Specifications

Processing Structure
14
Mixer
The six bands are 'virtually' mixed together at this stage. In truth, the six bands have become three. The
three bands are fed off into the two peak processing paths.
Distortion controlled clippers (PEAK CONTROL PATH 1)
The DSPXtreme clipping algorithms peak limit (clip) and linear phase filter the audio in three bands for maxi-
mum distortion control before being fed to the final clipper stages.
Look-ahead limiter (PEAK CONTROL PATH 2)
The DSPXtreme look-ahead limiter is one of the most sophisticated available in a broadcast processor.
Processing is performed in three bands for maximum transparency and clarity. A cut shelving filter is provided
to compensate for the effect of pre-emphasis when the DSPXtreme is used to process FM signals at the
same time.
Delay
The DSPXtreme has an adjustable time delay for the MPX output that can be optionally selected for the ana-
log and digital outputs as well. Delay should only be used if you're simulcasting analog FM and HD Radio
(IBOC) and want synchronisation between these two transmission for perfect blends in the receiver. Separate
menu allows adjustment of the delay up to 11 seconds, with coarse, medium and sample-accurate fine con-
trol. If you're not using HD Radio and transmitting only analog FM, leave the delay controls at 0 settings.
Output selection, processing and routing
The DSPXtreme allows the user to select where each processing path is routed to and provides output level
controls. There are four choices for digital outputs to choose from - FM path, delayed FM path, DR path and
monitor. For analog outputs the options are FM path, delayed FM path, same as AES2 and monitor.
The monitor output is a lower latency (delay) path that bypasses the final clipper stages and reduces delay
by more than 4 ms. This can be used to help with talent (DJ's) who can not get to grips with the delay of the
main processing path. This output if selected should only be used as a studio monitor signal and should not
be used ‘on the air’ as the peak clipping stage in the monitor processing path is not over-sampled or anti-ali-
ased.
A de-emphasis option is provided on both the analogue and digital outputs. The digital output sample rate
can also be configured to a variety of settings.
The analog and MPX outputs will be affected by the ITU limiter, if it is engaged. The purpose of this limiter is
to comply with the ITU BS.412 standard. The standard calls for limiting of the power of the composite signal
being broadcast. When activated, the ITU limiter will drastically reduce the loudness of your signal.
Stereo encoder
The DSPXtreme's DSP stereo encoder takes its inputs from the FM path of peak processing. The audio fed
to the stereo encoder does not pass through any de-emphasis circuits and is always delayed by the amount
set in the Delay menu. 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.