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BCL20 - User manual

1. S How al 240 A C 50Hz Disconnect fam mans bdag remaving caver BCL20 rear view showing Channel 2 and Mains connections The input and outputs of the BCL20 are on XLR connectors For balanced input and outputs connections to the unit should be wired as follows XLR 4dBu Pin 1 Screen Signal ground Pin 2 Hot ve Pin 3 Cold ve For unbalanced operation join pins 1 and 3 on either input or output The Side chain connectors are on 1 4 inch TRS jacks and are wired as follows TRS jack Tip Send Ring Return Sleeve Screen signal ground 3 WARRANTY Your LA Audio BCL20 has been manufactured to a high standard using guality components If correctly installed and operated the unit should give years of problem free operation However in the event of a defect in material or workmanship causing failure of the unit within one year of the date of original purchase we will agree to repair or at our discretion replace any defective item without charge for labour or parts To receive service under this warranty it is necessary to return the unit to an LA Audio authorised service centre or to the factory with a dated receipt as proof of purchase After repair the unit will be returned to you free of charge Limitations This warranty does not cover damage resulting from accident or misuse The warranty is void unless repairs are carried out by an authorised service centre The warranty is void if the unit has been modi
2. auxiliary send The other controls must be set as to be inoperative it is sufficient to set the Threshold at its maximum value L aoe a i i St LM cn ali vise gtr ah 2 H i E 14 ff I gt H L A E i 1 i 4 ja q f gt H kd E uuu bee ee De De be BANNED RS he eis pe KIE rah SATE Siew gulls ang goes Tap Garaget ap ted me 12 The following two applications show the BCL20 inserted into an individual channel After processing the signal is mixed with the other channels This is done because the BCL20 is used to modify a sound not to control its amplitude The next two applications show the BCL20 connected at the output of the mixer This is because if the BCL20 was inserted in the Mix inserts the level would vary with the setting Of the Master fader a CO 1441 ZHANNEL2 Cassette Mastering FM Transmission 13 Frequency Response 20 Hz to 20 kHz Signal to Noise Ratio 4 dBu Input 4 dBu Output Input Impedance Output Source Impedance Output Load Impedance Maximum Input Level Maximum output Level Total Harmonic Distortion THD 4 dBu Output 1 kHz 10 dB compression 1 kHz by pass Intermodulation Distortion Compression Ratio Attack Time Peak Continously variable Release Time Peak Continously variable Attack Time RMS Program dependant Release Time RMS Program dependant Mains
3. specific freguency conscious processing RFI protection has been a main concern in the design of the BCL20 allowing its use in broadcast installations 2 0 INSTALLATION IMPORTANT PLEASE READ THIS SECTION BEFORE USING THE BCL20 2 1 INSPECTION AND UNPACKING The BCL20 has been carefully packed at our factory in a carton designed to withstand handling in transit Should the unit appear to have been damaged in transit notify your dealer immediately and do not discard any of the packing The carton should contain The BCL20 unit Power cord e Operator Manual this book 2 2 OPERATING ENVIRONMENT The BCL20 is designed to operate between 0 and 50 C 32 122 F with relative humidity no more than 80 Should the unit be installed in an equipment rack ensure that the ambient temperature conforms to these levels 2 3 CE STANDARDS AND THE LOW VOLTAGE DIRECTIVE LVD The BCL20 has been designed to meet the latest Electromagnetic Compatibility EMC regulations However we recommend you do not operate the unit close to strong emitters of electromagnetic radiation such as power transformers motors mobile telephones or radio transmitters The unit should only be connected to a power supply of the type described in 2 4 POWER REQUIREMENTS or as marked on the unit The unit must be earthed for safe operation Disconnect the mains supply before removing the cover 2 4 POWER REQUIREMENTS There is a mains fuse located inside the un
