Digital / Analog Converter
The D-70 is an advanced D/A (digital-to-analog) converter that can handle multiple 2-channel linear digital source signals. When 176.4 kHz or 192 kHz is used, 2 XLR inputs are used simultaneously to enable stable transmission. (AES 3 standard.)
* The Ultimate in Sound Reproduction Available from the Compact Disc Format
* Refined Digital Output Technology & Refined Asynchronous Memory Link
* Handles 24 bit Input with a Wide Range of Sampling Frequencies (32 to 192 kHz)
Advanced newly-developed Refined Digital Output Technology (RDOT)
The traditional belief is that the upper limit of human hearing is 20 kHz. In real life, however, information at frequencies over 20 kHz exists, and it is generally recognized that the presence of this information can significantly enhance the listening experience. However, when a CD is recorded, on account of the limitations of the sampling frequency, the audio upper limit is restricted to 20 kHz. RDOT provides a way to overcome this limitation and break the 20 kHz barrier, using the Fluency theory. The RDOT filtering utilized in the D-70 is equivalent to 24-bit/96 kHz input - a significant advance over the current 16-bit/44.1 kHz standard. When this new RDOT is employed, sources with up to 192 kHz sampling frequency, including the latest generation of audio discs, can be read. Using a higher frequency allows the "gaps" to be filled between the existing samples, effectively doubling the sampling frequency. The listener finds it easier to distinguish the sounds of individual instruments, even when many instruments are playing at the same time, and the quality of recorded reverberation is significantly improved, resulting in greater realism, and a much closer approach to a live performance.
TEAC's unique RAM link using new circuitry (Refined Asynchronous Memory Link)
In order to achieve an ideal jitter-free D/A converter, we have installed a full 128Mbits' worth of RAM Link buffer at the first stage of the DAC. The object is for the buffer to eliminate jitter completely, regardless of the amount of jitter or the frequency bandwidth. This results in an effective zero-error operation. The large amount of RAM in this buffer allows all incoming jitter to be absorbed completely in the buffer, and the data to be transferred, using the internal high-precision clock, to the next stage of the DAC. Key benefits of using a large RAM Link buffer:
1. Allows high bit-rate and high-frequency sampling
2. Extended continued playback is possible, and the high RAM
3. capacity makes it unnecessary to continually adjust the clock frequency. In order to produce a jitter-free stream, the optimum position for a buffer is immediately behind the digital filter. However, when oversampling takes place, and if there is a large amount of data to be buffered, then the RAM must be large enough to take account of this. On the D-70, both these aims have been achieved, with a buffer whose capacity is enough to handle the demands made on it
Servo-free direct clocking system
In the D-70, a servo-free direct clocking system is used, which comes close to the ideal of clock control. In systems where a clock other than the one derived from the digital audio signal is used, typically PLL (phase-locked loop) technology is used to keep the clock frequency as constant as possible. However, in high-end equipment such an approach leads to problems when designing circuitry that will not compromise the audio quality. The new method employed in the D-70 to maximize audio quality is to use a DAC locked to a direct crystal-controlled fixed-frequency clock. This allows the conversion to be carried out independently from the input frequency and input jitter is therefore eliminated. In the case of non-synchronization, the RAM Link buffer mentioned above eliminates any potential problems.
32kHz - 192kHz wide-ranging input sampling frequency, with 24-bit input
The D-70 is an advanced D/A converter compatible with all twochannel linear digital sources, as well as top-quality CDs. It conforms to the AES 3 standard for dual-wire (XLR) input when accepting data at 176.4 kHz or 192 kHz.
UP conversion feature allowing a maximum of 24 bit/768kHz
Two different filter algorithms: FIR (equivalent to HDCD), and RDOT can be selected at the digital stage. Custom settings can also be made, by using the two different filters in series, for up to 16 times oversampling. Firstly, employing the sharp roll-off characteristics of FIR, the more natural extended characteristics of RDOT doubling the frequency can then be added to produce a more musical result.
WORD SYNC output allowing synchronization with CD transports, DD converters, etc.
The D-70 is further enhanced by the inclusion of word sync outputs. This provides a very stable input to the RAM Link buffer, and helps enhance the natural nature of the final audio signal.
Three kinds of GIC analog filters on the left and right channels
Three different types of analog filter are provided in order to cope with the range of input sampling frequencies, from 32 kHz up to 192 kHz, and the most appropriate filter is automatically selected. These filters are based on secondary Butterworth GIC filter. The automatic switching system isolates all filters, except the active one, using relays, and inactive filters do not appear in the signal path. This combination of features has the effect of producing lossless high-quality filtered sound.
Discrete transformers for digital and analog circuitry
This system completely removes any intra-system interference, and provides clean regulated power independently for the digital and analog sides. This is the cleanest, most precise power supply that we can devise.
Ready for a IEEE 1394 interface (SACD and DVD-A format compatible)
IEEE 1394, the next-generation high-speed digital link, is in the process of inter-manufacturer standardization for employment with the SACD and DVD-A formats. As soon as the necessary steps for standardization have been agreed, the D-70 is ready - with the ability to add a IEEE 1394 interface to the rear panel. Rather than rush forward, we have decided to wait until the standards have been set for both SACD and DVD-A, allowing a dual simultaneous expansion of capabilities.
Super-solid body brings out the sound quality
A solid heavy (25 kg, or 55 lbs) body and chassis, uncommon on DAC units, enhances bass response and feeling, as well as improving the overall sonic performance. An 8 mm-thick steel base sheet totally isolates the unit from external vibration. Triangular pinpoint feet composed of hardened steel help to complete the mechanical isolation. Sturdy internal construction, using seven major functional blocks, electrically isolated and independent from each other to provide the best possible quality: digital, analog, power supply (digital), power supply (analog), AC primary, word clock and transformers.
While ordinary CDs are digitized to 16-bit resolution, discs mastered to the HDCD® (High Definition Compatible Digital®) standard use 20-bit resolution. Such discs are compatible with ordinary CD players, but in order to obtain the maximum benefit from the new process, you need an HDCD decoder. The D-70 is equipped with HDCD, and can decode HDCD recordings! HDCD system manufactured under license from Microsoft Corporation. This product is covered by one or more of the following:5,479,168, 5,638,074, 5,640,161, 5,808,574, 5,838,274, 5,854,600, 5,864,311, 5,872,531. Other patents pending., HDCD®, High Definition Compatible Digital®, and Microsoft® are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries.
Multiple features for the best possible sound
Multiple digital inputs (three types, seven sets) with XLR, RCA and TOS jacks Two types and two sets (XLR and RCA) of analog output, as well as a TOS optical digital output Integral digital volume control. With the volume control, it is possible to connect the D-70 directly to a power amplifier, eliminating the pre-amplifier stage of an audio system. The sound can be attenuated in 0.1dB steps to a maximum of -60dB (and infinite cut). Isolated pure D/A conversion - when the digital data has been read from RAM, the signal lines and the ground of the analog circuitry are electrically isolated from the digital side, resulting in pure D/A conversion. The DAC is composed of four multi-bit DAC Burr-Brown PCM1704 units, with an outstanding signal-to-noise ratio and exceptionally low distortion characteristics.
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