THE STC-8 DISCRETE CLASS A STEREO COMPRESSOR-PEAK LIMITER OPERATOR'S MANUAL Version 1.2 CRANE SONG LTD. 2117 East 5th Street Superior, WI 54880 USA tel: 715-398-3627 fax: 715-398-3279 www.cranesong.com ©1996, 2009 Crane Song,LTD. Subject to change without notice. Printed in the U.S.A.
IMPORTANT SAFETY INSTRUCTIONS 1. Read these instructions 2. Keep these instructions 3. Heed all warnings 4. Follow all instructions 5. Do not use this apparatus near water 6. Clean only with dry cloth 7. Install in accordance with the manufacturer's instructions 8. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat 9.
TABLE OF CONTENTS ...........................................PAGE 2 Class A ................................................ Heating and Warm-up ........................... 2 2 PANEL REFERENCE ..................................... 3 CONTROL DESCRIPTION .............................. Preset Switch Layout ............................. 4 Input/Output GR Graphs ........................ 5 7 DISTORTION AND COMPRESSORS ............... 8 COMPRESSOR QUICK GUIDE ....................... The "V" Setting ...............
PAGE 2 INTRODUCTION The STC-8 is a high quality compressor combined with a remarkably dependable peak limiter, that provides overload protection critical to digital recording and broadcast transmitters. The STC-8’s compressor is engineered to provide musically transparent gain control, but is also capable of emulating vintage equipment and creating distinctive new sounds. In addition, a switchable enhancement circuit creates “analog” and “tube-like” warmth to enrich lifeless audio and digital recordings.
Slow (Variable Mode only) Both Channels COLOR BYPASS Compressor Make Up Gain ACTIVE IN V Fast Slow LEFT CHANNEL Amount of Gain Reduction Fast Referenced to output (Post Gain Control) LIMITER ONLY Slow or Aggresive Gain Reduction Curve Shape of Knee Gentle Slow RIGHT CHANNEL Fast Fast PANEL REFERENCE PAGE 3
PAGE 4 CONTROL DESCRIPTION THRESHOLD The threshold control governs the amount of gain reduction. The compressor initially has a “softknee” compression curve but is increased by the shape control. PK THRESHOLD The peak threshold control sets the level at which the peak limiting takes place. The slope is greater than 10:1 and is fast enough to prevent overload of a transmitter or digital recorder.
CONTROL DESCRIPTION (Cont.) PAGE 5 The Dynamic Attack Modification groups are located at the upper right and lower left sections of the preset matrix. With either A-MOD group enabled, the peak limiter will dynamically modify the attack time of the compressor function. When a slower attack time (3 or higher) is selected on the compressor, any signal triggering the peak limiter automatically shortens the attack time of the compressor.
CONTROL DESCRIPTION (Cont.) PAGE 6 STEREO LINK SWITCH When in the link mode the gain control, bypass switches, and meter switches still operate independently. All other functions are operated by the Channel 1 controls. BYPASS SWITCH The bypass switch selects the output signal source. When the unit is bypassed all of the compressor circuitry is removed from the audio path. However, the compressor-limiter continues to operate in a monitoring mode.
CONTROL DESCRIPTION (Cont.) PAGE 7 SHAPE CONTROL The shape control changes the gain curve, the relationship between amount of gain reduction taking place and the signal level. The input to output ratio changes as a result of this. With the control set to 0 the curve and slope are gentle. With the control set to 10 the curve is more aggressive and the slope is higher. INPUT/OUTPUT GAIN RELATIONSHIP GRAPH (Graph 1) In the graph at left, two groups of curves show gain reduction, groups A and B.
CONTROL DESCRIPTION (Cont.) PAGE 8 METER The meter has three modes of operation. In the output mode the meter appears as a bar graph. 0 VU is referenced to +4dBm. In the PK mode the meter appears as a dot and shows the amount of head room by showing peak level below clipping. The third mode shows gain reduction. This also appears as a dot type display. The red OL LED lights with clipping in the output stage and the green PK LED lights when the PK side chain takes control from the average side chain.
