Manual

1.12
Operation Manual
© 2016 Prism Media Products Ltd
Revision 1.01Prism Sound Callia
4 Callia hardware
This section describes in detail the capabilities of the Callia hardware.
4.1 Front panel
Callia's front panel contains a number of controls and indicators; from left to right:
· Source selection indicators to show which digital audio source is currently selected, and whether
source selection is in automatic or manual mode;
· Format indicators to show the current audio format of the selected source;
· Line volume control which adjusts the volume of the analogue line outputs;
· Headphone jack, with its own volume control;
· Standby/source button which is used for manual source selection and to switch the unit in and out
of standby mode.
Source selection
In automatic source selection mode (indicated by the 'Auto' LED being lit) sources are selected
automatically according to sensing of valid audio at the inputs. In automatic mode, the current source
remains selected until it is silent (or otherwise absent) for more than four seconds whilst another input
is playing - in that case the other input is selected. The four second delay is to prevent spurious
switching during silences between tracks.
Alternatively, in manual source selection mode (indicated by the 'Auto' LED being unlit) sources are
manually selected by repeatedly pressing the standby/source button (on the right of the front panel),
which causes the selection to rotate from left to right around the three sources. Note that presses
must be short - holding the button in for more than one second will switch the unit into standby mode
(see below). Actually, the source can be manually overridden in automatic mode too (but only from
those sources which are present and playing) by pressing the standby/source button.
Toggling between automatic and manual mode is achieved by pressing the standby/source button in
quick succession so as to bring the selection back to its original position.
Audio format indication
The sample rate of a PCM input is shown by a combination of the '44k1' and '48k' LEDs and the 'x2'
and 'x4' LEDs. For example, a source sampled at 44.1kHz is indicated by the '44k1' LED alone,
whereas a 96kHz source is indicated by the '48k' and 'x2' LEDs in combination, and a 352.8kHz
source would cause the '44k1', 'x2' and 'x4' LEDs all to be lit. If a PCM source has 16 active bits (or
fewer), the '24b' LED is unlit, whereas it is lit blue to indicate a wordlength between 16 and 24 bits, or
pink to indicate a wordlength greater than 24 bits (the latter is only possible in USB source mode).
A DSD64 source (a 2.8224MHz bitstream) is indicated by the 'DSD' LED on its own, whereas a
DSD128 source (a 5.6448MHz bitstream) is indicated by the 'DSD' and 'x2' LEDs together. Note that
DSD sources are detected by the presence of DoP (DSD-over-PCM) flags, and that DSD128 is only
possible in USB source mode. Callia can accept DSD sources which are at multiples of 48kHz as