DSPXmini-FM operational manual V1.2
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mum setting of a balance of the two.
The peak attack time should be set to the desired attack time required from that limiter. The range is 1-10 which
corresponds to 1 to 200mS on an exponential scale. The peak decay time should be set to the desired peak
decay time required for transients. The range is 1-10 which corresponds to a decay time of 10 to 1000mS.
The average attack time is perhaps the most important control in the dual time constant detector as it sets the
balance between peak and average energy in the detector. With smaller numbers more energy is transferred
into the average circuit and a higher platform level is created so more time will be spent releasing at the slower
average rate. Higher numbers offer slower attack times for the averaging part of the detector and this has the
effect of lowering the average platform level and allowing the peak part of the circuit to dominate with its faster
release times.
The average decay time can usually be viewed as the nominal release time of the detector, similar to a standard
single time constant limiters release time.
To recap, the peak attack time and average decay time play the same sort of role as that of a standard con-
ventional single time constant based limiter. The peak decay time sets the decay time for fast usually inaudible
transients and the average attack time sets the ratio of peak to average control and defines the position of the
platform that the peak circuit releases to.
The mixer
The post limiters mixer in the DSPXmini-FM is not strictly a mixer but a band output level control where small
EQ changes can be made.
Be careful when making large EQ changes at this stage because there is no peak control prior to the clipping
system. It is easy to overload the clipping stages by setting these controls all to large positive values.
The control range for each band of +/- dB is purposely restricted for the above reasons.
Bass clipping
Most competent processors have a bass-clipper prior to the final clipper. The purpose of the bass-clipper is to
keep low frequency energy to a pre-determined level to allow for the summation of the other bands. Without the
bass-clipper the bass signal can push the mid and HF audio waveforms into the final clipper creating audible IM
distortion, the worst type of distortion. By restricting the bass to a certain level the mid and HF energy has its
own reserved space in the summated waveform and we reduce the likelihood of bass generated IM distortion.
Peak time constants dominating control due to
a very high setting of average attack
Peak time constants dominating to a lesser
degree due to high setting of average attack
Peak time constants dominating to a much
lesser degree due to a lower setting of average
attack
Limiter control signals response to tone bursts
Peak time constants dominating control due to
a very high setting of average attack
Peak time constants dominating to a lesser
degree due to a high setting of average attack
Peak time constants dominating to a much
lesser degree due to a lower setting of average
attack
Limiter control signals response to program material
