2.0 OPERATIONAL CHARACTERISTICS
Special features...
Main and Sidechain
audio paths
A and B noise
reduction
The Aphex Aural Exciter Type III, Model 250, is the latest generation, fully -
professional Aural Exciter, loaded with powerful new processing features
and improved circuitry. The dual-channel Type III adds thrilling new
dimensions to Aural Excitement. Noise and distortion are virtually elimi
nated in the Type III circuitry, with new special features that make enhance
ment possible and actually erase noise from noisy sources. The Model 250 is
the third successor to the original Aphex Aural Exciter that started an audio
revolution back in 1975.
2.1 N ew Features in the M odel 250
The Aphex Type III Aural Exciter utilizes a patented audio process that will
recreate and restore missing harmonics. These harmonics are musically and
dynamically related to the original sound. When added, they restore natural
brightness, clarity and presence, and can actually extend audio bandwidth.
These harmonics are so low in level, however, they add little power to the
signal. Unlike an equalizer or other "brightness enhancers," which can only
boost high frequencies, the Type III Aural Exciter extends the high frequen
cies. It is a single-ended process that can be applied at any point in an audio
chain, and needs no decoding.
2.1.1 Two Audio Paths
The Type III Aural Exciter process consists of two audio paths, the main path
and the process side-chain path. The main path transparently conveys the
audio signal directly from the input stage to the output stage, maintaining
unity gain with wide dynamic range. The side-chain path contains all of the
Aural Exciter processing circuits and receives audio from the input stage. A
mixing circuit in the main path allows the sidechain output signal to be
mixed with the main signal. You adjust the amount of MIX to set the
strength of the effect.
2.1.2 Two Noise Reduction Modes
Additional new design features include two modes of noise reduction. Mode
A and Mode B, for sound enhancement without adding to the noise floor of
reasonably noise free sources. It can also enhance the brightness, detail and
clarity of seriously noisy audio sources while, at the same time, erasing much
of the original noise.
Mode A operates as a linear sidechain expander with variable threshold. The
expansion ratio of 2.5-to-l permits the sidechain MIX to follow the signal
level below threshold. When the higher frequencies of the input signal
drop below threshold, the MIX will drop at a proportional 2.5 to-1 ratio. In
this way, the original signal-to-noise is not affected even with a great deal of
enhancement.
Operational Characteristics
2-1
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