4. AUDIO rte 21 Dual Stereo Broadcast Compressor Limiter Operation Manual August 2004 Introduction Installation Warranty Description of controls Applications Specifications Front panel blanks CONTENTS Page 2 Page 3 Page 5 Page 6 Page 8 Page 14 Page 16 1 0 INTRODUCTION The BCL20 is a stereo compressor limiter with a de essing capability which allows the end user to process two different signals or one stereo program Applications include FM transmitter protection disc mastering SPL limiting in PA and discotheque applications tightening of drums and sustain control on guitars and bass Main parameters including threshold gain attack and release times and compression ratio are user controllable A unique feature of the BCL20 is the continuously variable detection characteristics A potentiometer allows mixing of RMS and Peak detectors to tailor the timing parameters to the program being processed The BCL20 takes advantage of a unique transformer distortion cancelling circuit reducing it an order of magnitude compared to conventional designs 2 bargraphs display the amount of compression and the input output level The de essing functions involves a slew rate sensitive network which while keeping operation very simple allows frequency conscious compression in accordance with FM transmission or disc mastering pre emphasis A rear panel jack allows insertion of an external equaliser to achieve more
5. en it is desirable to preserve a relationship with the original dynamics but higher ratios provide useful effects particularly in pop recording and the transmission of speech where the main sound source needs to be brought out clearly This is effectively increasing the loudness of the signal and this enhances its prescence in a recording or over a background Attack and Release time Attack and release times are important when using compression since they determine the moment to moment gain change in a system and therefore the apparent loudness A fast release time combined with a high ratio will bring more of the lower level signal content up towards peak level and a fast attack time will really bring out the prescence However this kind of setting can sometimes be heard to be breathing or pumping This is the effect where the main sound source is intermittent and you notice the compressor working Suddenly the main voice comes through and sounds veryfull and then as it pauses the compressor turns off allowing the back ground noise to be heard and then the voice cuts in again immediately obscuring the background In these cases it may be necessary to either reduce the times used or reduce the ratio depending upon the effect required Modulation If more than about 6db of compression is used it is desirable to treat individual sound sources or groups of similar sound sources separately in order to avoid modulation effect
6. fied other than at the manufacturers instruction The warranty does not cover components which have a limited life and which are expected to be periodically replaced for optimal performance We do not warrant that the unit shall operate in any way other than as described in this manual DESCRIPTION OF CONTROLS GAIN REDUCTION DISPLAY This 12 Led bargraph indicates the amount of compression in dB The law is expanded at low values LEVEL DISPLAY This 12 Led bargraph indicates either the input level or the output level as selected by the input output toggle switch The bargraph can also be switched between peak and VU BYPASS This switches the compressor in and out of circuit so that comparisons may be made between the compressed and uncompressed signal IN OUT This switches the second bargraph display between input and output level DS IN OUT This button instantly adds de essing capability to the BCL20 by adding a filter into the side chain This makes the compressor frequency conscious which means that it compresses more on the frequency chosen in this case the frequency where sibilance occurs RATIO This determines the ratio of compression applied This may be varied from 1 1 to LIMIT 20 1 The ratio of compression may be defined as the ratio which determines how much the output is allowed to increase by in comparison to an increase of the input For example with a 10 1 compression ratio once the inpu
7. it which is accessed by removing the cover This fuse is for protection against unit faults and as such will not normally need replacing If you think you have a power related problem please refer to your dealer The voltage and fuse rating have been factory set for 230V 100mAUK 220V 100mA Republic of Korea 115V 200mANorth America The correct voltage and fuse rating is indicated on the rear panel e Please check that your unit is correctly rated for the voltage of the country of operation If the fuse requires changing at any time please ensure the correct fuse is fitted An incorrect fuse could cause damage to the unit and may constitute a fire hazard If you carry your BCL20 from one country to another it is very important to ensure the voltage is compatible For your information the unit can be internally rewired for use in 230V or 110 125V countries contact your dealer for information A special 100V version is available for Japan and a 220V 60Hz version for Republic of Korea The mains lead connections to the appliance are coloured in accordance with the following code Green and Yellow Earth Blue Neutral Brown Live WARNING THIS APPLIANCE MUST BE EARTHED 2 5 EXTERNAL CONNECTIONS Man vactured in the UK by L adiizian af SCY Electranics Ud OUTPUT CHANNEL 2 INPUT ON SERIAL NUMBER O li O E 1 SIDECHAIN Q Q 1 I we AN This equipment must be asrthad harides POWER ser senioeable pats inside y C
