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Vi DAC unit - more detailed information

The World's Most Versatile DAC

Vi DAC's versatility is unmatched. It features five digital inputs: one USB, one TOSLINK, one AES/EBU, and two S/PDIF. It outputs your analog music in two different ways. First, it has two headphone outputs on the front panel. One 1/4" single-ended output, and one four pin XLR balanced output. Second, it outputs at line level through one pair of RCA single ended outs and one pair of XLR balanced outs. If you choose Vi DAC Tube, you'll get another pair of single-ended RCA outputs through the tube buffer stage. Additionally, if you choose the balanced tube output option, you'll get another pair of balanced XLR outputs.

Advanced 64 Bit Volume Control

In the past, attempts to engineer digital volume attenuation has been panned by audiophiles due to its very obvious "digital-ness." Analog volume control has been preferred, though it also presents a problem because of the noise that it generates. We've taken a different approach to volume control with our advanced 64 bit attenuation circuit, which uses an ultra-high resolution, zero noise, bit perfect mechanism.

In the case of computer-based playback via USB, Vi DAC's volume attenuation circuit replaces the computer's volume calculations with its own, ensuring that your music remains bit perfect all the way through the conversion process. This way, it ensures that no information is lost before Vi DAC gets the data.

Automatical Digital Volume Control Shut Off

If you want to use the analog volume control of your preamplifier,set Vi DAC's digital volume attenuation circuit to -0dB, which completely bypasses the digital volume control circuit.

Individual Channel Control

In order to keep the digital music bit perfect, we've designed Vi DAC so that once it's volume is set to -0db, you can control the individual channels' attenuation settings to adjust balance.

User-Selectable Digital Modes

Most DAC aficionados understand the importance of digital filters. One of the major functions of digital filters is to remove the digital artifacts that the digital-to-analog conversion process adds to the signal.

Vi DAC features several user-selectable digital modes that go beyond digital filtration. These modes were developed specifically to Vi DAC (all of our products feature digital modes specific for their application even though they may share the same name product to product). These modes not only change digital filtration settings, but also the digital PLL windows of the internal DAC IC, the re-clock jitter removal circuit, along with other hardware installed into the DAC.

Users get the benefit of continuous upgrades to their digital modes through firmware releases.

TCM (Time Coherence Mode) uses LH Labs' minimum phase digital filter and time optimization algorithm, which removes all PRE-ring from the converted signal and realigns the impulse response. This presents the listener with a more well-defined and natural soundstage. In short, this mode is optimized for time domain response.

FRM (Frequency Response Mode) uses a slow roll-off linear digital filter and frequency domain optimization algorithm to provide a smoother and clearer sound with even lower THD+N in the high frequencies. The IMD in the higher frequencies is lower because of frequency response and high frequency artifact optimization.

FTM (Femto Time Mode) minimizes the bandwidth of the DAC IC's digital PLL, providing even better jitter performance and better sound quality. Available for ALL of our femto clock equipped DACs.

SSM (Stable Streaming Mode) is designed to optimize Vi DAC for streaming music. This mode combats two most important issues of streaming your music: time-fluctuated high jitter music content, and compressed roll off of high frequency harmonics. With SSM, Vi DAC will restore your streaming music's timing using our patent-pending three layer buffer. Expect a richer sound in the mid and high band frequency range.

Choose Your Music Format

Vi DAC decodes PCM (the most common music format, the one used in your CD's and MP3's) with bit rates of 16, 24, and 32 bits, and sample rates of 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz, 352.8 kHz, 384 kHz. It also natively decodes DSD music files (a rapidly-growing digital download format that audiophiles tend to love), letting you choose between five different filter modes, with sample rates of 2.822 MHz, 3.072 MHz, 5.644 MHz, 6.144 MHz, 11.288 MHz, and 12.288 MHz.

Dual Femtosecond Clocks

When it comes to digital audio playback, timing is paramount. The more accurate the timing, the more true to the original recording the playback is. For the most accurate timing available, we turn to femto clocks.

Femto clocks are so named because they are accurate to a femtosecond. That's one millionth of one billionth of a second! Clocks like these aren't typically found in audio devices. They're usually in missile guidance systems. If you can find a DAC with a femto clock in it, you're on the right track. But the application of the clock (in our case more than one) is super important. For example, if you choose a clock that's accurate to a femtosecond but the frequency at which is oscillates is not a whole number integer of the audio frequency you're decoding, you still end up with jitter, the sworn enemy of high-performance digital audio.

