Model LA-610 Channel Strip Universal Audio Manual Number 65-0901 Revision 1.00 Universal Audio, Inc. www.uaudio.com 330 Encinal St. Santa Cruz, CA 95060 (831) 466-3737 voice (831) 466-3775 fax www.uaudio.com The LA-610 Channel Strip Thank you for purchasing the LA-610 Channel Strip. This unit combines a modified channel of our 2-610 Mic Pre with an LA2A style T4 Optical Compressor. Our 610 was inspired by the microphone preamp section of the 610 tube console designed by my father, M.T. "Bill" Putnam, in the 1950s. The 610 was a rotary-control console and was the first console of the modular design. Although technologically simple compared to modern consoles, the 610 possessed a warmth and character that kept it in demand for decades. As a prominent part of my father's United/Western studios, the 610 was used on many classic recordings by Frank Sinatra and Sarah Vaughan. The Beach Boys Pet Sounds, the Doors LA Woman, and Van Halen's debut album were all recorded on the 610. The legendary Wally Heider used the 610 in his remote truck for many of his best-known live recordings. At Ocean Way Studios (formerly United), the 610 is lovingly preserved and still used in Studio B. The T4 Compressor element in the LA-610 is identical to the circuit components housed inside the T4 optical cell used on the legendary LA2A compressor. The heart and soul of the LA-2A is mostly a result of this special optical gain control element. The unique and musical behavior of the LA-2A is present in the LA-610 as well, the main difference being a more colored sonic signature with the LA-610. Unlike the LA-2A, the LA-610 offers a wide variety of tone and character by virtue of the dual stage level controls and EQ section. The incredible price/value of the LA-610 is the result of using the existing 610 tube amplifier and simply adding the T4 optical element creating a mono channel strip that can serve as a mic or Instrument preamp with or without EQ and compression. In addition, the LA-610 has a line level input for use as a dedicate compressor with or without EQ and tube saturation. In addition to the LA-610, Universal Audio has released reproductions of the classic Teletronix LA-2A Leveling Amplifier and 1176LN Limiter as well as the 610 tube preamp and 2108 microphone preamplifier, which is based on the 1108 line amps that were used in my father's studios. Universal Audio also creates software emulation's of our vintage hardware that run on our UAD-1 DSP card as well as Digidesign's Pro Tools platform. All of these products are designed to meet the demands of the modern recording studio, yet retain the character of vintage equipment. Please visit www.uaudio.com to see and read about other great recording tools from Universal Audio. ii These products have been quite an enjoyable adventure to develop and we're sure the next phase will be even more fun! We thank you for your support and we thank my father, Bill Putnam. Thank you, Bill Putnam iii 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. 2. 3. Water and Moisture ­ Do not use the unit near any source of water or in excessively moist environments. Object and Liquid Entry ­ Care should be 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 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 heat sources, or other equipment that produce heat. Power Sources ­ The unit should be connected 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 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 cords 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 equipped with a 3-wire grounding type plug, a plug having a third (grounding) 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. 8. 4. 5. 6. 7. Carts and Stands ­ The unit should be used 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 a qualified service personnel when: a) The AC power supply cord or the plug has been damaged: or b) Objects have fallen or liquid has been spilled into the unit; or c) The unit has been exposed to rain; or d) The unit does not operate normally or exhibits a marked change in performance; or e) The unit has been dropped, or the enclosure damaged. 13. Servicing ­ The user should not attempt to service the unit beyond that described in the operating instructions. All other servicing should be referred to qualified service personnel. iv Notice This manual provides general information, preparation for use, installation and operating instructions for the Universal Audio LA-610 Channel Strip. 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. 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 © 2004 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, 1176LN, 2-610, 2108, 6176, 2-1176, LA-610 and the Universal Audio, Inc. logo are trademarks of Universal Audio, Inc. Other company and product names mentioned herein are trademarks of their respective companies. v Table Of Contents LA-610 Specifications .............................................................................. 1 LA-610 Operating Instructions ............................................................... 2 610 Front Panel .......................................................................... 2 Input Select ........................................................................ 2 Gain ..................................................................................... 