Specifications

Prism Media Products Limited AD-2 Dual-rate A/D converter
Operation Manual
Issue 0.2 © Prism Media Products Limited
11 August 1998 Page 33 of 58
5. SYNCHRONIZATION MODES
In A-D mode, the AD-2 Dual-rate A/D converter can be operated as either a clock
master or a clock slave. This is determined by the setting of the ‘Sync Mode’ menu.
If the Sync Mode is set to ‘Int’, then the Main and Aux output rates are set to the rates
requested in their respective menus, and are referenced to the AD-2s internal precision
reference.
If the Sync Mode is set to ‘DI’, then an external reference sync is used. The type of
external sync to be used, and on which connector, is defined in the ‘D-D Mode Setup’
menu: this may be an AES3, AES-3id, IEC958 or an SDIF-2 wordclock reference.
An unusual feature of the AD-2 is that this reference may be at any standard rate (i.e.
32kHz, 44.1kHz, 48kHz, 88.2kHz or 96kHz) and the Main and Aux outputs will be
locked to it precisely, whether or not they are set to sample at the same rate as the
reference. For example, a house sync at 48kHz may be used to synchronize an AD-2
producing simultaneous 44.1kHz and 96kHz outputs.
Alternatively, if the Main or Aux path is set to ‘=DI’ rather than having a particular
sampling rate specified, then that output path will sample at exactly the same rate as
the external reference. If an AES3 reference sync is selected and is designated as
‘Split96', then the sample rate of an output path following DI is set to twice the incoming
AES3 frame rate (i.e. 88.2kHz or 96kHz).
In D-D mode, the AD-2 Dual-rate A/D converter can similarly be operated as either a
clock master or a clock slave as determined by the setting of the ‘Sync Mode’ menu.
Normally, D-D Mode operation will be in external (’DI’) mode, where the AD-2 is locked
to the incoming digital audio signal (as specified in the ‘D-D Mode Setup’ menu). This
does not mean that the Main and Aux path outputs must necessarily be at the same rate
as the digital input - they may be specified to produce a different, sample-rate-
converted output rate - but in any case their sampling frequency will bear a fixed
relationship to the incoming digital audio signal. Each of the Main or Aux outputs can be
precisely fixed to the incoming data rate by either selecting the same output rate for
that path as the current input rate, or by selecting the rate as ‘=DI’ to make the path
follow the rate of the incoming data, even if it changes.
If the Sync Mode is set to ‘Int’ in D-D Mode, then the AD-2 acts as a clock master: i.e. it
determines its output data rates from its high-precision internal clock, even though it
must accept its digital input data at the correct sampling rate (or, actually, at a standard
rate in fixed relationship to its output rate, since it may be rate-converting). It is
therefore essential that the sourcing equipment is locked to one of the outputs of the
AD-2 if correct interfacing is to be achieved.