CX335 Technical Manual Cloud Electronics Limited 140 Staniforth Road, Sheffield, S9 3HF England Tel + 44 (0) 114 244 7051 Fax + 44 (0) 114 242 5462 e-mail info@cloud.co.uk web site http://www.cloud.co.
CX335 Technical Manual Page 1 CX335 STEREO COMPRESSOR LIMITER OPERATION and SERVICE GUIDE CONTENTS SECTION 1 "...where angels fear to tread" Soft Knee, Fast Time Constants Hard Knee, Fast Time Constants Intelligent Limiting Soft Knee, Slow Time Constants Hard Knee, Slow Time Constants SECTION 2 Introduction SECTION 3 Installation Mounting Audio connections Power connection see page 3 section 1.01 section 1.02 section 1.03 section 1.04 section 1.05 see page 7 see page 8 section 3.01 section 3.
Page 2 CX335 Technical Manual SECTION 9 Audio Calibration STATIC TESTING Initialise Control settings Operating D.C. Voltages VU meters Set 0dB level Set Total Harmonic Distortion (THD) Peak Control Compression Laws Re-check levels DYNAMIC OBSERVATIONS Test tone sequences Dynamic Control settings Program dependant waveforms (Hard compressor) Program dependant waveforms (Slow compressor) Program dependant waveforms (Soft compressor) Program dependant waveforms (Peak limiter) section 9.09 section 9.
CX335 Technical Manual 1 Page 3 "... where angels fear to tread." OK. It's 6.30pm, and the unit has just been delivered, and the Club opens tonight! Rather than read the whole manual you can take this short-cut route, but be it on your own head. Connect the unit into the signal path directly after the system mixing desk or DJ console, and just before any amplifiers or cross-over.
Page 4 CX335 Technical Manual With normal programme level running through the CX335, rotate the Gain control so that the output level on the Left and Right channel VU meters measures about the same in Bypass mode as it does with the Compressor operational. Then rotate the Peak Limiter control to a position where the peak LED only flashes occasionally to capture very high level peaks for speaker protection.
CX335 Technical Manual Page 5 SET TO CAPTURE VERY HIGH PEAK TRANSIENTS ROTATE TO DESIRED LIMIT LEVEL RELEASE KNEE HARD 3 2 -15 5 +10 SLOW -10 10 5 1.5 1.2 -20 -2 -4 20 4 4 8 8 26 -6 12 dB 12 PEAK RATIO THRESHOLD 0 15 6 10 3 20 0 8 0dB MAKE EQUAL TO BYPASS LEVEL BYPASS GAIN LIMITING ABOVE 20:1 have a definite maximum output level that will never be exceeded (many LEDS lit on the Gain Reduction meter).
Page 6 CX335 Technical Manual ROTATE UNTIL LED FLASHES AT DESIRED PEAK OUTPUT ROTATE UNTIL -8 TO -12dB BELOW SIGNAL INPUT RELEASE KNEE HARD 3 2 -15 5 +10 SLOW -10 -20 THRESHOLD 10 5 1.5 1.2 RATIO COMPRESSING BELOW 10:1 -2 -4 0 15 6 10 3 20 0 8 0dB 20 26 -6 PEAK MAKE EQUAL TO BYPASS LEVEL 4 4 8 8 12 dB 12 GAIN BYPASS LIMITING ABOVE 20:1 Depress the Hard and Soft switches. Set the Threshold to somewhere between 5dB and 8dB LOWER than your maximum input level.
CX335 Technical Manual Page 7 Introduction The Cloud CX335 Stereo Compressor Limiter has been designed to provide all the functional needs of the system installation engineer with a desire to perform signal levelling and overload protection. The unit can be applied equally to any discotheque or live installation as well as in the recording studio and mastering facility.
Page 8 CX335 Technical Manual Installation 3.01 Mounting The CX335 is designed for standard 19" rack mounting and occupies 1U of rack space. Avoid mounting the unit directly above power amplifiers or power supplies that radiate significant amounts of heat and strong magnetic fields. Fibre or plastic washers may be used to prevent the front panel becoming marked by the mounting bolts. 3.
CX335 Technical Manual Page 9 VOLTS OPERATION FIT TWO LINKS FOR 110/120 TRANSFORMER 120V TRANSFORMER HIGH VOLTAGE VOLTS OPERATION HIGH VOLTAGE FIT ONE LINK FOR 220/240 240V 120V VIEW INSIDE CX335 SHOWING POSITION OF VOLTAGE SELECTION LINKS COMPRESSORS and LIMITERS 4.01 What is a compressor / limiter? Compression is an audio process that reduces the output progressively once the input level has risen above a pre-settable threshold.
Page 10 CX335 Technical Manual INPUT IN dBs GRAPH OF INPUT LEVEL VERSES OUTPUT LEVEL NO COMPESSION +10 +5 HARD KNEE 0dB RATIO 10:1 OR LESS -5 -10 SOFT KNEE THRESHOLD LIMITING -15 RATIO 20:1 OR GREATER -20 -25 -30 OUTPUT IN dBs -30 4.04 -25 -20 -15 -10 -5 0dB +5 +10 Ratio explained. For a hard-knee compressor, the effect of Ratio can be easily understood by remembering that ratio is a comparison between input levels and output levels.