3 Level..................................................................................... 3 Pad....................................................................................... 4 Polarity................................................................................. 4 +48 V (Phantom Power) .................................................. 4 EQ Controls......................................................................... 4 T4 Optical Compressor Front Panel ......................................... 5 Peak Reduction ................................................................. 5 Gain ...................................................................................... 5 Limit/Compress................................................................... 5 Meter Function ................................................................... 6 Meter Calibration .............................................................. 6 Meter Function ................................................................... 6 Meter Calibration .............................................................. 6 LA-610 Rear Chassis ................................................................................. 6 Input/Output ................................................................................. 6 AC Power ...................................................................................... 7 Fuse/Mains ..................................................................................... 7 Voltage Select .............................................................................. 7 Compressor Theory of Operation ..........................................................8 Compressor Basics ....................................................................... 8 Gain Reduction Circuits.............................................................. 8 Historical Notes ........................................................................................13 The 610 Preamp .......................................................................... 13 The 1176 and LA-2A Compressors .......................................... 15 The LA-2A ..................................................................................... 16 vi LA-610 Specifications Microphone Input Impedance Balanced Line Input Impedance Hi-Z Input Impedance Maximum Microphone Input Level Maximum Output Level Internal Output Impedance Recommended Minimum Load Frequency Response Maximum Gain Noise Floor Tube Complement Selectable, 500 or 2k 20k Selectable, 2.2M or 47k -8 dBu (2K input Imp. & 15 dB Pad in) +20 dBu (120Vac line) 80 600 20 Hz to 20 kHz +/- 0.5dB 40 dB (Line), +77dB (Mic) -72 dBu 20 ­ 20kHz (Line In, Unity Gain) (3)12AX7, (1)6072, (1)6AQ5 General: Power Requirements: Dimensions: Weight: 115V / 230V operation 3.5" vertical, 19" rack (2RU). 12 lbs. (Boxed,14.5 lbs.) 1 LA-610 Operating Instructions The LA-610 is a vacuum-tube microphone/instrument/line preamplifier with basic EQ and an optical program dependent compressor. The main preamp circuit has two gain stages that utilize a dual-triode tube operating in a class A single-ended configuration. Variable negative feedback is applied to both of these stages to control gain, distortion, and frequency response. Balanced inputs and outputs are transformer coupled. 610 Front Panel (left side) This panel has the Input Select, Gain, Level, EQ, Pad, Polarity and +48 volt Phantom controls as well as a Hi-Z Input. Each control is discussed in the following sections. -15 dB GAIN -5 0 +5 -10 +10 LEVEL 4 3 5 7K 6 7 8 1 9 0 10 Tube Mic Pre 200 70 100 10K 4.5K HIGH -3 -4.5 -6 -1.5 0 +1.5 +3 +4.5 +6 -9 +9 OUTø PAD Mic 500 Line Hi-Z 47K 2.2M IN ø 2.0K +48V 2 LOW -3 -4.5 -6 -1.5 0 +1.5 +3 +4.5 +6 -9 +9 OFF Hi-Z Figure 1: 610 Front Panel Input Select The Input Select switch determines which input is active: Mic, Line, or Hi-Z. Within both the Mic and Hi-Z areas, the switch includes two settings to select different input impedances. · Mic: Selects the signal from the rear-panel, balanced, MIC INPUT XLR connector. The impedance for the MIC INPUT can be set to 500 or 2K . Switching between these two positions while listening to a connected microphone may reveal a different tonal quality and / or gain. A typical mic preamplifier should have an input impedance 2 equal to about 10 times the mic output impedance. For example, if your mic has an output impedance between 150 and 200 , set the switch to the 2K position. However, since making music is not necessarily about adhering to technical specifications, feel free to experiment with the settings to attain the desired sound. You will not harm your microphone or the LA-610. · Line: Selects the signal from the rear-panel, balanced, LINE INPUT XLR connector. LINE INPUT has an input impedance of approximately 13 k ohms and is intended to accommodate mixers, tape machines, other mic preamps or any device with a line level output, such as keyboards, sound modules and drum machines. The LA-610 may be used as a "tone box" in this configuration, offering a variety of sonic colors based on the front panel control settings. Hi-Z: Selects the signal from the front panel, unbalanced Hi-Z 1/4"connector. This input can have an input impedance of 47K or 2.2M and is intended for bass, ...