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Model LA-3A

AUDIO LEVELER

Universal Audio Manual Number 65-1301

Revision 1.53

Summary of Contents for LA-3A

Page 1: ...Model LA 3A AUDIO LEVELER Universal Audio Manual Number 65 1301 Revision 1 53 ...

Page 2: ...e force and uneven surfaces may cause the unit and cart combination to overturn 9 Wall Or Ceiling Mount The unit should be mounted to a wall or ceiling only as recommended by the manufacturer 10 Cleaning The unit should be cleaned only as recommended by the manufacturer 11 Nonuse Periods The AC power supply cord of the unit should be unplugged from the AC outlet when left unused for a long period ...

Page 3: ... cadmium sulfide photocells provided a very natural two stage release which resulted in a compression characteristic more transparent than the other compressors of the day The LA 3A features hand wired components and two simple front panel controls Its ease of operation and signature tone make it a first call for vocals guitars and just about any application where an ultra fast release time is not...

Page 4: ...Contour Control 6 Input Output XLRs 6 AC Power 6 Fuse Mains 6 Voltage Select 6 Unbalanced Connections 7 Balanced Connections 7 Chassis Ground 7 STEREO OPERATION 7 Rear Chassis Link Connections 7 Stereo Setup Calibration 8 Stereo Use 8 Applications 8 Control Settings 8 WHAT COMPRESSORS DO 9 Attack and Release 9 Compressing Vocals 10 Bass Guitar 10 Any Sound 10 Tricks 10 RACK MOUNTING 10 Single Unit...

Page 5: ...2 COMPRESSOR THEORY OF OPERATION 12 Compressor Basics 12 The T4 Cell 14 Side Chain Circuit 15 HISTORICAL NOTES 16 The 610 Preamp 17 Classic Compressors 17 The 1176 LN 17 The LA 2A 18 RECALL SHEET 19 ...

Page 6: ...r 80 dB limiting threshold Distortion 0 35 THD 24 dBm Max Gain Reduction 40 dB Attack Time 1 5ms or less program dependent Release Time stage 1 60 ms 50 release Release Time stage 2 0 5 to 5 seconds program dependent General Power Requirements 115V 230V operation Fuse 115V use 3AG 1 8amp TD slow blow Fuse 230V use 3AG 1 16 amp TD slow blow Max Power Consumption 35 Watts Dimensions 3 5 vertical 2RU...

Page 7: ...witch below the GAIN knob should be set to GR to view the amount of gain reduction the LA 3A is doing We recommend adjusting the PEAK REDUCTION control until the meter reads between 3 and 5 on the meter during volume peaks NOTE adjusting the level of the device that s plugged into the LA 3A input as well as adjusting the PEAK REDUCTION control knob can affect the amount of compression Heavily comp...

Page 8: ...ront panel drawing on page 3 1 Turn the LA 3A on and warm up for 5 minutes 2 Set the meter switch to the GR position 3 With the PEAK REDUCTION control full off CCW adjust the GR zero set trim pot so the meter reads 0 dB Turn pot slowly LA 3A REAR CHASSIS SERIAL MODEL On the left AC Power transformer FUSE holder 115V 230V switch and standard IEC AC power recep tacle In the middle LIMIT COMPRESS swi...

Page 9: ...ation on page 6 for more info High Frequency Contour Control The HF CONTOUR control is a high frequency boost of the signal feeding the gain reduction circuit This control is NOT an EQ of the audible program material It s function is to make the compressor more sensitive to high and high mid frequency content and to compress or attenuate that spectrum more than the mid and low end frequencies that...

Page 10: ...ls AND the Output XLR jack Unbalanced Connections Connect the hot cable lead usually pin 2 of XLR cable to the terminal Connect the shield braid to the COM terminal Balanced Connections Connect the hot cable lead usually pin 2 of XLR cable to the terminal Connect the neutral lead usu ally pin 3 of XLR cable to the COM terminal Chassis Ground Connect the ground or shield braid usually pin 1 of XLR ...

