitter being modulated with more negative peaks than positive when Asymmetry control is set away from 100 this control can be used to easily fix the problem ANALOG OUTPUT LEVEL Controls the output level of the analogue output Range is 22 dBu to 14 dBu The TONE GENERATOR menu contains all the controls relevant to the tone generator oscillator OSCILLATOR T...

Page 21: ...tion of this manual OUTPUT LOCK This enables or disables the output code lock The options are enabled and disabled More information is available in the code lock section of this manual REMOTE SOURCE This selects the serial or the NET LAN port as the remote control method The default option is Off The LAN CONFIG menu contains the controls relevant to the LAN NET port IP Sets the IP address of the L...

Page 22: ... band AGC The multi band AGC in the DSPXmini AM employs an RMS based level detector for superior performance This enables the DSPXmini AM to control input level variations based on the true loudness of the input waveform unlike other simpler average responding peak detectors used in other digital audio processors When you couple the advanced detector with the user adjustable and hidden intelligent...

Page 23: ...e don t usually find much use for drives above 6dB but more may be required if other settings are adjusted to compensate In any case observe the peak limiter meters for a good indication of how much drive to use We don t recommend more than 9dB of gain reduction especially on bands 2 3 and 4 Gain reductions of 2 6dB are a good compromise between loudness and quality The multi band limiters in the ...

Page 24: ...peak attack time should be set to the desired attack time required from that limiter The range is 1 10 which corresponds to 1 to 200mS on an exponential scale The peak decay time should be set to the desired peak decay time required for transients The range is 1 10 which corresponds to a decay time of 10 to 1000mS The average attack time is perhaps the most important control in the dual time const...

Page 25: ...atio of the audio waveform none has the same effect on the peak to average ratio as the final clipper Great care is needed in setting the final clipper drive control This control needs to be adjusted carefully and only you can make the decision on the balance between loudness and quality As you increase the drive you will obviously obtain more loudness but at the expense of distortion There is a f...

Page 26: ...on Increase Tilt Gain and or adjust Tilt frequency until top is flat Flat top square wave correct no further tilt equalisation neeeded Square wave tilted too much tilt equalisation Decrease Tilt Gain and or adjust Tilt frequency until top is flat Tilt correction Asymmetry In some countries USA for example stations are allowed to modulate asymmetrically modulate positive peaks higher than negative ...

Page 27: ...average release time constants Slow down the average attack time so that the peak time constants dominate the control signal providing faster control Increase the master limiter drive Increase the individual limiter drives Extra loudness can be obtained by working on only a single or a couple of the above suggestions You are likely to run into trouble if you CRANK UP all of the above settings You ...

Page 28: ...U PROBABLY HAVE A BIT MORE LEE WAY IT IS VERY EASY TO LOSE YOUR WAY ONCE YOU START TWEAKING LOTS OF DIFFERENT SETTINGS More TREBLE HF We can obtain more high frequency energy in several ways The first is the use of a HF Boost equalizer It can provide as much as 20 dB of high frequency boost The HF CLIPPING and band 4 PEAK ATTACK are also controls that govern the amount of high frequency control di...

Page 29: ...w changed to a A button which if pressed will return you to the adjusted preset The other option you have if you don t press UP is the LOAD button reloading the saved preset and discarding your changes By using the but ton you can easily make processing adjustments quickly and hear instantly if the change is to your liking It is very easy to forget where you are sonically so the comparison feature...

Page 30: ... point for any format Fair not excessive amount of processing F3 GENERAL HEAVY A louder and more aggressive version of the General format Aimed for more competitive sound F4 TALK Optimised for talk radio and intelligibility Works good for all talk based format F5 TALK HEAVY A more louder and aggressive version of the Talk preset F6 NEWS A preset optimised for news talk Substantial amount of proces...

Page 31: ...ware new versions of DSPXmini AM code will also need to be uploaded into the DSPXmini AM via the serial port system The BW Broadcast development team have built the serial communications XMODEM pro tocol Any standard terminal program will allow you to send an update file into the DSPXmini AM via XMODEM protocol CONTROL OF THE DSPXmini AM BY RS232 SERIAL If you wish to use the RS232 port to control...

Page 32: ...urther information on the remote application is contained on the following pages If the DSPXmini AM remote application does not connect or disconnects after a few seconds then it could be that the password is incorrect The default password for the DSPXmini AM is 3779 You are free to change these on the DSPXmini AM itself see information on password control elsewhere in this manual PASSWORD ACCESS ...