8. ite large changes in the input level above the threshold point Compression ratio The ratio in dB of input level change to output level change above the threshold point A 4 1 compression ratio implies that the output level will only change by 1dB for every 4dB that the input level changes above the threshold point Threshold This is the point at which compression starts to be applied as the signal rises or starts to be removed as the signal falls The Gain Reduction display will indicate when compression commences and then the threshold can be varied to obtain the desired effect Reducing the threshold point will give more compression effect than leaving it just below the input level Peak detection It is closely related to the maximum electric amplitude of the signal This characteristic is ideal for compressor limiters used in protection of transmission lines amplifiers broadcast transmitters etc RMS Detection It is related to the psycho acoustic perceived loudness This characteristic is more suitable for creative applications such as drums fattening bass sustain vocal processing etc De essing Reducing or removing the sibilance effect produced by some microphones some people and certain sound sources This is achieved by making a compressor frequency conscious This means that a pre emphasis filter is placed in the side chain which controls the compressor making it work harder upon those partic
9. power Consumption 115 220 VAC 50 60 Hz Meter Calibration Maximum Gain Reduction 6 SPECIFICATIONS 0 5dB 94 dB 20k Ohms balanced 20 Ohms 600 Ohms to infinity 20 dBu 600 Ohms Load 1 kHz 20 dBu 0 07 0 01 0 01 Continously variable from 2 1 to 20 1 from 0 1 to 70 millisec from 100 millisec to 3 sec Typ 12 ms for 12 dB Typ 4 ms for 24 dB Typ 120 ms for 12 dB Typ 240 ms for 24 dB 6 Volts amps 0 Vu 4 dBu more than 50 dB 14 DS Action 12 dB at 8 kHz Input Connector XLR 3 pin balanced Output Connector XLR 3 Pin balanced Dimensions 483mm W x 190mm D x 44 5mm H 19 W x 7 5 D x 1 75 H Weight 3 9kg 8 6lbs Shipping Weight 4 8kg 10 6lbs Temperature Range Operating OC to 50C Storage 30C to 75198 gt C Note In these specifications 0 dBu is referenced to 0 775 V RMS LA Audio reserves the right to alter any feature or specification without prior notice E amp OE 15
10. s when a dominant sound modulates the rest of the signal It is particularly difficult to limit low frequency sounds in a final balance because the effect on the remaining signal and ambience will be most noticeable Separate compression will increase the overall compression effect THE BCL20 AS A LOUDNESS LIMITER The perceived loudness SPL is not linear as a function of frequency The human ear is more sensitive to the mid frequencies than to very low or very high frequencies This phenomenon must be taken into account when using a limiter to control the maximum loudness in certain areas such as discotheques clubs and concert halls To emulate the typical loss of high and low frequency sensitivity of the human ear a weighting filter must be inserted in the side chain according to figurey1 This weighting filter is available from a number of companies manufacturing test equipment It must be set at C weighting high levels iat E 5 ks aot PINGI Aaa aaa ae a ANAA A 4 r i i Fig 1 10 As an alternative one can emulate such a filter using a stereo one octave equalizer set in such a way that the frequency response approximates that of figure 2 Fig 2 THE BCL20 AS AN ACOUSTIC NUISANCE LIMITER This is a complementary aspect of loudness limiting but in this instance the sound pressure level which must be limited is one that remains after attenuation and conduction outside the room or building where the so
11. t signal is above the threshold level the output will only rise by 1dB for every 10 dB that the input rises When the ratio is in excess of 10 1 the action of such large amounts of compression is described as limiting because the output is unable to exceed the limit imposed by the compressor THRESHOLD This adjust the signal level above which compression occurs The lower it is set the greater is the compression The threshold range is from 40 dBu to 20 dBu ATTACK This determines how fast the compressor will act upon the incoming signal This time may be varied from between 0 1 milli seconds and 70 milliseconds Caution Very fast attack times introduce distortion at low frequencies with ANY form of compressor This is caused by a low frequency signal being longer than the attack time The low frequency waveform will be distorted by the initial gain reduction because the action is almost certain to occur mid waveform RELEASE This determines how fast the action of the compressor will take to be turned off as the incoming signal falls below the threshold This time may be varied from between 100 milliseconds and 2 seconds Caution Very fast release times introduce distortion at low frequencies with ANY form of compressor This is caused by a low frequency signal being longer than the release time The low frequency waveform will be distorted by the initial release of gain reduction because the action is almost certain to occ