Page 11: ... the stereo signal equally regardless of which side left or right is triggering the gain reduction Applications This manual section is for those who haven t had a lot of experience using compressors If the LA 3A is your first compressor then this section may be particularly helpful The Compressor Theory of Operation on page 11 is a more technical overview of compressors and how the electronic circ...

Page 12: ...ntrol is set to a fast setting the compressor will instantly turn the signal down which will attenuate the high frequency transients that are present in the initial attack This is a good way to warm up an overly bright or edgy acoustic guitar recording If the attack control is set to a slow set ting the natural full volume of the sounds attack will be heard and then the slow acting compressor will...

Page 13: ...ment Tricks Try connecting two compressors together in series Try using an 1176 or other compressor set for fast attack and release in front of an LA 3A Try it the other way around with the LA 3A going into the other compressor Split a signal send one to the LA 3A and compress it medium to deep 5 to 10 mix this with the natural un compressed signal Try different levels of the mix try using just a ...

Page 14: ...the 4 screws that were removed from the top cover DO NOT tighten the screws yet 4 Slip the second LA 3A under the STRAPPING PLATE on the left LA 3A Connect the two LA 3As together by re inserting the 4 screws that were removed from the second unit top cover 5 Tighten up all screws while checking the alignment of the Units DO NOT cinch too tight 6 Carefully flip the units over on to their tops Repe...

Page 15: ... specified range an amplifier provides a constant amount of gain regardless of the level of the input signal In figure 4 below the middle line depicts a perfect amplifier with a gain of 10 dB To see this notice that a signal with an input level of 30 dB will result in an output level of 20 dB which is an increase of 10 dB Similarly an input level of 0 dB will result in an output level of 10 dB hen...

Page 16: ...e output signal thus expanding the dynamic range As mentioned previously the compression ratio is defined as the ratio of the increase of the level of the input signal to the increase in the level of the output signal In this example the input level is increased by 10 dB while the output level only increases 5 dB This would be a compression ratio of 2 1 Lower ratios such as 2 1 result in more gent...

Page 17: ...ded and there would be no output In reality the photocell resistance cannot go completely to zero and hence there will always be some signal present The T4 electro optical device is the heart of the compressor and its gain reduction characteristics Its unique characteristics affect the overall sound and character of the LA 3A In addition to the compression curve the combination of the EL panel and...

Page 18: ...entiometer This potentiometer controls the gain of the side chain circuit The greater the gain of this circuit the lower the threshold and the greater the amount of compression will be The term side chain comes from the process of splitting the audio into a side path to be used for sensing and controlling loud volume peaks The LA 3A is a feedback style compressor This is due to the fact that the s...

Page 19: ...UREI built products that are still in regular use decades after their development In 1999 Bill Jr and James Putnam re launched Universal Audio and merged with Kind of Loud technologies a leading audio software company with two goals Reproduce classic analog recording equipment designed by their father and his colleagues research and design new recording tools in the spirit of vintage analog techno...

Page 20: ...r his efforts and his contribution to our efforts to trace the history of the 610 At least one 610 module is still in use at Ocean Way Allen Sides who purchased the studio from Putnam to open Ocean Way personally traveled to Hawaii to collect the 610 console that was used to record the live Ha waii Calls broadcasts Jack Joseph Puig has been ensconced in Studio A with the 610 and a stunning collec ...

Page 21: ...l additional sets of windings to provide feedback which makes it an integral component in the operation of the output amplifier Putnam spent a great deal of time perfecting the design of this tricky transformer and carefully qualified the few vendors capable of produc ing it The first major modification to the 1176 circuit was designed by Brad Plunkett in an effort to reduce noise hence the birth ...

Page 22: ... fax 831 466 3775 GR OUTPUT POWER ON UNIVERSAL AUDIO INC SANTA CRUZ CALIFORNIA GR OUTPUT POWER ON UNIVERSAL AUDIO INC SANTA CRUZ CALIFORNIA GR OUTPUT POWER ON GAIN PEAK REDUCTION UNIVERSAL AUDIO INC SANTA CRUZ CALIFORNIA GR OUTPUT POWER ON GAIN PEAK REDUCTION UNIVERSAL AUDIO INC SANTA CRUZ CALIFORNIA ...

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