TA Hifi PULSAR CD-1220 R

The CD 1220 R employs a fully programmable signal processor (DSP) which can process digital signals in any conceivable way. For this reason it produces better oversampling characteristics than are possible otherwise using ready-made commercially available chips. Commercial oversampling filters are invariably designed to produce as flat a frequency response as possible, without taking into account time-related characteristics, i.e. those concerning transient response. The inevitable result is long pre- and post-echoes which can seriously distort the listener's perception of the music - especially where peak signals are concerned.

Different types of filter - known as polynomial filters - are now available which exhibit perfect transient signal handling. Unfortunately these filters show a slight drop in treble response at 20 kHz. The CD 1220 R makes use of one class of these filters - BEZIER polynomial filters - combined with an IIR filter in a three-stage oversampling process. The result is a filter which produces no pre-echoes. The human ear is particularly sensitive to pre-echoes for two reasons: on the one hand they never occur at all under natural conditions, and on the other they are not masked by the main signal - as is the case with post-echoes. This filter also has a flat frequency response, which is a considerable improvement over other polynomial filters (e.g. cubic splines).

Since filters of such refinement cannot be purchased ready-made, the CD 1220 R utilises a digital signal processor to fulfil this purpose. Since the signal processor is completely programmable the CD 1220 R is not tied to a particular filter type. As a result we have been able to give the machine a total of five different filter types, each with a different sound character, ranging from the classic long
FIR filter to the BEZIER filter, with short FIR filters between the two. Each of these filters can be activated directly via its own button on the machine's front panel.

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