DSPXmini-FM operational manual V1.2
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The DSPXmini-FM broadcast audio processor is intended to be used for processing audio prior to broadcast on
FM .
Before we discuss the processing structure in full we would like to tell you a little about the final peak limiting
stage of the DSPXmini-FM. It employs distortion controlled clippers to limit the peaks of the signal. Distortion
controlled clipping is the best method for preserving as much high frequency energy as possible, important when
the high frequency loss characteristics of the FM broadcast de-emphasis curve is taking into account. Distortion
controlled clipping produces harmonic distortion which if used moderately can produce a sizzling bright sound
but can result in a ripping or tearing sound if used excessively (overdriven).
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Input selection and conditioning
The DSPXmini-FM offers the user input selection (analog or digital input) and pre-emphasis selection.
Bass enhancement
The DSPXmini-FM offers a bass enhancement via peaking filter that can be set to provide up to 6dB of gain
on one of four frequencies with a choice of Q's. This can be thought of as a simple bass parametric.
Xover
The DSPXmini-FM employs linear-phase time aligned digital FIR filtering to split the audio spectrum into
bands while maintaining sonic transparency.
Multi-band AGC
The DSPXmini-FM processes each band with RMS based levellers. Each bands gain control processing
function can be configured in different manners to provide different effects. Adjustable timing constants, drive
and gating afford the user with full control of this important re-equalisation stage of the processor.
Multi-band limiters
Each band has its own dynamic peak limiter. Multiple time constant based detectors are fully adjustable as
well as input drives.
Mixer
The four bands are 'virtually' mixed together at this stage, allowing overall EQ adjustment.
Bass clipper
The DSPXmini-FM peak limits (clips) and linear phase filters the low frequencies before being fed to the final
clipper stages.
Distortion controlled clipper
The DSPXmini-FM main clipper uses sophisticated algorithms to produce tightly peak controlled output and
maximum distortion control.
Stereo encoder
The DSPXmini-FM's DSP stereo encoder takes its inputs after peak processing. The stereo encoder is highly
over-sampled and offers superb stereo performance. A composite clipping function is provided for those who
wish to use it.
