Model 2-1176 Dual 1176LN Limiting Amplifier Universal Audio Part Number 65-00047 Universal Audio, Inc. Customer Service & Tech Support: 1-877-MY-AUDIO Business, Sales & Marketing: 1-866-440-1176 www.uaudio.
Notice This manual provides general information, preparation for use, installation and operating instructions for the Universal Audio 2-1176. 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 2-1176 Dual 1176LN Limiting Amplifier. My father designed the original 1176 back in 1966, and he was very pleased with his accomplishment. He was equally 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 __________________________________________________________ A Letter From Bill Putnam, Jr. ................................................................................................................ii Important Safety Instructions ................................................................................................................iii 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 7: Set the Attack and Release knobs for both channels fully counterclockwise (to their SLOW position). Step 8: Set the Ratio knobs for both channels to their 4 position, thus selecting moderate compression (at a 4:1 ratio) for both channels. Step 9: Power on the 2-1176. The purple LED above the power switch will light up.
Front Panel __________________________________________________________ NOTE: The 2-1176 provides two channels, each of which have identical front panel controls. (1) Attack - Sets the amount of time it takes the 2-1176 channel to respond to an incoming signal and begin gain reduction. The 2-1176 attack time is adjustable from 20 microseconds to 800 microseconds (both extremely fast).
Front Panel __________________________________________________________ When operating the 2-1176 in LINK mode, the left channel’s Attack and Release knobs affect both channels and the right channel’s Attack and Release controls become nonfunctional. ( For more information, see page 20.) (4) Meter - A standard VU meter that displays either the amount of gain reduction or output level for the channel, depending upon the setting of the Meter Function switch.
Front Panel __________________________________________________________ Engineers typically use the ALL Ratio on drums or on ambience or room mics. It can also be used to “dirty” up a bass or guitar sound, or for putting vocals “in your face.” ( see page 20 for more information) When a Ratio of ALL is selected, distortion increases radically due to a lag time on the attack of initial transients and there are constant changes in the attack and release times, as well as a change in the bias points.
Rear Panel __________________________________________________________ NOTE: The 2-1176 provides two channels, each of which have identical rear panel controls. (1) Line INPUT - Connect line-level input signal for each channel to these balanced XLR connectors. Pin 2 is wired positive (hot). This signal will normally be arriving via a patchbay from a channel or bus insert send. (2) Line OUTPUT - Balanced XLR connectors carrying the line-level output signal of each 2-1176 channel.
Interconnections __________________________________________________________ -8-
Insider’s Secrets __________________________________________________________ Whatever you can do with an 1176LN, you can do with a 2-1176... two times over. In addition, Link mode allows the 2-1176 to process not just monophonic signals, but stereo signals such as drum or backing vocal submixes. You can even strap the 2-1176 across the stereo bus, using it as a premastering tool.
Insider’s Secrets __________________________________________________________ Jim Scott, who won a Grammy for Best Engineered Album for Tom Petty’s Wildflowers, adds, “I use 1176s real conservatively and they still do amazing things. I always use them on vocals.... I’m always on the 4:1 [ratio], and the Dr. Pepper [Attack/Release settings]—you know, 10 o’clock, 2 o’clock, and it does everything I need... They have an equalizer kind of effect, adding a coloration that’s bright and clear.
Insider’s Secrets __________________________________________________________ “When I am mixing,” Johns adds, “I mult the bass drum and the snare. The bass drum will not be even, so the first bass drum track—the one that doesn’t have the 1176 on it—gets to breathe. Then I put another bass drum next to it with an 1176 at a 4:1 [ratio setting]. That evens it out a bit. I sneak that in and the bass drum is more constant. Of course, you have to change your EQs appropriately...
Insider’s Secrets __________________________________________________________ “Treating some electric guitar sounds that had been previously recorded,” Curwin added, “allowed the opportunity of experimenting with the different ratios and the attack and release controls, and with careful positioning it was possible to give the guitar a lot of punch and an apparent sense of urgency in the mix.” Reviewer Michael Cooper tried using the 2-1176 on a rock tune to record electric rhythm guitar, selecting All ratio.
Insider’s Secrets __________________________________________________________ Controlled Distortion The unique sonic characteristics of the 2-1176 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.
Insider’s Secrets __________________________________________________________ mode. Adding a bit of slam-compressed audio to the mix produced a brighter mix without highfrequency overload. It also really helped both drums and guitars maintain a strong place in the mix without overwhelming vocals and bass. For even more control, I also hooked up the 2-1176 as an aux send ‘effect,’ again in All Button mode.
The Technical Stuff __________________________________________________________ History of the 1176 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. Evolved from the popular Universal Audio 175 and 176 vacuum tube limiters, the 1176 retained the proven qualities of these industry leaders, and set the standard for all limiters to follow.
The Technical Stuff __________________________________________________________ Another significant redesign occurred in 1973. The revision F output stage was modified to provide higher output current capability by using a push-pull circuit design borrowed from Universal Audio's new 1109 preamplifier. This new output stage replaced the original Class A circuit borrowed from the 1108 preamp. The meter drive circuit was also updated, with an operational amplifier instead of the previous discrete circuit.
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 2-1176 has been designed so that selecting higher ratios also raises the threshold level.
The Technical Stuff __________________________________________________________ Output (Makeup Gain) Finally, output controls are employed to make up for the gain reduction applied by the gain reduction circuitry; on the 2-1176, this is the function of each channel’s Output knob.
The Technical Stuff _______________________________________________________________________ 1. While in Link mode, send stereo signal to the 2-1176 but monitor the left channel only. 2. In the left channel of the 2-1176 only, set the Ratio switch as desired and adjust the Input and Output knobs until the desired amount of compression or limiting is heard. 3. Duplicate those same settings in the right channel of the 2-1176 and then begin monitoring both channels, in stereo. 4.
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 2-1176 to the insert point on your mixer.
The Technical Stuff __________________________________________________________ Maintenance Information Meter Calibration The 2-1176 meters may occasionally need to be calibrated. This is accomplished by adjusting the Zero Set potentiometer, located through a small hole on the front panel between each channel’s Input and Output knobs. The procedure for adjusting the meter is as follows: 1. Power on the 2-1176. 2. Set the Meter switch for the channel being calibrated to its +4 position. 3.
The Technical Stuff __________________________________________________________ Changing Fuses The AC power fuse is located on the power supply circuit board inside the 2-1176, directly behind the AC power connector, accessed by removing the top panel of the 2-1176. Always remove the power cord before checking or changing the fuse! The required fuse is a T2A 250V, 5mm x 20mm.
The Technical Stuff __________________________________________________________ 2-1176 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 1176 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 1176, 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 1176 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 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 _______________________________________________________________________ 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 2-1176 gain reduction is program dependent. Ratio - see “Compression Ratio” Release time - The time it takes for a signal to return to its initial (pre-compressed) level.
Recall Sheet __________________________________________________________ - 33 -
Specifications _______________________________________________________________________ Input Impedance 15 kΩ, 600 Ω selectable Output Load Impedance 600 Ω (floating) Frequency Response 20 Hz to 20 kHz ± 1 dB Gain 40 dB, ± 1 dB Distortion > 0.5% T.H.D. from 50 Hz – 15 kHz with limiting, at 1.1 seconds release setting. Output of +20 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.com.
