API audio 529 operation manual

529 Stereo Compressor

OPERATOR’S MANUAL

Written for Automated Processes Incorporated

by Daniel Pfeifer 2018

8301 Patuxent Range Road

Jessup, MD 20794 USA

301-776-7879

http://www.apiaudio.com

Table of Contents

Introduction ..................................................................................... 2

Features ................................................................................................. 2

Overview .......................................................................................... 3

Compressor Controls ........................................................................ 3

THRESHold ............................................................................................. 3

RATIO ..................................................................................................... 4

ATTACK ................................................................................................... 4

RELEASE ................................................................................................. 4

MAKE UP GAIN ....................................................................................... 4

Compressor TYPE ............................................................................. 5

NEW (Feed-Forward) .............................................................................. 5

OLD (Feed-back) .................................................................................... 5

Compression KNEE ........................................................................... 6

HARD KNEE Compression ....................................................................... 6

MEDIUM KNEE Compression ................................................................... 7

SOFT KNEE Compression ........................................................................ 7

THRUST® ........................................................................................... 8

THRUST® NORMal .................................................................................... 8

THRUST® MEDium ................................................................................... 9

THRUST® LOUD ....................................................................................... 9

Compressor Bypass (OUT) .............................................................. 10

Meters ............................................................................................ 10

Stereo VU Meter ................................................................................... 10

GR (Gain Reduction) Meter ................................................................... 11

Introduction

The new 529 Stereo Compressor combines the unmistakable sound of API’s compression technology with the convenience and popularity of the API 500 Series format.

Carefully designed to deliver a wide range of compression options, the 529 delivers warmth, clarity and punch, whether used for subtle adjustments or heavy compression effects.

Based on the unprecedented success of the 2500, the 529 takes many of the features and controls from API's famous stereo bus compressor and puts them into the first dual slot 500 series module from API. Using API's discrete op-amps and transformer technology, the 529 delivers the legendary analog sound of API.

The 529 is a two-channel, stereo-linked dynamic processor designed for stereo program bus compression and compression of any stereo audio source. The audio input signals from both channels are combined in a true-RMS power summing fashion to create the compression control signal for the detection path. Then, the resulting compression signal is applied evenly to both channels for proper balance. All front panel settings control both channels simultaneously.

This stereo compressor features API's patented

THRUST

an OLD/NEW switch that lets you choose between classic and modern compression characteristics: OLD for vintage-style feedback compression and NEW for today's more common feed-forward compression. The 3-position KNEE switch adjusts the shape of the curve at the onset of compression for an "over-easy" type compression resulting in a very natural, uncompressed sound or a typical sharp knee type that lends itself to a much more severe limiting effect.

The Auto MAKE UP gain function lets you adjust ratio and threshold controls without affecting the output level. Alternately MAKE UP gain can be set manually.

Features

circuitry for a punchy low end, along with

 Continuously variable 31-position detented controls for Gain, Threshold, Ratio, Attack & Release  Stereo 10-segment LED VU meters show selectable Input or Output levels  10-segment LED Gain Reduction meter  “Over Threshold” LED illuminates when input audio cross the set THRESHold  Patented THRUST  3 selectable compressor curve KNEE settings  Selectable NEW or OLD switch for feed-forward or feed-back operation  Selectable automatic or manually variable compressor make-up gain  Full hard-wired relay bypass  Audio circuit uses 2510 and 2520 discrete op amps with transformer output  2-space 500 Series insta llation

filter for frequency dependent side chain control

529 Stereo Compressor API

Overview

The 529 Compressor provides a comprehensive suite of controls:

• THRESHold: The level at which compression begins (+10dB to -20dB)

• Threshold LED: Indicates when the input audio crosses the selected THRESHold level

• RATIO: The amount of compression applied after threshold (1.5:1 to ∞:1)

• ATTACK: The time it takes for the compressor to respond (1 to 50 m/sec)

• RELEASE: The time it takes the compressor to return to unity gain (.05 to 4 seconds)

• METER: Selects OUTPUT or INPUT as the source for the stereo VU meter

• VU (Stereo VU Meter): Stereo 10-segment LED VU meter (selectable OUTPUT or INPUT)

• GR (Gain Reduction) Meter: 10-segment LED gain reduction meter

• MAKE UP: Selects AUTOmatic or MANUAL MAKE UP gain

• GAIN: Manual MAKE Up gain control (0dB to +24dB of output gain when MANUAL is engaged)

• TYPE: NEW (feed-forward) or OLD (feedback) detection path topology

• KNEE: The characteristic of the response curve at the onset of compression.

• THRUST®: Patented circuit that inserts a filter before the RMS detector

• OUT: Toggles to swich gain reduction in or out or engages hard bypass

Compressor Controls

THRESHold

THRESHold: Sets the level at which compression begins

• Continuously variable range between +10dB and -20dB

• Detented rotary pot for easy recall

Threshold LED: Illuminates when the input audio crosses the level set by the THRESH control

• Illuminates in red when active

529 Stereo Compressor API

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