MULTI PROCESSOR OPERATION MANUAL
Version - V1 April 2000 Page 2
CONTENTS Page 1. 2. 2.1 2.2 2.3 2.4 2.5 2.6 Introduction Installation Inspection and un-packing Operating environment CE standards Power requirements Signal levels External connections 3 4 4 4 4 4 5 6 3. Warranty 9 4. Description of controls 10-15 4.1 4.2 4.3 4.4 Input section Noise Reduction and Compressor section Equaliser section Output section 10 11 13 5. Applications 16-21 5.1 5.2 5.3 5.4 5.5 Input Compressor Expander Equaliser Output 16 16 18 18 20 6. Circuit description 21 6.
1.0 INTRODUCTION The MPX10 is a single channel processor designed for one step processing of vocal or solo instruments where the highest quality signal path is required. The MPX10 combines a Mic/Line preamplifier with DI input, Noise Reduction, 4 mode Auto Compressor and Equaliser in a compact 1U case. The MPX10 is an ideal front end for direct to tape or hard disk recorders and as a superior analogue input stage for digital work stations.
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2.0 INSTALLATION IMPORTANT: MPX10 PLEASE READ THIS SECTION BEFORE USING THE 2.1 INSPECTION AND UNPACKING The MPX10 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 MPX10 unit • Power cord • Operator Manual (this book) 2.
110V 100mA North America • The correct voltage and fuse rating is indicated on the rear panel. • 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 MPX10 from one country to another it is very important to ensure the voltage is compatible.
INPUT SECTION: M I C R O P H O N E XLR ground) Pin 1 Pin 2 Pin 3 Screen (Signal Hot (+ve) Cold (-ve) This is a low impedance (1.2k ), low level input designed to give the correct loading and sensitivity for dynamic type microphones. Plugging line sources into this input may load the connected equipment and may result in the loss of signal level, frequency range and increased distortion.
Sleeve Screen Tip Hot (+) Fig 2.6.4: DI Input connections This a high impedance (0.5M ) input primarily intended for connecting directly to electric guitars. O U T P U T jack Tip Hot (signal +) Sleeve Screen (signal ground) This connector provides an unbalanced line level output from the Mic/Line/DI preamplifier. Plugging a jack into this connector does not effect the signal path through the MPX10. Source impedance is 100 which is suitable for driving loads of 1k and greater.
COMPRESSOR SECTION I N P U T jack Tip Hot (signal +) Sleeve Screen (signal ground) This is the input to the Compressor section and is normally connected to the 'output' of the Mic/Line/DI preamplifier. Plugging a jack into this connector breaks the signal path and the Tip of the inserted jack becomes the input to the compressor (Half-Normalled). All the 'Input' and 'Output' connectors between each of the processing sections on the MPX10 work in this way.
O U T P U T jack Tip Hot (signal +) Sleeve Screen (signal ground) An unbalanced output from the Compressor section.
EQUALISER SECTION I N P U T jack Tip Hot (signal +) Sleeve Screen (signal ground) Unbalanced input to the EQ section. Half-Normalled to the output of the Compressor section O U T P U T jack Tip Hot (signal +) Sleeve Screen (signal ground) Unbalanced output from the EQ section. OUTPUT SECTION I N P U T jack Tip Hot (signal +) Sleeve Screen (signal ground) Unbalanced input to the Output section. Half-Normalled to the output of the EQ section.
3.0 WARRANTY Your LA Audio MPX10 has been manufactured to a high standard using quality 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 five years 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.
4.0 DESCRIPTION OF CONTROLS 4.1 INPUT SECTION G A I N control This control adjusts the sensitivity of the MPX10's input amplifier. GAIN has different ranges depending on which input is selected - MIC +10dB CCW (counter clockwise) +60dB CW (clockwise) LINE -10dB +20dB CW CCW DI 0dB +30dB CW CCW The LINE 0 mark on the GAIN control gives a unity gain setting for the Line input. C L I P led Lights 3dB before maximum signal level to show transient peaks approaching clipping.
Fig 4.1.1 Input section rear panel showing the Line/DI switch + 4 8 V switch Pressing this switch applies +48V to both pins 2 and 3 of the Microphone input connector. This Phantom Power voltage is commonly used to power capacitor microphones and DI (direct injection) boxes via the input signal cable. To prevent the chance of damage to any external pieces of equipment, do not use the +48V power option with unbalanced input sources ie. those where pins 1 and 3 are connected together.
level falls the more the gain is reduced. Expander response is soft knee around the onset of attenuation which combined with a low ratio (2:1) and slow decay (similar to 'release' on a gate) time ensures transparent operation. The fast recovery (similar to 'attack' on a gate) time ensures that leading transient edges are not lost. N R T H R E S H O L D control Sets the point at which the expander starts to attenuate. Threshold range is 0dB (reference +4dBu), CW to -70dB, fully CCW.
Fig: 4.3.1 Effect of Ratio control on O/P levels. A RATIO of 1:1 gives no compression and 20:1 causes effectively no increase in output level no matter how far the signal increases above Threshold. This is referred to as Limiting. The ratio curves shown in Fig 4.3.1 are Hard-knee where the change in gain is abrupt. The MPX10 has a Soft-knee control system which provides a gradual change between compression levels.
Using FAST attack, the compressor reacts more to signal peaks and will control all but the fastest transients. D S switch Pressing DS introduces a sibilant filter into the sidechain of the compressor. This makes the compressor more sensitive to high frequency 'S' sounds. DS provides 8dB of compression at 8kHz (relative to 1kHz). Please note this is broad-band de-essing and all frequencies are compressed when an 'S' sound is detected.
