4
Sample Rate
S. RAT is the default display mode and displays the sampling rate of the digital input signal
with 3½ digit resolution. If the sample rate rounds to between the 3 displayed digits, a decimal
point is added to the right of the third digit; 44.056kHz = 44.0., 176.4kHz = 176.. Adjusting
volume or balance in S. RAT display mode momentarily displays volume or balance. When
an MQA Core decoded input signal is present, MQA is displayed instead of the sampling rate.
Digital Filter Selection
For the best possible audio fidelity the default interpolation filter, Filter 1 (1.16 or 1.24)
should be used. Filter 2 (2.16 or 2.24) is a minimum phase type with minimum pre-ringing.
Digital interpolation filters 1 or 2 can be selected by selecting the Filter display mode and
pushing the front panel + or − buttons. The filter selection made for each sampling rate is
stored independently in memory.
At 44.1kHz only (the sampling rate of Red Book standard compatible HDCD encoded CD’s)
there are 16-bit LSB and 24-bit LSB HDCD code detect versions of each filter, e.g. 1.16 &
1.24. The main difference between the .16 and .24 versions of the 44.1kHz filters is the bit the
filter looks for HDCD LSB code in. In all other ways, except for peak output level, they are
identical. (See HDCD below). All other sampling rates have .24 24-bit LSB HDCD code detect
versions only.
MQA
When a valid MQA Core decoded signal is present on the selected digital input, MQA is
displayed on the 3 digit LED display instead of the input signal sample rate and MQA
Rendering is performed. Streaming applications like Tidal should NOT be set to assthrough
MQA which turns off MQA Core decoding that is required for MQA Rendering. Momentarily
pushing the MOD button on the remote control temporarily shows the MQA original sample
rate on the 3 digit LED display.
HDCD
The HDCD LED lights when HDCD code is detected in the LSB of the digital input signal and
HDCD decoding is automatically performed. With 44.1kHz sampling rate signals 16-bit LSB
HDCD code is detected by default, e.g. filter 1.16. 24 bit LSB, 44.1kHz HDCD code detection
can be selected in Filter display mode, e.g. filter 1.24. At sampling rates other than 44.1kHz
only 24 bit LSB HDCD code is detected and only 24-bit LSB HDCD code detect filters ending
in .24 are provided. Note: Selecting 24 bit LSB HDCD code detection at 44.1kHz turns off
HDCD amplitude decoding and increases output level by 6dB.
Display Dim
ushing the Dim button on the remote control or front panel adjusts the display brightness.
Power On/Off Sequence
If the analog signal outputs of the Alpha DAC Reference Series 3 are connected directly to
power amplifiers it should be powered on for 15 seconds or longer before the power amplifiers
are powered on. Before disconnecting power to the Alpha DAC Reference Series 3 the power
amplifiers should be powered off first. The Alpha DAC Reference Series 3 is designed to
power on and off without producing output noises that could damage power amplifiers or
loudspeakers. However, this power on and off sequence should be followed for maximum
protection of associated components.
Upgrading Firmware
Alpha DAC Reference Series 3 firmware is upgradeable by playing a special encrypted WAV
file through any digital signal input. When the Alpha DAC Reference Series 3 is powered on
the current firmware version is displayed.
