Model 2-LA-2 Twin T4 Leveling Amplifier Universal Audio Part Number 65-00035 Universal Audio, Inc. Customer Service & Tech Support: 1-877-MY-AUDIO Business, Sales & Marketing: 1-866-UAD-1176 www.uaudio.
Notice This manual provides general information, preparation for use, installation and operating instructions for the Universal Audio 2-LA-2 Twin T4 Leveling Amplifier. The information contained in this manual is subject to change without notice. Universal Audio, Inc. makes no warranties of any kind with regard to this manual, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. Universal Audio, Inc.
A Letter From Bill Putnam, Jr. ___________________________________________________________ by Babcock Electronics Corporation. My father, Bill Putnam, Sr., purchased the product rights and the name Teletronix from Babcock Engineering in 1967, folding it into his Studio Electronics Corporation shortly before he changed the name to UREI.
Important Safety Instructions ___________________________________________________________ Before using this unit, be sure to carefully read the applicable items of these operating instructions and the safety suggestions. Afterwards, keep them handy for future reference. Take special care to follow the warnings indicated on the unit, as well as in the operating instructions. 1. Water and Moisture - Do not use the unit near any source of water or in excessively moist environments. 2.
Table of Contents __________________________________________________________ A Letter From Bill Putnam, Jr. ................................................................................................................i Important Safety Instructions ................................................................................................................ii Two Page, Two Minute Guide To Getting Started ....................................................................................2 Front Panel .
The Two Page, Two Minute Guide To Getting Started __________________________________________________________ No one likes to read owner’s manuals. We know that. We also know that you know what you’re doing—why else would you have bought our product? So we’re going to try to make this as easy on you as possible. Hence this two-page spread, which we estimate will take you approximately two minutes to read.
The Two Page, Two Minute Guide To Getting Started __________________________________________________________ Step 5: Power on the 2-LA-2. The purple LED above the power switch will light up. Because the 2-LA-2 is a tube device, it needs several minutes to achieve stable operating temperature. During warm-up, audio quality may vary slightly. Because it can run quite hot, we recommend you power off the 2-LA-2 when it is not being used for extended periods of time. .
Front Panel __________________________________________________________ Figure 1: 2-LA-2 Front Panel NOTE: The 2-LA-2 provides two channels, each of which have identical front panel controls. (1) COMPRESS / LIMIT switch - Determines whether the 2-LA-2 channel is acting as a compressor or a limiter. When set to the down (COMPRESS) position, the degree of compression is gentler and at a low ratio (approximately 4:1,program-dependent).
Front Panel __________________________________________________________ (6) Peak Reduction - Determines the amount of gain reduction provided by the 2-LA-2 channel. This control essentially combines the Threshold, Ratio, and Input controls found on other compressors. Higher settings will increase the relative amount of compression, while lower settings reduce the amount of compression (a setting of 0, with the knob at its fully counterclockwise position, results in no compression).
Rear Panel __________________________________________________________ Figure 2: 2-LA-2 Rear Panel (1) AC Power Connector - Connect a standard, detachable IEC power cable (supplied) here. If fuse replacement is required, use only a 1.6 A time delay (slow blow) fuse for operation at 100 or 120 volts, or an 800 mA time delay (slow blow) fuse for operation at 240 volts.
Interconnections __________________________________________________________ Figure 3: Using the 2-LA-2 as a send-return processor In the above illustration, one side of the 2-LA-2 is used as a send-return processor.
Interconnections __________________________________________________________ Figure 4: using the 2-LA-2 inline with a mic preamp In the above illustration, one side of the 2-LA-2 is used inline with a mic preamp. This is typically done to prevent peaks in the input signal from overdriving the recording device or mixer.
Insider’s Secrets __________________________________________________________ Whatever you can do with an LA-2A, you can do with a 2-LA-2... two times over. In addition, Link mode allows the 2-LA-2 to process not just monophonic signals, but stereo signals such as drum or backing vocal submixes. You can even strap the 2-LA-2 across the master bus, using it as a premastering tool. Vocals, Vocals, Vocals The original LA-2A was often thought of primarily as a vocal compressor.
Insider’s Secrets __________________________________________________________ The LA-2A is also used by many engineers on kick drum. Often, a kick drum does not need a lot of compression, but a compressor can nonetheless tame the big peaks, and add some character and tone to boot. The LA-2A has just the right attack time to let the beater hit come through, then the programdependent nature of the release time gracefully pulls the volume back as the low-end thump occurs.
Insider’s Secrets __________________________________________________________ Versatility You’ll undoubtedly find lots of other uses for your 2-LA-2. In his review, Batzdorf commented on the versatility of the LA-2A, saying, “The thing about [it] that makes it so good in the right application is the way it can control the most unruly signals incredibly tightly and still sound completely natural. “ The LA-2A can control the most No pumping, no compression nasties.
The Technical Stuff __________________________________________________________ History of the 2-LA-2 The original LA-2A design was the brainchild of James F. Lawrence Jr., who had been a radar operator in World War II. Following his tour of duty, Lawrence began studying electrical engineering at the University of Southern California, while also quietly designing sub-miniature telemetry devices and optical sensors for the military.
The Technical Stuff __________________________________________________________ Teletronix LA-2 Engineer Sid Feldman purchased an LA-2 early on, and soon became involved in its distribution, selling units to numerous broadcast and recording facilities in New York and Nashville. In 1962 Lawrence began to reconfigure the LA-2 into the LA-2A, at which time the device gained a Limit/Compress switch in response to the newfound interest from the recording industry.
