Digital Audio Server (DAS) Overview
The DAS is a true reference designed for the discerning Audiophile. The DAS has an extremely low noise
floor with greater spacial refinement, dynamic accuracy and fine detail retrieval than any other audio server
on the market.
The DAS has an integrated pre-amp and is capable of driving a power amplifier directly, thus replacing up to
4 separate units (e.g. CD transport, DAC, pre-amp, PSUs) and interconnects.
The CAAS DAS has been designed to produce the highest audio quality possible. Within the pre-amp
section, this has been achieved through capturing the ideal qualities of a passive pre-amplifier without the
source loading and load driving capability issues normally associated with a passive pre-amplifier. Within the
Digital Audio Server section, this has been achieved through our bespoke 176.4k samples per second up-
converting parallel DACs and ultra low jitter clock, allowing near perfect data re-clocking and bit perfect I2S
digital signal transfer.
The DAS internal pre-amp consists of a bespoke switched resistor volume control. The front panel volume
knob simply provides a reference voltage to the internal analogue to digital converter (ADC) which in turn
controls a bank of high quality silver contact relays that switch different configurations of high quality metal
film resistors to produce attenuation levels between -50dB and 0dB in 128 discrete steps. Although this is a
more complex system than the standard audio potentiometer, the sonic purity far exceeds any audiophile
potentiometer on the market, irrespective of price and is therefore essential in producing the best sound
reproduction possible.
The bespoke volume control feeds a single JFET gain stage incarnation of CAAS Audio's proprietary “CSD”
amplifier. In the DAS this stage is configured as a DC coupled, zero feedback current buffer offering
extremely low THD, IMD and TIM and the cable and power amplifier drive capabilities that passive pre-
amplifiers lack, thus offering the most open, natural and transparent sound possible.
The DAS is an extremely versatile audio server and pre-amplifier with two analogue audio inputs, a single
S/PDIF input and a USB input. The DAS also has networking capability.
The DAS is fitted with a Raspberry PI micro computer and a bespoke ultra low jitter re-clocking system that
up-samples digital data to 176.4k samples per second and feeds a parallel arrangement of 16 bit R-2R
DACs. The DAS is fitted with eight dedicated discrete regulated power supplies for both Left and Right
analogue channels and seven separate regulated supplies for the digital sections.
The DAS is primarily an Audio Server and the best performance will be achieved when files are accessed
from a USB pen or HDD. Alternatively digital audio can be streamed from either a NAS, a PC, a tablet or a
smart phone over the LAN connection. A CD transport or other devices can be connected to the DAS
S/PDIF input, however this input bypasses our bespoke low jitter re-clocking system and therefore is not the
primary input.
All music files and data can be accessed through the on screen interface once the DAS has been connected
to a TV or monitor (though HDMI). If the TV has HDMI CEC then all the DAS functions can be accessed
through the TV remote, alternatively the functionality can be accessed through a LAN interface, tablet or
smart phone.
The power supply is a key component in achieving the maximum performance from the audio sections and
for this reason the DAS is fitted with a high specification mains filter and two separate transformers, one for
the analogue sections and one for the digital sections.
The DAS has analogue DC coupling from input to output and a short signal path.
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