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Symetrix 425 Owner's Manual

Dual compressor / limiter
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Signal Processing at it's Best!
Revision 2.0, 10/29/93
Part number: 530201
Subject to change at our whim, and without notice.
Copyright 1992–1993 by Symetrix Inc. All rights Reserved.
Batteries not included. Void where taxed or prohibited. Ground ain't ground!
Symetrix
Symetrix
" #
Dual Compressor / Limiter
Owner's Manual

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  • Page 1 Owner’s Manual Signal Processing at it’s Best! Revision 2.0, 10/29/93 Part number: 530201 Subject to change at our whim, and without notice. Copyright 1992–1993 by Symetrix Inc. All rights Reserved. Batteries not included. Void where taxed or prohibited. Ground ain’t ground!

  • Page 2: Table Of Contents

    6.5 Stereo Coupling....................6-2 7. Using the 425..................7-1 7.1 Block Diagram ....................7-1 7.2 Installation ......................7-1 7.3 The 425 as a Compressor ................7-1 7.4 The 425 as a Ducker ..................7-2 7.5 The 425 as a Limiter..................7-2 7.6 The 425 as an Expander ................7-3...
  • Page 3 8.4 Paging with Ducking ..................8-2 8.5 Stage Monitors ....................8-2 8.6 Keyed Bass ....................8-3 8.7 Sibilance Control ....................8-3 9. Troubleshooting Chart................ 9-1 10. 425 Dual Compressor Limiter Limited Warranty ......10-1 11. Repair Information................11-1 11.1. Return Authorization..................11-1 11.2. In-Warranty Repairs..................11-1 11.3. Out-of-Warranty Repairs................11-1 12.

  • Page 4: Introduction

    At Symetrix, we feel that the 425 represents the distillation of our 15 years of signal processing experience into a product that is at once versatile and easy to use without having important controls removed in the interest of simplicity.

  • Page 5: Operator Safety Summary

    Chapter 7. Using the 425: describes the use of the 425 in detail. Chapter 8. Applications: gives some hints for using the 425 in a variety of situations and provides a short introduction to dynamics processing.. Chapter 9. Troubleshooting: tells what to do when the 425 doesn't work.

  • Page 6: Terms

    Convention Description Identifies information that, if not heeded, may cause Caution damage to the 425 or other equipment in your system. Identifies information that needs extra emphasis. A NOTE Note generally supplies extra information to help you use the 425 better.
  • Page 7 Do not operate the product without the covers and panels properly installed. User-serviceable parts There are no user serviceable parts inside the 425. In case of failure, refer all servicing to the factory. Rev 2.0, 10/29/93...

  • Page 8: Dynamics Processing Tutorial And Functional Basics

    VCAs. This part of the 425 tells how to use your 425. If you are new to signal processors, read on; the remainder of this section is a primer on the three basic parts of the 425.

  • Page 9: Expanders And Gates

    2.1.3 Ratio The compression ratio of the 425 tells how much the output changes for a change in the input. A linear amplifier (like a simple preamp) has a ratio of 1:1 because a change of 1 dB at its input results in a 1 dB change at its output.

  • Page 10: Release Time

    The sidechain is a patch point in the control circuit of a dynamic range processor, which provides access to the part of the circuitry that tells the VCA what to do. The 425's sidechain is routed through a TRS jack located on the rear panel that provides both a send and return via the same jack.
  • Page 11 The best use of the sidechain is to make the action of the 425's compressor/limiter/expander frequency dependent, that is, to make it respond more (or less) to certain frequencies. Because...
  • Page 12 (instead of the 425's output) that you're using in the sidechain. Doing this allows you to hear the signal that will control the 425, and perhaps to find the range that you wish to emphasize or de-emphasize more easily.
  • Page 13 Notes Rev 2.0, 10/29/93...

  • Page 14: Technical Tutorial

    Technical Tutorial This section discusses a multitude of things, all related to getting signals in and out of the 425. 3.1. Matching Levels vs Matching Impedances In any audio equipment application, the question of "matching" inevitably comes up. Without digging a hole any deeper than absolutely necessary, we offer the following discussion to (hopefully) clarify your understanding of the subject.