CX335 Technical Manual 4.07 Page 11 Understanding Compressor Limiters verses Peak limiting Due to the range of the ratio control, the compressor can be set up to perform as a very effective limiter. Further-more, with its soft knee operation, the characteristics of the unit blend from gentle compression for signal just above threshold, through to hard limiting. The intelligent control circuitry and programme dependent attack and release make the audible effect almost un-noticeable.
Page 12 CX335 Technical Manual RELEASE KNEE 5.04 HARD 2 -15 5 +10 SLOW -10 -20 THRESHOLD 3 10 5 1.5 1.2 RATIO -2 -4 0 15 6 10 3 20 0 8 0dB 20 26 -6 PEAK 4 4 8 8 12 dB GAIN 12 BYPASS Ratio: With the Hard switch depressed, this control governs by how much the input level must rise before a rise of 1dB would be seen at the output.
CX335 Technical Manual Page 13 OUTPUT DISPLAY GAIN REDUCTION 30 20 15 10 6 4 2 L 1 0dB -20 -16 -12 -8 -4 0dB +4 +8 +12 R 5.08 Gain Reduction Meter: A nine segment LED bargraph meter continuously monitors the gain reduction applied by the compressor and or limiter and even any remote control voltage over the range 0 to 30dB. The amount of gain reduction shown is greatly affected by all of the front panel controls.
Page 14 CX335 Technical Manual Operation The unit should be connected in line with the stereo signals to be processed either by breaking the existing connection between mixer console and cross-over or amplifiers or via suitable insert points on the master outputs of the console, (if such exist). Setting up the front panel controls is easiest if the Peak Limiter threshold is initially set to maximum. This allows the compressor to be set up in isolation.
CX335 Technical Manual Page 15 Circuit Description For clarity the internal circuitry of the CX335 is best described in sections. Both left and right audio inputs are passed through a Voltage Controlled Amplifier (VCA) to the balanced output sections; a signal level detector below 200Hz; a signal level detector above 200Hz ; peak limiter detector; display circuits 7.01 The Audio Path Due to the fact that both Left and Right channels are basically identical, only one channel is described here.
Page 16 CX335 Technical Manual The term 'programme dependant' means that when a large, fast transient occurs the circuits charge and discharge more rapidly. The two LPF and HPF control voltages are Or'd with the output from the limiter and the output from the remote control sensor circuit to produce a common control line IC14a.
CX335 Technical Manual Page 17 Removal of the smaller display Printed Circuit Board should only be necessary if there is a display fault. Viewing the unit from above, remove the 2 M3 machine screws to free the display board from the supporting pillars. Take care not to strain the jumper cable. Audio Calibration Internal adjustments of the CX335 will not need any attention. However if component changes have been made, it may be necessary to adjust one or more of the pre-set potentiometers.
Page 18 CX335 Technical Manual 9.05 THD (Total harmonic distortion, Presets marked PR1 for the left channel and PR3 for the right channel). No adjustment should be made to the THD presets without the use of an accurate THD meter. Correct adjustment will leave the preset approximately central about its track. A level of 0.015% distortion or lower can be expected (especially if the bottom panel is still attached to the unit). 9.06 Apply +20dB input level.
CX335 Technical Manual Page 19 9.08 Re-check the 0dB level as per test number 9.04 for both channels. If there is a large discrepancy, then the calibrations described in 9.07 will need to be re-run. Dynamic Observation - where the oscilloscope displays are subjective. 9.09 For the dynamic observations listed in section 9.09 and onwards, you will need test signal bursts or 'sequences' set to three different levels, and available at two different frequencies.
Page 20 Fig 9.01 CX335 Technical Manual Fig 9.02 9.13 Release the Hard and Slow switches, ensure that envelope changes in level, and that the time constants are slightly different from that in section 9.14 Check the program dependant attack of the Peak Limiter with controls as above, (both Hard and Slow switches released) and gradually decreasing the Limit level to observe the output shown in fig 9.04, (this being extremely dependant on the output Gain setting). Fig 9.03 Fig 9.
CX335 Technical Manual Page 21 TECHNICAL SPECIFICATIONS (All measurements referenced to 0dBu operating level) 10kΩ +26dBu 80 Ω +26dBu 600Ω 20Hz to 20kHz ±0.5dB <-70dB 10kHz INPUT IMPEDANCE MAXIMUM INPUT LEVEL OUTPUT IMPEDANCE MAXIMUM OUTPUT LEVEL MINIMUM OUTPUT LOAD FREQUENCY RESPONSE CROSSTALK NOISE AT UNITY GAIN 22Hz - 22KHz -90dB CCIR ARM -90dB IEC A -92dB DISTORTION (THD and NOISE) Unity Gain, 0dBu +10dBu input 10db Gain Red POWER REQUIREMENTS FUSE RATING FUSE TYPE CASE SIZE WEIGHT 100Hz <0.