PAGE 9 THE COMPRESSOR "QUICK GUIDE" To set up the Compressor quickly use the Presets A, B, or C. In these modes the Attack, Release, and Shape controls are not operational. Leave the Pk Threshold in the off position. With Pk Threshold left in off position, the only decision regarding the Preset Switch is whether or not to use Program Dependent Release (PDR). PDR is the left half of the Preset Switch, non-PDR is the right half. (See Preset Switch layout, page 5) PDR can be thought of as Auto Release.
PAGE 10 Table A below shows the relationship between the A, B, and C Presets and the Variable settings. This is useful information when starting with a preset and then wanting to fine tune for a particular sound. APPROXIMATE PRESET SETTINGS AND THEIR RELATIONSHIP TO THE VARIABLE MODE Preset Attack Release Shape A 2 5.5 3.5 B 6.5 6 1 C 6.25 7 5 Table A *NOTE It is important to note that the Gain Reduction curve , as determined by the shape control, modifies the attack and release times.
PAGE 11 COMBINED COMPRESSOR-LIMITER When the limiter is set to operate with the compressor, the green peak LED will light when the limiter takes control. It is recommended that the limiter be used in conjuction with the compressor. THE ATTACK MODULATION DECISION Attack modulation (A-Mod) is in the upper right corner and lower left corner on the preset switch (see Preset Switch layout, page 5). Using A-Mod will help prevent the chopped off limited type of sound that occurs when a source is peak limited.
PAGE 12 The following chart is an attempt to show what happens with the A, B, and C Presets. For the purpose of the measurements in the chart, the compression range is from no gain reduction to 12 dB of gain reduction. Numbers in the chart are approximate. Ratio conditions are as indicated. *Ratio conditions relate to the entire specific preset section, not to Release Time and Conditons columns in the chart. i.e. Starting GR and Ratios in the A Preset section relate to the whole section.
PAGE 13 SIGNAL FLOW BLOCK DIAGRAM Input Amplifier INPUT Post Amplifier (SINGLE CHANNEL) Gain Amplifier Gain Control OUTPUT Side Chain Interface PWM and Control Signal Combiner Output Amplifier Compressor Side Chain Limiter Side Chain Meter Gain Control Bypass Relay
PAGE 14 INTERFACING Input: Floating, balanced. Maximum input is +25 dBm. The connectors are XLR. Output: Floating, balanced. Maximum output is +25 dBm. The connectors are XLR. For Input and Output : Pin 2 is Sig + , Pin 3 is Sig- , Pin 1 is GND Side Chain Connections: Floating, balanced. Connections are made by using a DB-15 Male Connector. This is a loop insert and must be normaled back to the STC-8.
PAGE 15 SPECIFICATIONS Compressor Attack Time: FAST; measured by doing 18 dB of Gain Reduction. The time to 18 dB of Gain Reduction is less than 1mS. 12 dB of the 18 are reached in .4mS. SLOW; for 6 dB of GainReduction, 100mS Compressor Release Time: FAST; From 12 dB of Gain Reduction to No Gain Reduction. 11 of 12 dB are reached in 50mS (Non Program Dependant Release) SLOW; 20 sec for a full 12 dB release with PDR enabled. Limiter Attack Time: less than 1uS.
PAGE 16 MODE SWITCH - KI SOUND AND OPTIONS A number of vintage compressors have a frequency response that changes with gain change. This is a result of changing circuit impedance and is typical of optical based compressors such as the LA-2A and similar devices. These devices will be flat with no gain reduction and become bright with gain reduction, or will loose hi end with no gain reduction and become flat with 6 to 12 db of gain reduction. It’s part of their sound and is highly prized by many people.
CRANE SONG LTD. 2117 E. 5th Street Superior, WI 54880 USA tel. 715-398-3627 fax. 715-398-3279 STC-8 DISCRETE CLASS A COMPRESSOR-LIMITER REGISTRATION FORM Please fill out this form and return it so we can send you updates and pertinent information as it becomes available. Thank you.