Page 33: ...u should then see the menu tree in the left hand window see above image You can now navigate through the menu tree and see the controls that are contained in that menu appear in the main controls windows The example above shows the controls that are contained in the input menu Changing the processing is as simple as adjusting the sliders and buttons WORKING WITH PRESETS The DSPXmini AM remote appl...

Page 34: ...e in the list This will highlight the preset with a blue bar This does not change the preset or affect anything on the air All this blue selection bar indicates if that this is the preset that we want to perform an operation on We have two methods of performing the operation on the preset The first method is to click one of the icons at the bottom of the win dow These are from left to right Load p...

Page 35: ...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 two menu locations below it access two banks of four dayparts which make up the 8 dayp...

Page 36: ...2 00 05 00 factory preset 2 to run from 12pm everyday for 5 hours We could instead setup the dayparts as DPO F2 CHR ALL 07 00 10 00 factory preset 2 to run from 7am everyday for 10 hours DP1 U4 NEW PRESET ALL 10 00 02 00 user preset 4 to run from 10am everyday for 2 hours which saves a daypart position By carefully selecting the default preset and overlaying dayparts we are able switch presets sig...

Page 37: ...iggered by that pin If more than one pin is pulled low at the same time the pin with the lowest number will take priority E G if all pins are pulled low trigger 1 will take priority Once the trigger pin disconnects from the earth return connection the processor will return processing to the normally active preset Relays contact closures open collector and other hard wiring arrangements can be used...

Page 38: ...u and set the code lock option to ena bled Confirm the current password The lock will engage after four minutes of no front panel control system activity Disabling the security code lock feature Navigate to the system menu and set the code lock option to disa bled Confirm the current password Changing the lock codes Once locked the DSPXmini AM will not allow processing adjustments or access to the...

Page 39: ... and with the same control set the preset to switch to when the daypart triggers when the daypart start time matches the system clock You can also set the start time trigger of each daypart and set the length that the daypart shall be the time the trigger shall remain in force The start time has a day option and this can be set to ALL which would mean that the daypart would trigger every day at th...

Page 40: ...ating and symmetrical A D Conversion 48 kHz 24 bit 128x oversampled delta sigma converter with linear phase anti aliasing filter Filtering RFI filtered Analog Audio Output Configuration Stereo Source Impedance 10 Ohm electronically balanced and floating Load Impedance 600 Ohm or greater balanced or unbalanced Output Level 100 peak modulation Adjustable from 22 dBu to 14 dBu peak into 600 Ohms or g...

Page 41: ...anel 19200 kbps RFI supressed Ethernet Port 10 Mbit sec on RJ45 female connector RFI supressed Remote Control trigger port DB9 opto isolated and floating Eight pull low inputs Other Voltage 100 240 VAC 50 60 Hz 25 VA Connector IEC detachable 3 wire power cord supplied RFI supressed Grounding Circuit ground is independent of chassis ground and can be isolated or connected with a rear panel switch D...

Page 42: ...BAND 3 DRIVE dB dB dB dB ATTACK DECAY GATE dB dB dB dB BAND 4 DRIVE dB dB dB dB ATTACK DECAY GATE dB dB dB dB MB LIMITER MASTER DRIVE dB dB dB dB BAND 1 DRIVE dB dB dB dB PEAK ATTACK PEAK DECAY AVERAGE ATTACK AVERAGE DECAY BAND 2 DRIVE dB dB dB dB PEAK ATTACK PEAK DECAY AVERAGE ATTACK AVERAGE DECAY BAND 3 DRIVE dB dB dB dB PEAK ATTACK PEAK DECAY AVERAGE ATTACK AVERAGE DECAY BAND 4 DRIVE dB dB dB d...

Page 43: ...IX LEVEL dB dB dB dB CLIPPER BASS CLIP LEVEL dB dB dB dB MAIN CLIP DIST CTRL FINESSE HARDNESS MAIN CLIP DRIVE dB dB dB dB OUTPUT LOW PASS FILTER kHz kHz kHz kHz TILT EQ dB dB dB dB TILT FREQ Hz Hz Hz Hz ASYMMETRY POLARITY ...

Page 44: ...www bwbroadcast com ...

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