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Design Overview

Spectral Introduces

the HDCD 'Long Filter'

Decoding Technology

Now Spectral introduces the next generation of high-

performance filters. The new HDCD 'Long Filter'

technology takes digital playback to the next level

with the fastest sampling and most filter poles ever

assembled for digital audio playback. With new soft-

ware designed to run on todays most powerful 32 bit

processors, the Spectral 'Long Filter' utilizes floating-

point math for higher accuracy and features the pro-

cessing power of eight PMD-200s for vastly faster

calculations.

The Spectral HDCD 'Long Filter' is Todays

Most Advanced 16 Bit Decoding Software

The original HDCD filter correction strategy was

designed by 'Pflash' Pflaumer around Keith Johnson's

psycho acoustic models and implemented in the fastest

processors of the mid-1990s. The vastly higher samp-

ling rate and memory storage of the 'Long Filter'

make possible a much more extended version of Keith

Johnson's sonic model and more precise corrections.

These advanced correction algorithms improve timing

accuracy at all frequencies we hear. By anticipating

time shift and producing an opposing response pro-

gram, time dispersion is greatly corrected adding the

third dimension to filter math that reveals more life,

sparkle and dimensionality.

In a day and age of maturing digital audio technology,

cost reduction and component integration, ( think of

todays premium sigma-delta type DAC chips with

self-contained filter programs which lower costs and

reduce chip counts ) there is the unexamined belief

that digital audio filter programs have attained a high

degree of accuracy and refinement, especially in high-

end and studio applications. The unfortunate truth is,

virtually all digital audio products from mid-fi to the

most expensive high-end luxury and prosound units all

use most of the same commodity filter technology.

In the SDR-4000 CD Processor, Keith Johnson set out

to redefine the performance of the 16 bit compact disc

with the most advanced components and circuit topol-

ogies yet devised for CD reproduction. At the same

time, a parallel effort by Keith Johnson and Michael

'Pflash' Pflaumer was launched to develop a very

advanced digital playback filter based on the sophist-

icated Pacific Microsonics HDCD software.

Since its introduction in 1995 the original PMD-200

HDCD digital filter software has been the choice of

high-end digital audio designers for their most ambit-

ious processors and players. This was no accident.

Digital designers in most high-end companies recog-

nised the unrivaled performance of the PMD-200.

Although conventional digital filter designs appear in

every type of digital product today, custom digital

audio filters are not designed every day, particularly

to ultimate audio standards. The Microsonics discrete

HDCD filter chip gave high-end designers the most

powerful filter processor with the most sophisticated

algorithms yet developed for 16 bit digital playback.

Spectral Audio, Inc.

442 Oakmead Parkway

Sunnyvale, California 94086

408.738.8521 Fax: 408.738.8524

COMMITMENT TO EXCELLENCE IN MUSIC REPRODUCTION

All files are copyright 2008 by Spectral Audio, Inc.

>

Since the digital audio chip industry has moved on to

standardized, prepackaged filter programs, high-end

component designers are left with few options but to

hope for the best and assume these packaged filters

are more than "good enough".

The Spectral 'Long Filter' Makes Compact Disc

a High-Resolution Medium

This is not the first time we have encountered the

"perfect sound forever" assumptions in the attitudes

of digital audio designers. After evaluating the per-

formance of the most ambitious DAC/filter programs

available under dynamic recording and playback con-

ditions, Spectral engineers found filter sonics to be

seriously compromised even for the most non-critical

applications. Clearly, filter design compromises are

holding back digital sound quality in most digital

audio products. The Spectral HDCD 'Long Filter' is

our solution for this vital link in the digital decoding

chain and argueably the first significant step forward

in high-performance digital audio filter design in over

a decade. The Spectral HDCD 'Long Filter' makes

the compact disc a high-resolution medium.

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COMMITMENT TO EXCELLENCE IN MUSIC REPRODUCTION

All files are copyright 2008 by Spectral Audio, Inc.

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