Introduction; Features - API 2500 Operator's Manual

1.0 Introduction

To commemorate our 50
community, API has produced the 50th Anniversary Edition of the API 2500 Stereo Bus Compressor.
The 2500 Bus Compressor is API's flagship compressor and the 50
unique features to this highly-valued unit. These unique features include flexible output mix blending,
LED gain reduction meters, premium VU meters, and a 2ru, gold-faced chassis. A limited run of only
fifty 50 th Anniversary Edition 2500 compressors will be produced, so each unit is uniquely identified as
one of this exclusive class.
The 50th Anniversary Edition of the API 2500 Stereo Bus Compressor provides the unmistakable sound
of API's compression technology combined with unmatched parametric control. The result is one of
the world's best sounding and versatile stereo bus compressors that's capable of handling an infinite
number of production applications. Carefully designed to deliver a wide range of compression options
and features not found on the standard 2500, the 50th Anniversary Edition of the 2500 delivers
warmth, clarity and punch, whether used for subtle adjustments or heavy compression effects.

1.1 Features

• Limited 50
•
• Patented
• 3 selectable compressor curve KNEE settings
• Selectable NEW or OLD type switch for feed-forward or feed-back operation
• Preset or variable release time control
• Variable Left/Right link with peak and RMS control voltage filters
• Selectable automatic or manually variable make-up gain
• Variable input-output blending for onboard crossfaded or parallel compression
• Audio circuit uses 2510 and 2520 discrete op amps with transformer output
• Premium stereo VU meters show selectable input or output
• 10-segment stereo gain reduction meter
• Full hard-wired relay bypass
• Commemorative serial number plate
The 50th Anniversary 2500 has several unique features that will allow you to tailor the sound of the
compression in many different directions.
THRUST
The patented
consoles, as well as the Pro-6 Input Strip. This circuit places a filter in front of the RMS detector, with
a slope of 10dB per decade, which is the inverse of the pink noise energy curve. In acoustics, the
pink noise curve is used to equalize energy vs. frequency over the audio spectrum, as sound requires
more low frequency energy than high frequency energy to sound correct to your ear.
equipment, a "LOUDNESS" contour is used to equalize the music at lower levels so it sounds correct.
Even with this curve, there is still a substantial amount of low frequency information compared to high
frequency information in the audio signal path. When that signal is fed into an RMS detector, the
detector will process the signal into a DC control voltage based on those louder low frequencies,
resulting in a control voltage that favors the low frequencies of the signal, causing pumping and a loss
50 th Anniversary 2500 Bus Compressor
th year of providing high-quality audio equipment to the professional
th Anniversary Edition: Only 50 units built
"Over Threshold" LED illuminates when input audio crosses the set threshold
THRUST
® filter with 3 settings for frequency dependent side chain control
® feature has been used for many years in the famed ATI Paragon and Paragon II
th Anniversary Edition adds a few
6
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