Maximum cut or boost occurs at the centre frequency set by the FREQUENCY control. Q control Varies the 'Q' (bandwidth) of the cut or boost region. A low Q, CW (clock wise) affects a wide band of frequencies whilst a high Q, CCW affects a very small band. The Q control on the MPX10 has a range of 0.3 (3 octaves) to 12 (1/12th octave) - see the following diagram.
H M F control Sets the amount of cut or boost for the HMF (High Mid Frequency) section. F R E Q U E N C Y control This control varies the cut or boost centre frequency for the HMF section. Control range is 500Hz, CCW to 20kHz, CW. Q control Varies the 'Q' of the cut or boost region for the HMF section. H F control High frequency shelving equaliser. Provides ±15dB cut or boost at 12kHz. 1 2 k H z switch Inserts a 12kHz, -6dB/octave filter into the post EQ signal path.
O U T P U T control The OUTPUT adjusts the final level from the MPX10. It can be used to level match between equipment connected to the MPX10. Adjustment range is -20dB to +20dB. G A I N R E D U C T I O N meter The led meter displays the applied gain reduction (GR) in dBs. In BYPASS the display is dimmed but still displays the amount of gain reduction which would be applied if the compressor were to be switched in. O U T P U T L E V E L meter The led meter displays the overall output level of the MPX10.
5.0 APPLICATIONS Using the MPX10 to record direct to tape, rather than through a mixing console and associated cabling, will result in a cleaner, less cluttered recorded sound which has more definition. 5.1 INPUT The Microphone input is optimised for low impedance microphones (600 types) however the low gain settings available allow plenty of headroom for high output capacitor and condenser mics.
And the RATIO setting of 2:1 ratio means that for every 2dB the input signal increases above the Threshold, the output will increase by only 1dB. By enabling low level signals to be increased without a corresponding increase in the high level signals, a compressor is able to increase the average sound level without risk of high level distortion. This fundamental principle of compression can be used for many applications.
+ Avoid over compression as this may produce a dull sound. It is better to apply gentle compression twice, once during recording which has the benefit of increasing signal headroom and then again on replay/mix down. Vocal de-essing Some microphone/vocalist combinations produce significant 'ess' sounds (sibilance). The MPX10 compressor can be used to reduce these sounds by making the compressor more sensitive to these frequencies. Press in the 'DS' switch on the compressor section.
The technique for reducing mic leakage is similar to the one above. 5.4 EQUALISER The MPX10 offers High and Low shelving equalisers and two fully variable parametric Mid sections. In general the shelving EQs are easy to use and have a smooth, musical character. HF (12kHz) is used to add sparkle and zing to vocals and guitars. The LF control (80Hz) is used to fatten and add warmth to bass sounds.
AUDIO SWEETENING and PRECISION EQUALISATION The following are a few practical examples which should be treated as clues, with personal taste, source sounds and material you are creating deciding the final settings. There are no hard and fast rules, the most important tools in any equalisation process are your ears.
The 75Hz high pass filter is useful for removing subsonics such as wind and stage noise and will help produce a much tighter bass and vocal sound. MAKING A COMPRESSOR FREQUENCY CONSCIOUS Inserting an equaliser such as the Millenium EQX20 (or even the EQ from the MPX10) into the side chain of the compressor will make it more sensitive to certain frequencies. Examples of this technique are De-Essing and De-Popping.
6.0 CIRCUIT DESCRIPTION +48V Gain Mic/Line Mic Clip Phase Filter Output Line DI Line/DI Input Output VCA Control Voltage Sidechain Expander Sidechain DS Filter + + Gain Threshold RMS Detector EXP Compressor Sidechain Threshold Ratio Auto Gain reduction Bypass Input HF HF 2 x Mids Gain Freq Filter LF Q LF Output -10dBV Input Output +4dBu Output Level Fig: 6.0.
6.1 INPUTS The Mic input has a dedicated amplifier stage which is optimised for low noise, impedance matching and common mode rejection. This amplifier is protected against RFI and excessive input levels. The GAIN control for this stage is ganged to the Line amplifier to ensure maximum signal headroom. The +48V phantom power is supplied to pins 2 and 3 of the XLR connector via 6k8 resistors.
COMPRESSOR The Threshold control sets a DC reference level above which compression can start. This is compared to the RMS voltage and when this exceeds the reference the difference is forwarded to the Ratio control. RATIO The difference voltage from the Threshold stage is amplified or attenuated depending on the setting of Ratio. This control voltage defines the amount of compression once Threshold has been exceeded.
ATTACK-RELEASE Attack and Release are based around two time constants. An initially short time which reacts to lower level and/or short duration signals, and a longer time constant for higher levels and/or longer duration. The outputs of the Expander and Compressor sidechains are combined and drive both the VCA control port and the Gain Reduction meter. LINK The LINK connector allows the RMS detectors of two MPX10s to be joined together for stereo operation.
7.0 SPECIFICATIONS INPUTS MIC LINE DI electronically balanced, 1.2k , XLR-F, pin 2 = hot electronically balanced, 20k , 1/4" TRS, Tip = hot unbalanced, 0.5M , 1/4" jack, wired Tip = hot OUTPUTS Type XLR-M 1/4" TRS jack Impedance Max. output Ground sensing, balanced impedance +4dBu, wired pin 2 = hot -10dBV, wired Tip = hot <100 +20dBu PERFORMANCE THD Noise Frequency response < 0.
Weight Unit = 2.2kg, Shipping = 2.85kg LA Audio reserves the right to alter any feature or specification without prior notice E&OE.
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