Crane Song STC-8 User Manual

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: [phone]

fax: [phone]

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. K eep 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. Protect the po w er cord from being w alked on or pinched particularly at plugs and the
point where they exit from the apparatus

10. Only use attachments/accessories specified by the manufacturer

11. Unplug this apparatus during lightning storms or when unused for long periods of
time

12. Refer all servicing to qualified service personnel. Servicing is required when the
apparatus has been damaged in any way, such as power-supply cord or plug is dam­aged, liquid has been spilled or objects have fallen into the apparatus, the apparatus
has been exposed to rain or moisture, does not operate normally, or has been dropped

13. CAUTION: To disconnect the unit completely from the MAINS , unplug the unit. Turn­ing the power switch off does not disconnect the unit completely from the MAINS.

TABLE OF CONTENTS

INTRODUCTION ...........................................

Class A ................................................

Heating and Warm-up ...........................

PANEL REFERENCE .....................................

CONTROL DESCRIPTION ..............................

Preset Switch Layout .............................

Input/Output GR Graphs ........................

DISTORTION AND COMPRESSORS ...............

COMPRESSOR QUICK GUIDE .......................

The "V" Setting ......................................

Preset Settings .....................................

FAST SET-UP OF THE PEAK LIMITER ............

COMBINED COMPRESSOR LIMITER ..............

The Attack Modulation Decision ............

"NUMBERS" .................................................

Presets ................................................

BLOCK DIAGRAM .......................................

INTERFACING .............................................

SPECIFICATIONS .........................................

MODE SWITCH - KI SOUND AND OPTIONS...... 16

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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. This vast flexibility is simplified by the inclusion of several
optimized presets, allowing fast, easy set-up on a wide variety of sounds. It can operate in true
stereo or discrete independent mono, accessible by a front panel switch.

The STC-8’s sophisticated side-chain allows both compression and peak limiting to take place
simultaneously, using the same proprietary gain control circuit. High signal quality is maintained
by utilizing a discrete class A audio path, and by eliminating any VCA or optical gain control
elements.

The STC-8 requires 2 rack spaces. All inputs and outputs are transformer-less and balanced.
The toroidal power transformer is UL approved and allows four line voltages for international use.
The STC-8 delivers consistent gain control without sacrificing musical definition or har­monic richness.

CLASS A DISCRETE TOPOLOGIES

The STC-8 has a Class A audio path which is significantly different than designs that use inte­grated circuits. Class A circuits sound better because their distortion components tend to be
Second Harmonic; musically pleasing. IC Op-Amps do not have class A output circuits and their
distortion components tend to be high order odd harmonics; not musical. The most important
thing to remember about Class A circuits is that they sound better.

This type of technology has 2 disadvantages when compaired to IC designs. 1) Due to the large
number of parts in discrete circuits; they are costly. 2) Class A circuits run warm.

HEATING AND WARM-UP

The STC-8 must have adequate ventilation. Make sure the vent holes are not blocked. Do
not set anything directly on top of the STC-8. When mounting the STC-8 in a rack, provide as
much air flow as possible. Leaving the back of the rack open is another option. If you provide
adequate ventilation, you will be rewarded with years of reliable operation.

All precision electronic equipment has an operating temperature that when reached will result
in best performance. The STC-8 should be allowed a 10 to 15 minute warm up period before
use.

PANEL REFERENCE PAGE 3

Aggresive

or

Curve

BYPASS

Gain

Make Up

Compressor

Slow

Fast

Fast Slow

Slow

Shape of Knee

Gentle

Gain Reduction

Both

COLOR

RIGHT CHANNEL

Channels

LIMITER ONLY

(Post Gain Control)

Referenced to output

Slow

Fast

Fast

ACTIVE IN V

(Variable Mode only)

Amount of

Gain Reduction

LEFT CHANNEL

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.
When a signal’s peak is greater than the average gain reduction, the peak circuit will take control
until the peak has passed, and then smoothly transfer regulation back to the compressor. The
green pk LED will light when the peak circuit is active.

When the Pk Threshold Control is set to +20 dBm, the limiter will prevent any increase in output
level above that setting. The output will remain constant even if the gain of the STC-8 is in­creased. The limiter circuit is post gain control. The dial callibration relates to the maximum
output level.

GAIN CONTROL

The gain control will adjust the compressor gain from 0 to 14 dB of gain. When in stereo link
mode the gain controls operate independently to allow balancing of the stereo program source.

SIDE CHAIN

The side chain consists of two control circuits, one for peak control and one for compression
control. The side chain insert only affects the average or compressor circuits. Due to the design
of the stereo link, separate equalizers (with identical settings) must be used for both channels to
achieve channel matched operation. This scheme allows reliable signal averaging regardless of
the phase relationship between the audio channels. In a conventional stereo link circuit (one EQ
for both channels) out of phase material is ignored by the compressor. This is also beneficial for
stereo FM broadcast where phase relationships can affect the stereo generator.

PRESET SWITCH

The preset rotary switch allows fast and predictable set-up of the STC-8. At first glance this knob
may look a bit forbidding, but in operation, this switch is the key to the flexibility and foolproof
operation of the compressor-limiter.

The STC-8 features two advanced functions: 1)Program Dependent Release (PDR) and 2) Dy­namic Attack Modification (A-MOD). The four groups of presets simply give every combination of
these settings. Further, each group has three presets with predetermined, optimized attack,
release and shape settings and one variable setting (which activates the front panel controls).

In the left half of the settings the Program Dependent Release is enabled. This function is espe­cially well suited for leveling the volume of the audio without bringing up background noise. It is
especially helpful controlling voice over, lead vocal and any other complex program material
where short release times tend to bring out room noise and headphone leakage. The right half of
the switch has constant release times, useful for enhancing the sustain of guitars or room ambi­ance on percussion.