User Guide

dCS Purcell User Manual Manual for Software Issue 2.2x
dCS Ltd September 2004
Manual filename: Purcell Manual v2.2x.doc Page 3 email: [e-mail]
English version web-site: www.dcsltd.co.uk
PRODUCT OVERVIEW
Developed from our highly successful and acclaimed dCS 972 professional
DDC, the dCS Purcell is the first high precision Digital to Digital Converter (DDC)
designed specifically for audiophile use. It is used to increase the sample rate
and/or wordlength of the output from domestic linear PCM digital audio sources,
such as CD and DVD players, up to a maximum sample rate of 192kS/s and a
maximum wordlength of 24 bits. This is achieved using extremely powerful and
accurate digital interpolation filters, which introduce negligible levels of
distortion.
When decoded by an appropriate DAC, the upsampled signal from the Purcell
shows improved dynamics, more dimensional stereo imaging in terms of both
width and depth, more accurate bass, better resolution of fine detail and a more
relaxed and natural presentation. In this context an "appropriate DAC", means
one that can accept sample rates of up to 96kS/s and input word lengths of at
least 20 bits and preferably 24 bits. The greatest improvement will be achieved
when using the dCS Elgar Plus 24/192-DSD DAC. The Elgar Plus, because of its
proprietary dCS Ring DAC technology, has the finest linearity of any consumer
DAC currently available and is able to accept input sample rates up to 192kS/s.
The most common use for the Purcell is to upsample the 16 bit 44.1kS/s digital
output from a CD transport or player to either 24 bit 96kS/s, 24 bit 192kS/s or
DSD. We have carried out listening tests with the dCS Elgar Plus 24/192-DSD
DAC using CDs manufactured from 24/96 digital masters and have found that
upsampling reveals information that is present in the master source, but which
is not audible when the CD is played back normally. Upsampling cannot
increase the amount of information in a signal and the exact mechanism behind
the perceived sonic improvements is currently not entirely clear. We are
continuing our research into this subject.
Units fitted with the IEEE 1394 interface can upsample the source data to DSD
format (a single bit data stream, sampled at 2.822MS/s), for conversion to extra
wide-band audio by a dCS Elgar Plus or Delius DAC.
Purcell uses the same digital processing engine running the same DSP code as
the dCS 972 / 974 and they are sonically identical. The extensive use of
programmable logic makes the Purcell extremely flexible and easy to upgrade.