  • Page 15: Signal Levels

    2 to 200 times the output source impedance) your outputs. 3.2. Signal Levels The 425 is designed around studio/professional line levels: +4 dBu or 1.23 volts RMS. The unit is quiet enough to operate at lower signal levels such as those found in semi-pro or musical-instrument (MI) equipment (-10 dBu or 300 millivolts).

  • Page 16: Input And Output Connections

    In an emergency (the show must go on), you can ground pin 3, but if you have the choice...leave it open. If you must ground pin 3, it is must be grounded at the 425, rather than at the other end of the cable. The price, regardless of whether or not pin 3 is grounded is 6 dB less output level.
  • Page 17 TERMINAL STRIP (+) = HIGH (-) = NOT USED = GROUND FROM NON-TRANSFORMER (ELECTRONIC) BALANCED OUTPUT (TYPICAL OF SYMETRIX PRODUCTS) TO UNBALANCED IN MALE TS PLUG FEMALE XLR TIP = HIGH PIN 1 = GROUND + LOW SLEEVE = GROUND +...

  • Page 18: Front Panel Overview

    SLOW BYPASS FAST SLOW BYPASS The 425 has the following controls, switches, and indicators on its front panel: Expander Sets the signal level below which the expander begins to HRESHOLD operate. When the input signal falls below the level indicated on the knob, the expander begins reducing the gain.
  • Page 19 Indicates the output level of the 425. This switch bypasses the 425. This is NOT a hard-wire bypass; IN/BYPASS the 425 will not pass signal unless the unit is powered and turned on. This switch selects dual-mono or stereo-coupled mode. In...

  • Page 20: Rear Panel Overview

    SEATTLE WASHINGTON, IN/OUT UNITED STATES OF AMERICA The following connectors and features are found on the rear panel of the 425. Serial Number Do yourself a favor and write this number down somewhere safe, and while you're at it, please send us the completed...
  • Page 21 Notes Rev 2.0, 10/29/93...

  • Page 22: Fast First Time Setup

    6. Fast First Time Setup Follow these instructions to get your 425 up-and-running as quickly as possible. The intent of this section is fast setup. If you need something clarified, then you'll find the answer elsewhere in this manual. 6.1 Connections Connect the line-level signal source to either the female XLR connector or the 1/4 inch TRS (tip-ring-sleeve, stereo, 3 conductor) input jack.

  • Page 23: Settings

    6.3 Initial Setup The 425's controls and switches are now set according to the preceding section. All connections listed in Section 6.1 are now made. The 425 should now pass signal. The LED display should be illuminated. Set the input level by increasing the setting of the input level control until the amber LEDs in display illuminate.

  • Page 24: Stereo Coupling

    May we suggest using the compressor with the ratio control set at maximum. Stereo Coupling If you are using the 425 for a stereo signal, say for a stereo mixdown, depress the switch so that the LED is lit.
  • Page 25 Notes Rev 2.0, 10/29/93...

  • Page 26: Using The 425

    7. Using the 425 The 425's design emphasizes ease-of-use. This doesn't mean that we made it easy to use by removing everything except the power switch; instead we concentrated on keeping the controls that really make a particular feature work well and eliminating those that didn't. This section contains installation information and descriptions of each of the front and rear panel controls, switches, and connectors.

  • Page 27: The 425 As A Compressor

    Now for some people, a "true" ducker must reduce the level of the duckee to some preset level whenever the ducker signal is present. The 425 will not do this. It will,however, reduce the level of the duckee whenever the ducker is present, but the amount of gain reduction follows the envelope of the ducker signal.

  • Page 28: The 425 As A Limiter

    20+ dB of gain reduction to be effective. 7.5 The 425 as a Limiter The peak limiter section of the 425 is a fast-acting (200µS), steep slope (20:1) limiter. Peak limiters are generally used to stop signal peaks dead in their tracks. The peak limiter in the 425 has only one control: threshold.
  • Page 29 Another application for simultaneous expanding and compressing is voice processing. Close mic'ed voices tend to be a little un-natural. Things that we don't hear at conversational distance are heard quite well by the announce microphone. A bit of expansion will help to reduce lip-smacking noises and some compression will help even levels out and generally tighten up the sound.

  • Page 30: Applications

    8. Applications Here are a few applications that the 425 lends itself to. The following applications make one assumption: settings for the threshold control(s) are a function of each individual system's actual operating level. Wherever specific threshold settings are mentioned, they are referenced to either a particular gain reduction level as indicated by the meter, or to a O dBu input level.