Our ultra-low jitter femto clocks are customized for us by Crystek Crystals, and are accurate to 85 femtoseconds when properly warmed up. Each DAC that uses them requires two separate clocks. One clock oscillates at 90.3168 MHz for audio signals that are sampled at a rate that is an integer multiple of 44.1 kHz, and the other oscillates at 98.304 MHz for audio signals that are sampled at a rate that is an integer multiple of 48 kHz.

Our proper implementation of dual femto clocks ensures that the lease amount of jitter is introduced into the digital audio signal prior to its conversion into analog. The highest degree of harmonic integrity is retained, making the converted analog signal true to its digital origen. This translates to deep, black background, which gives the listener a sense of space and imaging that is unmatched in any DAC at any price.

Non Parallel Walls

Vi DAC's chassis has been designed to dissipate vibrations within the chassis that could otherwise be converted into electrical noise. By making a design without parallel walls, standing waves don't build up in corners, making it much less likely that noise will get into the circuit. This innovative design, based on our Da Vinci DAC's original chassis specification also creates enough internal volume to accommodate larger components such as capacitors and tubes.

Descended from Da Vinci DAC

Ultra-quiet Linear Power Supply

Vi DAC's linear power supply employs 26 high quality regulators, including 4 discrete shunt regulators, making it among the quietest linear power in the industry. In addition, the power circuit is completely isolated from the digital and analog circuits, preventing mechanical noise from the transformer from entering the signal path.

Proprietary Three Layer Elastic Buffer

To ensure computer speed fluctuations don't smear your music, we've developed a proprietary (and patent-pending) Three-Layer Buffer similar to the buffering technology many of today's high-speed computers employ. This is the first time such a design has been applied to audio.

Bipolar Instant Power Technology

To address the issue of energy during power hungry times, our output stage uses an extremely low output Z bi-polar power supply, which keeps at least twice the rated power in reserve just in case you want the cannons in Tchaikovsky's 1812 Overture to feel like they're taking aim right at you.

DSD Direct Mode

Mathematically speaking, there's no such thing as a lossless method to convert PCM to DSD, or vice versa. Additionally, there's no single conversion engine in the world that's optimized for both formats. That's why Da Vinci Dual DAC has two separate conversion engines: R2R for PCM conversion, and delta-sigma for DSD.

Vi DAC uses a single conversion engine from ESS. In PCM mode, ESS delta sigma engine has FIR filter and digital volume control in the front. While in DSD decoding, and you turn on the "DSD Direct Mode" from Vi DAC's menu. DSD Direct Mode bypasses these two mechanism, give your DSD music intact and shortest internal path.

Optional Dual 2015 ESS SABRE9018AQ2M DAC Chips

Vi's DAC's design has always been to utilize ESS' Sabre 9018 DAC microchip for its digital to analog conversion. New for 2015, ESS has released the 9018AQ2M, which boasts even better harmonic distortion characteristics than its predecessor, as well as a lower noise floor and greater dynamic range. You have the option to utilize this new chip if you so choose.

For more info on ESS' new SABRE9018AQ2M, please click here.

Optional Hybrid solid-state/tube output buffer

A DAC has two main parts. First, the digital stage, and then the analog stage. Vi DAC's digital stage utilizes an advanced, proprietary solid-state design first implemented in our Da Vinci DAC. In the digital stage, precision timing and decoding is the most challenging part. Without precision, details blur and smear. The analog stage is where the magic happens. Vi DAC's solid-state analog stage is both musical and controlled at the same time. We've also designed an optional tube output buffer for those afficionados that love the warm and liquid sound of tubes.

Put Analog Back Into Your Music

For so many of us, the drawback to listening to digital music is that is sounds too, well, digital. Vi DAC does a great job delivering both precision and warmth to your stereo, but if you really want to put analog back into your music, choosing the optional Tube output buffer is a must. It uses 6922/6DJ8 tubes to give you a very wide bandwidth, and a low noise floor. With its warm and charming characteristics, prepare to spend a lot more time listening to your music!

Vi DAC's Tube Buffer Nerdy Highlights
Active Biased Parafeed Single-ended (ABPS) Tube BufferUltra-wide bandwidth design (100k Hz in this stage)Bessel Analog Filter before tube gridUltra-low noise discrete shunt regulator for B+Dedicated heater transformer and B+ transformer (only seen in very exotic designs)Soft start power network to make your tubes last longer.Zero global negative feedback8 zero switching noise Schottky diodes4 Elna Silmic II capacitors for power decouplingNichicon MUSE-BP capacitors for active bias circuit decouplingNichicon DB-GB series bipolar high-end capacitors for critical tube power couplingKOA non-inductive resistors in gridWIMA FILM CAPS to remove the final minor trace of power noise in B+Non-magnetic metal film resistors throughout.

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