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API 235L Noise Gate/Expander (8)
Automated Processes Inc.

235L Noise Gate/Expander The basic concept of the 235L is a very fast, good sounding gate with the ability to expand as well. Many comments about the 235L are centered around the unusually fast opening without loosing any part of the sound and the familiar API tone.

Module Specifications:

Frequency Response: +.2 @ 10Hz (+14deg), 0 @ 20Hz, 0 @ 20KHz (-14 deg), -.5 @ 100KHz
Noise Gate Closed: -102 dBu, Unweighted Gate Open: -90 dBu UnWeighted.
Distortion: Gate Open: -40 dBu=.3%THD, -30=.1%, -20=.03%, -10=.01%, +4=.008%, +12=.01%, +28=.1%

Attack Time: Fast=10u/sec to trigger gate cycle, Norm=120u/sec to trigger gate cycle. (less than 1 cycle of 20KHz) (less than 1 cycle of 8KHz)
Fast attack, -80 to 0, 50% open in 170u/sec, 90% open in 1m/sec.
Fast attack, -20 to 0, 50% open in 100u/sec, 90% open in 800u/sec.
Normal attack, -20 to 0, 50% open in 25m/sec, 90% open in 50m/sec.
Fast attack, -10 to 0, 50% open in 5u/sec.
Normal attack, -10 to 0, 50% open in 11u/sec.
Attack time with 5KHz trigger frequency, lower frequencies yield faster open times. Gate is usually on it's way within the first 15% of the first cycle if the input signal.

Trigger range: -45dBu to +25dBu with 0dBu about 50% rotation of the THRESH pot.
Gate Depth: 0dB to -80dB, LOG scale with -9 about 50% rotation. This provides more control from 0 to -20dB.
Expander: 2:1 ratio from below threshold to the trigger threshold, then unity gain. Expander linearity better than 1.25dB error from -80dBu to +20dBu. Error is constant throughout entire gain range.
Release/Hold: The Release time or Hold time is selectable with the REL/HLD switch. Each provides 50m/sec to 3 sec of release or hold time.
Adjustments: (1) attack threshold scale trim pot. VCA is pre trimmed for distortion and offset. There is no audible thump when gate is triggered externally.
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