How it Works
Universal Audio
Loading...
LA-2A
User Guide
21 pgs236.5 Kb0

Universal Audio LA-2A User Guide

Model LA-2A
Leveling Amplifier
Universal Audio, Inc.
www.uaudio.com
PO Box 3818
Santa Cruz, CA 95063-3818
Teletronix LA-2A by Universal Audio
1969. Straightforward in its design, and initially intended for broadcast applications, the LA-2A
quickly became standard equipment in studios worldwide. Many have been painstakingly maintained for the 30 years that they have remained in use since production stopped. A tube-based compressor, the LA-2A features hand-wired components and two simple controls. At the time, its electro-luminescent optical gain reduction was quite revolutio nary: applying the audio signal to an electro-luminescent light panel which shines on a photo­electric cell which in turn controls the gain. In co ntrast to the electro-optical devi ces which preceded it, the electro-luminescent light source provided the fast attack necessary for broadcast applications. Additionally, the cadmium-sulfide photo-cells provided a very natural “two-stage” release which resulted in a compression characteristic more transparent than the other compressors of its day. To this day the LA-2A delivers a trademark sound treasured by engineers worldwide.
Here at Universal Audio, we have gone to great lengths to recreate the LA-2A with complete authenticity. It’s been no small feat to locate obscure parts, put quality control programs in place that didn’t exist 30 years ago and find personnel capable of the handwork that goes into each unit. Every step was necessary to ensure that each LA-2A delivers the sound you expect.
As for the future, we are working on additional reproductions beyond the LA-2A and 1176LN. To that end, we are interested in your opinions about your favorite pieces of vintage gear. What can’t you live without? What would you lo ve to own, but can’t find any longer? In addition, Universal Audio is working on new products designed to meet the demands of the modern digital recording studio, yet retaining the character of classic vintage equipment.
Developing these products has been quite an adventure, enjoyed by all involved. We thank you for your support and we thank my father, Bill Putnam.
Thank you,
Bill Putnam
ii
IMPORTANT SAFETY INSTRUCTIONS
Before using this unit, be sure to carefully read the applicable items of the se operating instructions and t he safety suggestions. Afterwards keep them handy for future reference. Take special care to follow the warnings indicated on the unit its elf, as well as in the operating instructions.
Water and Moisture – Do not use the unit
1.
near any source of water or in excessively moist environments.
Object and Liquid Entry – Care should be
2.
taken so that objects do not fall, and liquids are not spilled, into the enclosure through openings.
Ventilation – When installing the unit in a rack
3.
or any other location, be sure there is adequate ventilation. Improper ventilation will cause overheating, and can damage the unit.
Heat – The unit should be situated away from
4.
heat sources, or other equipment that produces heat.
Power Sources – The unit should be connected
5.
to a power supply only of the type described in the operating instructions, or as marked on the unit.
Power Cord Protection – AC power supply
6.
cords should be routed so that they are not likely to be walked on or pinched by items placed upon or against them. Pay particular attention to c ords at plugs, convenience receptacles, and the point where they exit from the unit. Never take hold of the plug or cord if your hand is wet. Always grasp the plug body when connecting or disconnecting it.
Grounding of the Plug – This unit is
7.
equipped with a 3-wire grounding type plug, a plug having a third (g roundi ng) pin. This plug will only fit into a grounding-type power outlet. This is a safety feature. If you are unable to insert the plug into the outlet, contact your electrician to replace your obsolete outlet. Do not defeat the purpose of the grounding-type plug.
Carts and Stands – The unit should be used
8.
only with a cart or stand that is recommended by the manufacturer. The unit and cart combination should be moved with care. Quick stops, excessive 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 of time.
12.
Damage Requiring Service – The unit
should be serviced by qualified service personnel when:
a) The AC power supply cord or the plug has
been damaged; or Objects have fallen or liquid has been spilled
b)
into the unit; or The unit has been exposed to rain; or
c)
The unit does not operate normally or
d)
exhibits a marked change in performance; or The unit has been dropped, or the enclosure
e)
damaged.
Servicing – The user should not attempt to
13.
service the unit beyond that described in the operating instructions. All other servicing should be referred to qualified service personnel.
iii
LA-2A

