User Manual
7
GeneralTips/Troubleshooting
Mute Function
An important feature of a studio-grade AD/DA converter is the ability to
instantly mute itself, if errors occur in the digital data stream. This can happen
very easily in practice - for example, when more than one digital device in the
system is accidently operated as master. Such errors are especially
hazardous to high-quality monitor loudspeakers, which can quickly be
destroyed by the resulting high-energy impulses.
The A16 Ultra
A16 Ultra
mutes its inputs upon detecting a digital carrier signal with an
incorrect sample rate. On the other hand, an input signal from an
unsynchronized source does not cause muting, and the signal is allowed to go
through. Because the works with any phase at its inputs, clicks and
pops occur only occasionally, when an ''extra’' sample is inserted or when one
is left out. This can occur, if the A16 Ultra and the computer to which it is
connected are both operating as sync master.
AIl of the LEDs associated with the button are
s. indicates that the sync source signal is of good quality and that
the high-jitter-tolerance / low-jitter PLL is locked to the sync signal. , on the
other hand, generally indicates a problem with the digital connections.
Synchronization dual-color
LED Green
Red
8
S-MUX
The ADAT signal, as specified by Alesis, is defined only for sample rates
between roughly and . In order to permit the transfer of 96 kHz
data streams via the optical cable, a transfer format with the name S-MUX was
developed, in which the eight channels of a standard ADAT interface are used
as four pairs, each of which can transfer one channel at the higher sample rate.
Unfortunately, the fact that an ADAT signal is being used in S-MUX mode
cannot be ascertained from the signal itself. This means that this mode must
be selected deliberately and manually by the user.
37 kHz 50 kHz
Inappropriate S-MUX activation can result in the generation of unwanted high-
frequency signals. S-MUX is therefore always automatically switched off
whenever the sync source or the sync frequency is changed.
What happens if the transfer mode and the sample rate is chosen
incorrectly?
- Normal source (i.e. 44.1 kHz) with A16 Ultra S-MUX 88.2 kHz:
Pairs of channels get ''mixed'' and image frequencies are produced in the
range (or ). These higher frequencies generally inaudible
- could quietly cause overheating damage to the high-frequency drivers of a
monitor system.
22-44 kHz 24-48 kHz
S-MUX source (i.e. 96 kHz) with A16 Ultra normal 48 kHz:
Each single signal is ''spread'' across two channels. Frequencies which above
( ) will be imaged into the audible spectrum (this is normally
referred to as aliasing). This effect is rarely audible within most of the audio
material, as the high frequency content normally is minimal.
24 kHz or 22 kHz