Model 1176LN Solid-State Limiting Amplifier Universal Audio Part Number 65-00046 Universal Audio, Inc. Customer Service & Tech Support: 1-877-MY-UAUDIO 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 1176LN. 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. _____________________________________________________________ Thank you for purchasing the 1176LN Solid-State Limiting Amplifier. My father designed the original 1176 back in 1966, and he was very pleased with his accomplishment. He was also very gratified by its reception by his peers in both the recording and broadcast industries. As a recording engineer, the 1176 was a device he himself used extensively.
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 _____________________________________________________________ 3 A Letter From Bill Putnam, Jr. ................................................................................................................ 3 4 Important Safety Instructions ................................................................................................................ 4 6 Two Page, Two Minute Guide To Getting Started ....................................................................................
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 4: On the right side of the front panel, depress the +4 Meter button. This not only turns on the power to the 1176 but also ensures that the meter displays the final output level. (NOTE: Depressing any Meter button other than OFF also has the effect of powering on the 1176LN; when powered on, the front panel meter lights up.
Front Panel _____________________________________________________________ 1 2 3 4 5 6 7 (1) Input - Determines the level of the signal entering the 1176LN, as well as the threshold. Higher settings will therefore result in increased amounts of limiting or compression. (2) Output - Determines the final output level of signal leaving the 1176LN.
Front Panel _____________________________________________________________ (5) Ratio - These four buttons determine the severity of the applied gain reduction. (A ratio of 4:1, for example, means that whenever there is an increase of up to 4 decibels in the loudness of the input signal, there will only be a 1 dB increase in output level, while a ratio of 8:1 means that any time there is an increase of up to 8 dB in the input signal, there will still only be a 1 dB increase in output level.
Front Panel _____________________________________________________________ (6) Meter - A standard VU meter that displays either the amount of gain reduction, or output level, depending upon the setting of the Meter Function switch. ( see #7 below) Occasionally, the meter may require calibration.
Rear Panel _____________________________________________________________ 3 2 4 1176 SA 1 5 (1) AC Power Connector / Fuse Holder - Connect a standard, detachable IEC power cable (supplied) here. If fuse replacement is required, use only a 125 mA time delay (slow blow) fuse for operation at 115 V, or a 63 mA time delay (slow blow) fuse for operation at 230 V.
Interconnections _____________________________________________________________ 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 1176 SA For most applications, we recommend starting with the 1176LN INPUT and OUTPUT knobs set to approximately 24 (their 12 o’clock position) for unity gain.
Insider’s Secrets _____________________________________________________________ Vocals, Vocals, Vocals The 1176LN has long been considered the preeminent tool “For vocals there really isn’t for recording vocals. Veteran engineer Andy Johns (Led a better compressor” — Zeppelin, Rolling Stones) says flatly, “For vocals there really engineer Andy Johns isn’t a better compressor.” Bruce Swedien is another legendary engineer who is a die-hard 1176 fan. “I love them on vocals,” he says.
Insider’s Secrets _____________________________________________________________ Drums In the world of recording, there’s probably no greater challenge than getting powerful and precise drum sounds. The 1176LN has long been the compressor of choice for engineers for kick drum, snare drum, and overhead or ambient mics.
Insider’s Secrets _____________________________________________________________ The 1176LN compression or limiting is, to some degree, program-dependent. That’s an important feature which allows it to be used in a musical, percussive way. Let’s say you have a medium tempo, 4/4 rock beat—an excellent scenario for using “All-Button” mode. In this application, you’d probably have a lot of input level, a slowish attack (so that the transients sneak through), and a quick release.
Insider’s Secrets _____________________________________________________________ Controlled Distortion The unique sonic characteristics of the 1176LN make it an effective tone shaper as well. One of its features is ultra-fast attack and release times, and used correctly (or incorrectly, depending on the way you look at it), you can use it to add distortion to any otherwise pristine audio track.
The Technical Stuff _____________________________________________________________ History of the 1176LN The original Universal Audio 1176, designed by Bill Putnam, was a major breakthrough in limiter technology – the first true peak limiter with all transistor circuitry offering superior performance and a signature sound.
The Technical Stuff _____________________________________________________________ Revision E was introduced in the early 1970s and was the first to accommodate European 220V mains power with a voltage selector on the rear panel. Of all the revisions, model D and model E are considered to have superior sound and are thus the most sought-after versions by audio engineers. Another significant redesign occurred in 1973.
The Technical Stuff _____________________________________________________________ Compressor / Limiter Basics The function of a compressor is to automatically reduce the level of peaks in an audio signal so that the overall dynamic range—that is, the difference between the loudest sections and the softest ones—is reduced, or compressed, thus making it easier to hear every nuance of the music.
The Technical Stuff _____________________________________________________________ Input Signal and Threshold The first and perhaps most significant factor in compression is the level of the input signal. Large (loud) input signals result in more gain reduction, while smaller (softer) input signals result in less gain reduction. Threshold is another important factor. It is a term used to describe the level at which a compressor starts to work.
The Technical Stuff _____________________________________________________________ maximum value. At very high ratios of 20:1 or greater (some limiters even offer a theoretical infinite ratio of Infinity:1), “brick wall” limiting kicks in—that is, almost any change in input, no matter how great, results in virtually no increase in output level. Note that the 1176LN has been designed so that selecting higher ratios also raises the threshold level.