12. ular frequencies In true de ess mode the compressor ONLY acts upon those frequencies and passes all other ones GENERAL The usual purpose of Limiting and Compression is to increase loudness and to provide overload protection and generally to control level Limiting Limiting is used mainly to provide overload protection i e to limit the output to some desired output level The protection required is usually against transients which exceed the peak input level required for a tape recorder or a transmitter These high energy transients are usually of very short duration micro seconds but may wreck a transmitter or ruin a good recording by introducing distortion Control of these transients by limiting does not noticeably affect the dynamic range since the gain reduction when it does occur is momentary and of a relatively low order of magnitude In most cases a fast release time will be employed so that the transients are controlled quickly without any apparent change in programme content This form of compression using ratios of 10 1 and above allows the engineer to reduce his system headroom and operate with a higher recording or broadcast level without fear of overload and thus increase the useable dynamic range of a recording or transmission system Compression Compression describes conditions of gain reduction that are more or less continuous so that the original dynamics are compressed A low compression ratio is used wh
13. und is produced Very often only certain low frequencies are transmitted in particular those which excite resonant modes of cavities walls or structures To achieve efficient limiting of those frequencies it is necessary to measure the noise transmission using a real time spectrum analyser preferrably 1 3joctave When this is done one has to copy the frequency response to a graphic equalizer which is inserted in the side chain In operation limiting will occure predominantly at those frequencies which create a nuisance NB To improve this scheme it may be necessary to use a parametric equalizer tuned precisely at the frequencies which excite resonances Sa eT fee meal ft PEE ETE ons 11 When this is done one has to copy the frguency response to a graphic equaliser which is inserted in the side chain THE BCL20 AS AN AUTOMATIC VOICE OVER DUCKER This application is useful in discotheques and radio where it provides an automatic fader which reacts to the voice of the disc jokeys reducing the background music accordingly To do this the music channels must be routed to separate groups which will be processed through the BCL20 and then reinjected to the Mix busses Sub group The voice channels must be routed directly to Mix and to an auxiliary output whichs feeds the Side Chain insert Return The BCL20 must be in the Stereo mode The active front panel controls are those of the channel receiving the
14. ur mid waveform RECTIFIER This controls the respective percentage of RMS detection and Peak detection that will be processed by the side chain In the extreme positions it uses only one of the rectifiers In the intermediate position it uses a blend of both A very basic rule of thumb would be to use RMS detection on individual tracks and Peak detection on mixed program see applications As always this is very much open to experimentation The unique continuously variable detection characteristic of the BCL20 makes experimentation as easy as turning a knob NB The Attack and Release controls relate to the Peak rectifier only Hence when the Rectifier control is in the full ccw position RMS these controls are inoperative GAIN This controls the output gain after compression and is used to match the output with the level of the incoming signal This may be varied from 20 dB to 18 dB STEREO DUAL The unit may be switched between stereo mode and two separate mono channels POWER On rear panel This switches the unit ON or OFF and the adjacent led lights when the unit is ON 5 APPLICATIONS DEFINITIONS OF TERMS USED Compressor A variable gain amplifier whose gain decreases as the input increases beyond a threshold point A compressor uses ratios of up to 8 1 Limiter A limiter is a compressor with very high compression ratios usually above 10 1 A high ratio maintains an almost constant output level desp

BCL20 - User manual

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