  • Page 31: Paging With Ducking

    By splitting the host signal, part of it can be used to tell the 425 when to take action and lower the background source by an amount determined by the threshold control.

  • Page 32: Keyed Bass

    Use the release control to make the expander follow the music. 8.7 Sibilance Control Patching an equalizer into the sidechain can cause the 425 to respond more or less to selected frequencies, giving it the ability to make sibilance problems less apparent. Fine tuning between the compressor threshold, ratio, and the EQ boost applied in the sidechain will have to be made to arrive at premimum results.
  • Page 33 Notes Rev 2.0, 10/29/93...

  • Page 34: Troubleshooting Chart

    Are the power amplifier(s) clipping? Is something else clipping? Noise (hiss) Check input signal levels. The 425 is intended to operate at or near "line" level (-10 dBu or greater). Check gain settings on downstream equipment. The system gain structure should be such that the 601 operates at or near unity gain.
  • Page 35 Notes...

  • Page 36: Dual Compressor Limiter Limited Warranty

    In no event will Symetrix be liable for any incidental or consequential damages including but not limited to damage for loss of...
  • Page 37 Notes 10-2...

  • Page 38: Repair Information

    11.1 Return Authorization Symetrix will service any of its products for a period of five years from the date of manufacture. However, no goods will be accepted without a Return Authorization number. BEFORE SENDING ANYTHING TO SYMETRIX, CALL US FOR AN RA NUMBER. JUST ASK, WE'LL GLADLY GIVE YOU ONE! CALL (206) 282-2555 WEEKDAYS, 8AM TO 4:30 PM PACIFIC TIME.
  • Page 39 Notes Rev 2.0, 10/29/93 11-2...

  • Page 40: Specifications

    12. Specifications Input/Output Inputs XLR-female, >30-kilohms line-level balanced bridging, >30-kilohms unbalanced bridging. TRS-female paralleled with XLR connector. Outputs 300-ohm source impedance, balanced. XLR-male TRS-female wired tip hot, ring & sleeve grounded (unbalanced), 150- ohm source impedance. Maximum input level +20 dBu, balanced Maximum output level (onset +25 dBu balanced of clipping/1% THD)
  • Page 41 117V AC nominal, 105-125VAC 50-60 Hz, 12.5 Watts maximum 230V AC nominal, 205-253V AC 50 Hz, 12.5 Watts maximum In the interest of continuous product improvement, Symetrix Inc. reserves the right to alter, change, or modify these specifications without prior notice. Rev 2.0, 10/29/93...