The Technical Stuff _____________________________________________________________ Output (Makeup Gain) Finally, an output control is employed to make up for the gain reduction applied by the gain reduction circuitry; on the 1176LN, this is the function of the Output knob.
The Technical Stuff _____________________________________________________________ To make such a cable, first acquire the following components: (1) Female XLR cable connector (1) Male XLR cable connector (1) 1/4" TRS cable connector A suitable length of light gauge unbalanced microphone cable A short piece of 22 gauge bus wire Then follow these steps to assemble the cable: 1. Cut two lengths of audio cable suitable to reach from the 1176LN to the insert point on your mixer.
The Technical Stuff _____________________________________________________________ Terminal Strip Connections Because it predated standard XLR connectors, the original 1176LN provided terminal strips for input and output line-level connections, and so that feature has been retained here (in addition to providing a modern XLR input and output).
The Technical Stuff _____________________________________________________________ Maintenance Information Calibrations There are no user serviceable parts inside the 1176LN. Unit calibration, as well as repair, should only be performed only by qualified service personnel. These calibration procedures are provided only for use by qualified service technicians. Zero Set The 1176LN meter may occasionally need to be calibrated.
The Technical Stuff _____________________________________________________________ “Q” Bias The compression threshold is set using R59. Under normal circumstances, this control does not need to be adjusted. The threshold is dependent upon the specific characteristics of the VVR FET (Q1), and it will be necessary to re-adjust it if Q1 is changed. The following procedure is used to set “Q” bias: 1. Select either +4 or +8 output metering. 2. Adjust R59 fully counterclockwise (CCW). 3.
The Technical Stuff _____________________________________________________________ Stereo Operation and Calibration With the use of an external 1176 Stereo Adapter (1176SA), available from Universal Audio, two 1176LNs can be connected for stereo operation. When used in stereo operation, the Attack and Release controls on the two 1176LNs will interact so that changing the Attack or Release times on either device changes that of both devices.
The Technical Stuff _____________________________________________________________ Changing the Voltage Selector The 1176LN can operate at 115V or 230V. It will be factory preset for the voltage in your area; however, if it is necessary to change the voltage selector (located directly below the transformer on the rear panel), use a small slotted screwdriver to slide it to the desired operating voltage. NOTE: When changing operating voltage, the fuse value must be changed as well.
The Technical Stuff _____________________________________________________________ 1176LN Circuit Details The fundamental problem facing Bill Putnam Sr. when he began designing the 1176 limiter was how to keep its FET operating within its linear region in order to keep distortion sufficiently low.
The Technical Stuff _____________________________________________________________ Input Section Figure 2 - Input Section As shown in Figure 2, the 1176LN input section is comprised of an adjustable passive attenuator followed by a transformer. The purpose of this section is to reduce the signal level so as not to overdrive the FET based gain reduction stage. Additionally, the adjustable input level is used to control the amount of compression. This input circuit was used in Revisions A-F.
The Technical Stuff _____________________________________________________________ As shown in Figure 3, gain reduction is achieved by a Field Effect Transistor (FET) which is used as a variable resistor. In the 1176LN, the FET acts like a resistor whose resistance is controlled by the voltage applied to its gate. The higher the voltage applied to the gate, the smaller the drain-source resistance will be. Figure 4 - Using an FET as a voltage-variable resistor.
The Technical Stuff _____________________________________________________________ Output Amplifier The output amplifier is a Darlington pair followed by a class A stage based on a 2N3053 transistor. The 1176LN output stage was essentially the same as the Universal Audio 1108 pre-amplifier. The output transformer is a custom transformer designed by Bill Putnam Sr. Aside from offering output impedance matching, the transformer forms an integral part of the feedback network used to stabilize the output stage.
The Technical Stuff _____________________________________________________________ As shown in Figure 5, this circuit controls the amount of compression as well as the attack and release times of the limiter. The input to this circuit is taken from the output of the preamplifier section, just before the volume control potentiometer (R23). The compression ratio push-button switches determine the level of the signal which is sent to the sidechain. This determines the amount of limiting or compression.
Glossary of Terms _____________________________________________________________ Ambient noise - 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 _______________________________________________________________________ dBm - Short for “decibels as referenced to milliwatt,” dissipated in a standard load of 600 ohms. 1 dBm into 600 ohms results in 0.775 volts RMS. dBV - Short for “decibels as referenced to voltage,” without regard for impedance; thus, one volt equals one dBV. Dynamic range - The difference between the loudest sections of a piece of music and the softest ones.
Glossary of Terms _____________________________________________________________ Patch cord - A short audio cable with connectors on each end, typically used to interconnect components wired to a patch bay. Peak reduction - A synonym for compression or limiting. Program dependent - Refers to a parameter that varies according to the characteristics of the incoming signal. To some degree, the amount of 1176LN gain reduction is program dependent.
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Specifications _____________________________________________________________ Input Impedance 600 Ω, bridged T-control (floating) Output Load Impedance 600 Ω (floating) Frequency Response 20 Hz to 20 kHz ± 1 dB Gain 45 dB, ± 1 dB Distortion > 0.5% T.H.D. from 50 Hz – 15 kHz with limiting, at 1.1 seconds release setting. Output of +22 dBm with no greater than 0.5% T.H.D.
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.