The Technical Stuff __________________________________________________________ stereo operation, largely because T4 modules often vary slightly between units in their release times. While they are similar enough from unit to unit to independently achieve the famous LA-2A sound, ganging them together can be less than ideal, as these subtle differences in release times can negatively affect the stereo image.
The Technical Stuff __________________________________________________________ Despite the increased dynamic range, compression is especially important when recording digitally, for two reasons: One, it helps ensure that the signal is encoded at the highest possible level, where more bits are being used so that better signal definition is achieved.
The Technical Stuff __________________________________________________________ As you can see from the illustration above, at a low ratio, a compressor has relatively less effect on the incoming signal; at higher ratios, it has more effect.
The Technical Stuff __________________________________________________________ Attack and Release The main key to the sonic imprint of any compressor lies in its attack and release times; these are the parameters which most affect how “tight” or how “open” the sound will be after compression. The attack time describes the amount of time it takes the compressor circuitry to react to and reduce the gain of the incoming signal, usually given in thousandths of a second (milliseconds).
The Technical Stuff __________________________________________________________ Electro-Optical Compression/Limiting In order to operate, a compressor must first have some method of determining the level of the incoming signal, and must then be able to use the fluctuations in that signal to control the gain. There are many different circuit designs which have been developed to accomplish these tasks.
The Technical Stuff __________________________________________________________ The electroluminescent panel utilized in the T4 discharges most of its light very quickly, resulting in an extremely fast attack time (which can be as low as 10 milliseconds, depending on the frequency of the incoming signal), Even more critical to the sound of the 2-LA-2 compressor is its signal-dependent release time.
The Technical Stuff __________________________________________________________ Operating The 2-LA-2 In Link Mode The two T4 gain reduction cells in the 2-LA-2 have been carefully matched to allow smooth and musical operation when stereo linked, with equivalent attack and release times in both channels. When operating the 2-LA-2 in Link mode ( see #7 on page 5), the Peak Reduction knobs in each channel serve to mix the two incoming signals to the side-chain circuit of both channels.
The Technical Stuff __________________________________________________________ Making A Custom Insert Cable In order to ensure unity gain, the input and output to a compressor are normally derived from a channel or bus insert send and return.
The Technical Stuff _______________________________________________________________________ 5. Your finished cable should look like the photograph below. Be sure to check continuity with a voltmeter or test light before use, to ensure proper grounding and signal flow.
The Technical Stuff __________________________________________________________ Maintenance Information Meter Calibration The 2-LA-2 meters may occasionally need to be calibrated. This is accomplished by adjusting the GR Zero Set potentiometer, located to the left of each channel’s Meter switch. The procedure for adjusting the meter is as follows: 1. Power on the 2-LA-2 and allow it to warm up for five minutes. 2. Set the Meter switch for the channel being calibrated to its up (GR) position. 3.
The Technical Stuff _______________________________________________________________________ NOTE: When changing operating voltage, the fuse value must be changed as well. Make sure the 2-LA-2 is properly set for the voltage in your area before applying AC power to the unit! Failure to do so may damage the unit. Changing Fuses The AC power fuse is located in the AC power connector block. Remove the power cord before checking or changing the fuse. A 1.
The Technical Stuff __________________________________________________________ Block Diagram As shown in the illustration above, each channel’s input transformer provides isolation and impedance matching. After this, the signal is fed into both the side-chain circuit and the gain reduction circuit. The side-chain is comprised of a voltage amplifier, a pre-emphasis filter, and a driver stage which provides the voltage necessary to drive the electro-luminescent panel.
Glossary Of Terms __________________________________________________________ Ambient noise floor - Low-level noise created by environmental factors such as fans, air conditioners, heaters, wind noise, etc. Attack time - Describes the amount of time it takes compressor circuitry to react to and reduce the gain of incoming signal. A compressor set to a fast attack time kicks in almost immediately and catches transient signals of very brief duration, reducing their level and thus "softening" the sound.
Glossary Of Terms __________________________________________________________ Ducking - No, nothing to do with Donald. Describes the technique of using the level of one signal to control the level of another. In broadcast applications, a music bed is often automatically “ducked” whenever the announcer’s voice is heard; it then returns to its original level when the announcer stops speaking. Dynamic range - The difference between the loudest sections of a piece of music and the softest ones.
Glossary Of Terms __________________________________________________________ Millisecond (ms) - A thousandth of a second. Patch bay - A passive, central routing station for audio signals. In most recording studios, the line-level inputs and outputs of all devices are connected to a patch bay, making it an easy matter to re-route signal with the use of patch cords. Patch cord - A short audio cable with connectors on each end, typically used to interconnect components wired to a patch bay.
Recall Sheet __________________________________________________________ - 29 -
Specifications _______________________________________________________________________ Output Level +20 dBu nominal, @ 1% Input Level +24 dBu maximum Output Impedance 600 Ω balanced Input Impedance 600 Ω balanced Maximum Gain 35 dB +/- 1 dB Frequency Response 30 Hz to 15 kHz +0.
Additional Resources/Product Registration/Warranty/Service & Support __________________________________________________________ Additional Resources We’ve got a pretty cool website, if we may say so ourselves. Check us out at http://www.uaudio.com.
