Audio engineering company ATC is introducing two new system components. The CD2 CD player and SIA2-100 2-channel integrated Amp/DAC are designed to work together, or individually to upgrade existing sources or amplifiers. They join a range of audio electronic products and loudspeaker systems designed and built in Stroud, mostly by hand, for studio and Hifi applications.

ATC believes that there is still mileage in the humble Compact Disc, now in its 36th year. Although many music lovers increasingly rely on file-based or streamed music systems, they also own large collections of CDs. In order to provide high quality playback for both mediums, ATC has decided to offer users the flexibility of a “stand alone” CD player rather than integrate a player within the SIA2-100.

ATC CD2 Stereo CD Player

The ATC CD2 Stereo CD Player provides a line-level stereo output on RCA phono sockets, together with true differential Left and Right outputs on XLR sockets. Digital S/PDIF Outputs are available on Optical Toslink and Coaxial outputs. Operation is through 5 push buttons on the front panel, which are duplicated on the ATC remote control handset supplied.

ATC SIA2-100 2-channel integrated Amp/DAC

The SIA2-100 integrated amplifier/DAC has been engineered to partner the CD2 as a compact music separates system, and all passive stereo loudspeaker pairs. It is a versatile one-box design for D/A conversion and pre/power amplification duties specified to generate 2 x 100W (continuous into 8 ohms). The SIA2-100 incorporates 2 pairs of stereo line level inputs on RCA phono sockets, together with a front panel mounted 3.5mm jack socket input, a digital SPDIF optical Toslink input, a digital SPDIF coaxial input on an RCA phono socket, and a USB digital audio input on a USB B socket. There is a single pair of stereo power amplifier outputs on 4mm binding posts, a stereo line level output on RCA phono sockets, and a front panel mounted headphone output on a 6.35mm/0.25″ jack socket. Input selection is achieved via a front panel push button, and output volume adjustment is via a precision Alps potentiometer. All SIA2-100 functions are duplicated on the ATC remote control handset supplied.

Both the CD2 and SIA2-100 chassis are constructed to be heavy, rigid and well damped with precision machined 12mm aluminium front panels finished in brushed and anodised ‘titanium’ silver.

Technical Information

In the place of a computer-type or slot-loading drive the CD2 uses the TEAC 5020A-AT transport, which has passed ATC’s rigorous tests  The DAC is from AKM operating in conjunction with an output filter stage comprising a digital filter and ATC’s own low-noise multiple feedback analogue filter. The CD2’s four gain stages, each comprising 11 discrete components, provide a “true” differential output for the left and right channels. The output stages are configured as unity gain complementary compound (Sziklai) pairs, biased in class A. The positive and negative drivers are arranged in parallel to ensure that signal delays and phase shifts on each side are similar.

ATC’s preference for distributed “local” power regulation and decoupling means that no fewer than 9 individually calibrated power regulators are deployed in the circuit design. The digital coax output uses a high performance isolation transformer to prevent possible hum loops if both audio and digital signals are connected to the same equipment. All PCB track lengths are as short as possible, and grounding and screening is applied.

Similarly rigorous measures are taken to reduce noise and distortion in the SIA2-100 integrated amplifier/DAC. Its power amplifiers use the circuit topology which has been revised and refined over the past 30 years for all ATC power amplifiers. Lateral Mosfets are deployed in a common source configuration to provide very low distortion together with a wide frequency response. A peak limiter is included to protect the loudspeaker drivers in the event of an overdrive.  To reduce intermodulation and cross-talk aberrations there are separate power supplies for the pre-amplifier and power amplifier sections.

ATC’s discrete analogue design and use of multiple local power supply regulators provides the optimum operational platform for the SIA2-100’s AKM onboard DAC and USB receiver. The USB input will handle PCM sample rates from 44.1 kHz to 384 kHz, with word lengths to 32 bits, and also decode DSD sources at 2.822 MHz (Single rate, DSD64), 5.644 MHz (Double rate, DSD128). All inputs, analogue and digital, achieve distortion figures below 0.001%.

Headphone Amplifier

The SIA2-100 incorporates a headphone amplifier and a 3.5mm auxiliary input with higher sensitivity, better suited to interfacing with portable audio devices.  Both of these circuits have been designed to deliver the lowest levels of noise and distortion.  The headphone amplifier is biased in class A and is specified to drive a range of headphones from 32 to 600 ohms.

Availability in April 2019. Typical retail prices (inc VAT): CD2, £1500, SIA2-100 £2500

ATC will be demonstrating the CD2 and SIA2-100 at the Bristol Hi Fi Show Fri 22nd – Sun 24th February, Room 102.

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