  • Page 42: Pcb Layouts And Schematics

    Symetrix Service Department at the address listed in Section 11 of this manual. 13.1 Troubleshooting Hints If you are attempting repair of your 425, the following tips and hints may be useful, especially if you are not familiar with operational amplifiers.
  • Page 43 UNBALANCED SWITCH INPUT INPUT IN/OUT OUTPUT OUTPUT INPUT INPUT IN/OUT OUTPUT OUTPUT P/N 022001 REV ’E’ COPYRIGHT 1991 SYMETRIX, INC. OPTIONAL 022001 REV E A.C. SWITCH CAUTION HAZARDOUS VOLTAGE COMPONENT SIDE SIDECHAIN INPUT OUTPUT SIDECHAIN INPUT OUTPUT OUTPUT OUTPUT INPUT...
  • Page 44 ADDED C4 & C5 IN TOUCH-UP (ECO #169) 2/13/92 NYLON STANDOFFS NOW METAL 7/6/93 BOARD REV’D TO REV ‘C’ (ECO #170) 3/10/92 COPYRIGHT 1991 P/N 022002 REV ’D’ 022002 REV ’D’ SYMETRIX, INC. MOTHERBOARD MOTHERBOARD COMPONENT SIDE SCREW ACCESS SCREW ACCESS MOTHERBOARD SCREW ACCESS R162...
  • Page 45 2 / 1 3 / 9 2 100pF XLR-FEMALE RESISTORS AND CAPS AS PER ECO 170 3 / 9 / 9 2 BALANCED 2150A RESISTORS AND CAPS AS PER ECO 425-002 7 / 2 1 / 9 2 13K0 15K0 OUTPUT 2K00 13K0...
  • Page 46 SYMETRIX INC. 6K98 (BYPASS) 10K0 1N4148 4 K 7 4211 24th Ave W SEATTLE, WA 98199 +15VA 7 5 K REV: T I T L E : -15VA DRAWN: 425 DUAL COMP/LIMITER/EXPANDER DATED: DRAWING NO: 022001-SCH RELEASED: DATED: SHEET: -15VA...
  • Page 47 BP18 .1uF .1uF .1uF .1uF .1uF .1uF .1uF .1uF .1uF .1uF -15VA COMPANY: SYMETRIX INC. 4211 24th Ave W SEATTLE, WA 98199 REV: T I T L E : DRAWN: DATED: 425 DUAL COMP/LIMITER/EXPANDER DRAWING NO: RELEASED: DATED: 022001-SCH SHEET:...
  • Page 48 THRESHOLD TRIM -15VA 1N4148 R158 1N4148 100K 1K00 10K0 R164 220K +15VA COMPANY: SYMETRIX INC. 4211 24th Ave W SEATTLE, WA 98199 REV: T I T L E : DRAWN: 425 DUAL COMP/LIMITER/EXPANDER DATED: DRAWING NO: 022001-SCH SHEET: RELEASED: DATED:...
  • Page 49 50KB 300K OUTPUT LEVEL 6K98 4.7NP (FRONT PANEL) S/C_JACK_CH2 -15VA R103 100K COMPANY: SYMETRIX INC. 4211 24th Ave W SEATTLE, WA 98199 T I T L E : REV: DRAWN: 425 DUAL COMP/LIMITER/EXPANDER DATED: DRAWING NO: RELEASED: DATED: SHEET: 022001-SCH...
  • Page 50 249K0 (FRONT PANEL) R151 24K3 R147 10K0 -15VA 1N4148 1N4148 R152 1K00 COMPANY: SYMETRIX INC. 4211 24th Ave W SEATTLE, WA 98199 REV: T I T L E : DRAWN: DATED: 425 DUAL COMP/LIMITER/EXPANDER DRAWING NO: 022001-SCH RELEASED: DATED: SHEET:...
  • Page 51 CH2 EXPANDER SIDE CHAIN 1N4148 4 K 7 RC4560 4211 24th Ave W +15VA R205 SEATTLE, WA 98199 R203 REV: 7 5 K T I T L E : -15VA R206 425 DUAL COMP/LIMITER/EXPANDER DRAWN: DATED: DRAWING NO: RELEASED: DATED: SHEET: 022001-SCH -15VA...
  • Page 52 7 / 9 / 9 2 120 OHM 120 OHM 120 OHM ECO 425-8 SWAPPING LED REF DES. 8 / 2 4 / 9 3 D 4 0 - D 4 3 & D 6 0 - D 6 3 B.G.
  • Page 53 (RED) 4211 24th Ave W - 2 5 d B LM339 +15VA SEATTLE, WA 98199 REV: T I T L E : R 5 4 124K 425 LED DAUGHTERBOARD DRAWN: DATED: (RED) DRAWING NO: SHEET: -15VA RELEASED: DATED: 022002-SCH CH2 COMPRESSOR LEDS...
  • Page 54 LM339 LM339 LM339 U12B AGND RC4560 AGND AGND .1uF .1uF COMPANY: SYMETRIX INC. -15VA 4211 24th Ave W SEATTLE, WA 98199 REV: T I T L E : 425 LED DAUGHTERBOARD DRAWN: DATED: DRAWING NO: AGND 022002-SCH SHEET: RELEASED: DATED:...
  • Page 55 13-4...

  • Page 56: Appendix A. Architects And Engineers Specification

    The unit shall be capable of operating by means of its own built-in power supply connected to 117V nominal AC (105-130V) 50/60 Hz (230V nominal, 207-253V AC, 50 Hz where applicable). The unit shall be a Symetrix Incorporated model 425 Dual Compressor/Limiter/Expander. Rev 2.0, 10/29/93...
  • Page 57 Notes Rev 2.0, 10/29/93...

  • Page 58: Appendix B. Disassembly Instructions

    5/64" allen wrench. Top Cover Removal Ensure that the 425 is disconnected from the AC power source. Remove four 6-32 x 1/2 inch screws from the rear-panel. Remove two 6-32 x 1/2 inch screws from each side of the chassis.
  • Page 59 Notes Rev 2.0, 10/29/93...

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