A/D Conversion Of Analog Tape Recordings - Pacific Microsonics HDCD Model Two User Manual

Setup & Operation

A/D Conversion of Analog Tape Recordings

To obtain the very best possible quality when converting analog master tapes to digital
masters using the Model Two, the following steps are recommended.
1. The outputs of the analog machine should be "hot rodded" directly to the analog
inputs of the Model Two using minimum length runs of high quality cable, without
going through a console or patch bay. Record levels should be set using only the
analog input attenuator on the Model Two and the output level trim on the analog
machine. If EQ or other processing of the analog signal is necessary, a high quality
analog EQ or processing unit should be connected directly into the "hot rod" path
without using a patch bay. In some cases, where only simple treble EQ is required,
the play EQ on the analog machine can be adjusted, eliminating the need for an
outboard EQ unit. The idea is to keep the analog signal path as short as possible.
2. The analog transfer should be made with the Model Two's A/D converter set to 24-
bit at the highest possible sampling rate. If the A/D conversion frequency is 44.1
or 48 kHz, one AES output can feed a 24-bit digital recorder while the other AES
output is fed to a 24-bit editing DAW. Thus, a 24-bit, 44.1 or 48 kHz archive
recording can be made at the same time the DAW is being loaded.
3. Digital processing in the workstation that involves level shifting, EQ etc. should be
carefully evaluated for sonic quality. High quality 24-bit editors, if set up correctly,
can sound quite neutral when used for assembling and sequencing segments, how-
ever level shifting, EQ, and other processing operations can sometimes create au-
dible distortions.
4. If the digital editor's level control doesn't sound sonically neutral, peak levels for
the HDCD 16-bit release master can be adjusted using the DSP Gain feature of the
Model Two, which has extremely low distortion. Set the Model Two to 24-bit digital
in, 16-bit digital out mode, using the DIG44-16 preset. Feed the 24-bit output of
the workstation to the Model Two, and use DSP Gain to adjust the 16-bit peak level,
which can be up to 6 dB above full scale if Peak Extend is used. (monitor HDCD
amplitude decoding should be turned alternately on and off while monitoring the
analog D/A output of the Model Two when setting levels using Peak Extend to hear
any Peak Extend limiting with undecoded playback.)
No digital processing, including any form of EQ, level shifting, dither, rounding or truncation
can be performed on HDCD encoded signals without losing the hidden LSB code that allows
HDCD filtering and decoding. However, cuts or rapid ( 100 ms) cross fades will not disrupt
playback filtering or decoding and are OK.
P A C I F I C
Rev. C - January 2002
Model Two HDCD
M I C R O S O N I C S
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34
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User's Manual
I N C .