User’s Guide
Universal Audio, Inc. PO Box 3818 Santa Cruz, CA 95063-3818 (831) 454-0630 voice (831) 454-0689 fax www.uaudio.com
Universal Audio Part Number LA2A-M01. Revision 1.3
Notice
This manual provides gene ral info rmation, p reparatio n for use, i nstallati on and operat ing instructio ns for t he Universal Audio LA-2A Leveling Amplifier.
The information containe d in this m anual is su bject to change wit hout noti ce. Universal Audio, Inc. makes no warranties of any kind with regard to this manu al, including, but not limited to, the implied warra nties of merchantability and fitness for a particular purpose. Universal Audio, Inc. shall not be liable for errors contained herein or direct, indirect, special, incidental, or consequential damages in connection with the furnishing, performance, or use of this material.
Copyright
2000 Universal Audio, Inc. All rights reserved.
This manual and any associated software, artwork, product designs, and design concepts are subject to copyright protection. No part of this document may be reproduced, in any form, without prior written permission of Universal Audio, Inc.
Trademarks
LA-2A, 1176 and the Universal Audio, Inc. log o are trademarks of Universal Audio, Inc. Other company and product names mentioned herein are trademarks of their respective companies.
iv
Table of Contents
Teletronix LA-2A by Universal Audio...................................................................................ii
Specifications.......................................................................................................................1
Operation of the LA-2A .......................................................................................................2
Input and Output Connections............................................................................... 2
Peak Reduction Control........................................................................................ 2
Gain Control....................................................................................................... 2
VU Meter Operation............................................................................................ 3
Limit / Compress Switch........................................................................................ 3
Calibration...........................................................................................................................4
Meter Zero Adjust ............................................................................................... 4
Side-Chain Pre-Emphasis (R37).............................................................................. 4
Stereo Balance Adjust (R3)................................................................................... 4
Theory of Operation............................................................................................................5
Compressor Basics............................................................................................... 5
Gain Reduction Circuit.......................................................................................... 8
Side-Chain Circuit.............................................................................................. 11
Output Circuit.................................................................................................... 11
Metering Circuit................................................................................................. 11
Appendix.......................................................................................................................... 12
Creative Classics: The 1176 Solid State Limiting Amplifier and the LA-2A
Leveling Amplifier.............................................................................................. 12
The LA-2A..................................................................................................... 12
Developing the 1176..................................................................................... 13
More Than a Vintage Fad: Classic Sound.......................................................... 13
v
Specifications
!
Gain Reduction: up to 40 dB
!
Distortion: less than 0.35% total harmonics at +10 dBm, and less tha n 0.7 5% total harmonics at +16 dBm output
!
Response: +/- 0.1 dB, 30 cycles to 15 kilocycles
!
Noise: 75 dB below +10 dBm output level
!
Gain: 40 +/- 1dB
!
Output Level: +10dBm nominal, +16dBm peaks
!
Input Level: +16 dBm maximum
!
Very fast attack time
!
Release Time: approximately 0.06 seconds for 50% release, 0.5 to 5 seconds for complete release depending upon the amount of previous reduction
!
Input Impedance: 600 ohms balanced
!
Output Impedance: 600 ohms balanced
!
Panel Size: 19” x 5 ¼ ”
!
Depth Behind Panel: 7 ¼”
!
Panel Controls: Gain (Output level), Peak Reduction, and Meter Selector Switch
!
Meter: dB Gain Reduction and dB Output
!
Tube Complement: (2) 12AX7A, (1) 12BH7A, (1) 6AQ5
1
Operation of the LA-2A
Input and Output Connections
Input and Output connections are made using standard XLR style connectors. Terminal strips are also provided.
Output Input
6
7
A-24
12BH7
IEC
Power
Transformer
6AQ5
12AX7
10 9
R3
R37
8
Output connections Input connections
6) Stereo Link 1) + 600 ohms
7) Ground 2) + 250 ohms
8) + 600 ohms 3) Center tap
9) Center tap 4) - 250 ohms
10) - 600 ohms 5) - 600 ohms
Barrier Strip Connections
T4
12AX7
4
5
3
HA-100X
1
2
If you wish to use the barrier strip instead of the XLR connectors, connect as follows: INPUT: Connect + 600 (1) to HOT and –600 (5) to NEUTRAL. OUTPUT: Connect + 600 (8) to HOT and –600 (10) to NEUTRAL.
Connect Ground (7) to the cable shield.
Peak Reduction Control
Operation of the LA-2A is very straightforward. There are only two controls that one must deal with. The first is the Peak Reduction control. This c ontrol should be set so that the compressor exhibits the desired amount of compression. This control should be set independently of the Gain Control.
Gain Control
This control does not affect the compression. The gain control should be set after the desired amount of compression is determined using the Peak Reduction control. Once the Peak Reduction control is set, adjust the Gain Control to achieve the desired output level.
2
Loading...
+ 14 hidden pages
Buy Points How it Works FAQ Contact Us Questions and Suggestions Privacy Policy Cookie Policy Terms of Use