User manual UNIVERSAL AUDIO LA-610

[. . . ] Model LA-610 Channel Strip Universal Audio Manual Number 65-0901 Revision 1. 00 Universal Audio, Inc. 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. [. . . ] On the right, the LA-610 MIC INPUT, LINE INPUT, and LINE OUTPUT XLR connectors. These connectors are discussed in the following sections. POWER IN: 115V ~ 50/60Hz 400ma 230V ~ 50/60Hz 200ma FUSE RATING: T 400ma L 115V~ T 200ma L 230V~ ! CAUTION / AVIS REPLACE FUSE WITH SAME RATING AND TYPE ONLY! RISK OF ELECTRIC SHOCK DO NOT OPEN RISQUE DE CHOC ELECTRIQUE NE PAS OUVRIR CE LINE OUTPUT LINE INPUT MIC INPUT CAUTION: TO REDUCE THE RISK OF FIRE OR ELECTRICAL SHOCK DO NOT EXPOSE THIS PRODUCT TO RAIN OR MOISTURE ATTENTION: POUR REDUIRE LE RISQUE DU FEU OU DE CHOC ELECTRIQUE N'EXPOSEZ PAS CE PRODUIT A LA PLUIE OU A L'CHUMIDITE' UNIVERSAL AUDIO, ·SANTA CRUZ, CALIF. USA INC Figure 3: LA-610 Rear Chassis Input/Output Standard XLR input and output connectors are provided on the rear panel. Pin 2 is wired positive (hot) on the LINE and MIC INPUTS. Pin 2 is positive on the LINE OUTPUT when the front panel Polarity toggle switch is down (IN ). Pin 3 is positive on the LINE OUTPUT when the front panel Polarity switch is up (OUT ). 6 AC Power The LA-610 uses a standard, detachable IEC power cable. Fuse/Mains The AC power fuse is located in the AC power connector block. Remove the power cord before checking or changing the fuse. A 400 mA time delay (slow blow) fuse is required for operation at 115 V. A 200 mA time delay (slow blow) fuse is required for operation at 230 V. Voltage Select The LA-610 can operate at 115 V or 230 V. To change the mode, wait 5 minutes after power down, unplug the AC power cord from the rear chassis. As shown below, the Voltage Select Cable can be plugged into one location for 115V operation or moved to the 230V Connector for 230V operation. This figure shows the unit configured for 115V operation. The connector is part of the wiring that comes from the power transformer located at the rear of the LA-610 next to the main AC power inlet. When changing operating voltage, the fuse value must be changed as well. Make sure the LA-610 is properly set for the voltage in your area before applying AC power to unit! Figure 4: 115V / 230V Voltage Select Jumper 7 Compressor Theory of Operation Compressor Basics Before we dig in to a description of the compressor circuit, it is useful to examine the general characteristics of compressors and review some terminology. The chart below (Figure 4) depicts the input/output characteristics of a compressor, an expander and a perfect amplifier. When operated within its specified range, an amplifier provides a constant amount of gain regardless of the level of the input signal. In figure 4 below, the middle line depicts a perfect amplifier with a gain of 10 dB. To see this, notice that a signal with an input level of ­30 dB will result in an output level of ­20 dB, which is an increase of 10 dB. Similarly, an input level of 0 dB will result in an output level of 10 dB, hence the gain stays fixed at 10 dB regardless of the input level. Expansion Perfect amplifier +10 0 Compression Output Level (dB) -10 -20 -30 -30 -20 -10 0 +10 Input Level (dB) Figure 4- Input/output characteristics of a compressor, an expander and a perfect amplifier. [. . . ] The character of the mic-pre in particular made it favorite of engineers like Bruce Swedien, Bruce Botnick, Lee Hirschberg and Jack Joseph Puig; and artists including Sarah Vaughan, Frank Sinatra, Ray Charles, and The Beach Boys. Swedien describes the character of the preamp as "clear and open" and "very musical". Studios 2 and 3 at Western, which featured the 610 console, were the site of many classic recordings of the 60's, including the Mamas and the Papas (Bones Howe), Up, Up and Away by the Fifth Dimension, Herb Alpert, Sergio Mendes (Bruce Botnick), and of course Pet Sounds. Legendary engineer Wally Heider, manager of remote recording at United, used his 610 console to record many live recordings including Peter, Paul and Mary "In Concert" (1964), Wes Montgomery's "Full House" (1962), and all of the Smothers Brothers Live albums. [. . . ]