Audio Note DAC 0.1x Valve Digital-to-Analogue Converter

The Audio Note DAC 0.1x converts compatible digital audio from a CD transport, streamer or computer into an analogue signal for a conventional amplifier or preamplifier.

It uses a Philips TDA1543 stereo digital-to-analogue converter and a zero-feedback analogue output stage built around a 6111WA valve.

One 75O RCA coaxial S/PDIF input and one USB input provide connections for two different digital sources.

What Does a DAC Do?

Digital source components store or transmit music as numerical data. An amplifier requires an analogue electrical signal, so a digital-to-analogue converter must translate the digital information before it reaches the amplifier.

The DAC 0.1x receives compatible digital audio through its coaxial S/PDIF or USB input, performs the conversion and sends a fixed-level stereo analogue signal to the connected amplifier or preamplifier.

Volume remains under the control of the downstream preamplifier or integrated amplifier.

Audio Note 1x Oversampling Design

Audio Note describes its digital conversion system as 1x oversampling Direct From Disc technology.

In practical terms, 1x means that the incoming sample rate is not multiplied by a conventional oversampling filter before conversion. This is often described more generally as a non-oversampling or NOS architecture.

Audio Note's design does not use the conventional oversampling, noise-shaping, jitter-reduction or re-clocking processes found in many digital products.

This is a deliberate circuit-design choice rather than a selectable listening mode. The DAC cannot be switched between oversampling and non-oversampling operation.

No Conventional Digital Filtering

Many DACs apply digital filtering and additional signal processing before the audio reaches the converter chip.

Audio Note takes a different approach by presenting the reformatted digital signal directly to the converter without conventional oversampling filters.

The company also avoids the usual corrective processes associated with noise shaping, jitter reduction and re-clocking. This simplified approach is used throughout the Audio Note DAC range.

Philips TDA1543 Converter

Digital-to-analogue conversion is performed by a Philips TDA1543 stereo converter chip.

The TDA1543 is a 16-bit converter and forms an important part of the DAC 0.1x's deliberately straightforward digital architecture.

Audio Note specifies input sample-rate capability at 44.1kHz, 48kHz and 96kHz. The connected source must therefore be configured to provide a compatible signal.

Designed for Compatible PCM Audio

The published specification identifies conventional digital sample rates rather than support for every modern digital-audio format.

The source should provide a compatible PCM signal at 44.1kHz, 48kHz or 96kHz. Native DSD, multichannel audio and other unsupported formats may need to be converted by the source before they reach the DAC.

Output settings should be checked when connecting a television, streamer, computer or other multipurpose source. Selecting stereo PCM is normally the appropriate starting point.

75O Coaxial S/PDIF Input

The coaxial digital input uses a single RCA socket with a specified 75O impedance.

It can be connected to a compatible CD transport, network streamer or another source equipped with a coaxial S/PDIF output.

A purpose-designed 75O digital coaxial cable should be used rather than a conventional analogue interconnect.

A CD transport such as the Audio Note CDT Three can provide a dedicated disc-playing source for the DAC.

USB Digital Input

The USB input allows a compatible computer or digital source to send audio directly to the DAC.

The playback application and operating system should be configured to use the Audio Note DAC as the audio output device and to supply a supported sample rate.

USB host compatibility, adapter requirements and available output formats can vary between computers, tablets, phones and streamers. Compatibility with the intended source should therefore be confirmed before ordering.

No Optical Digital Input

The DAC 0.1x does not provide a Toslink optical input.

A television, streamer or disc transport equipped only with optical output cannot be connected directly. A suitable external digital interface would be required, although a source with native coaxial S/PDIF output will usually provide the simpler solution.

6111WA Valve Output Stage

After digital-to-analogue conversion, the signal passes through an analogue output stage using one 6111WA valve.

The valve stage operates without negative feedback and provides the fixed line-level signal sent to the connected amplifier or preamplifier.

The 6111WA is an internal valve rather than an exposed valve fitted on top of the chassis. Replacement and internal servicing should only be carried out by a suitably qualified technician.

Zero-Feedback Analogue Stage

Audio Note does not apply negative feedback around the DAC 0.1x analogue output stage.

The design instead relies on a simple valve circuit and careful matching with the connected amplifier or preamplifier.

This approach is consistent with the wider Audio Note design philosophy used across many of the company's source components and amplifiers.

Fixed 2.6V Line-Level Output

The DAC 0.1x has a reference output level of 2.6V RMS.

This is a fixed output rather than a variable preamplifier output. The DAC should therefore be connected to a line-level input controlled by an amplifier or preamplifier with its own volume control.

The published output level is slightly higher than the 2V commonly associated with many CD players. A change in listening volume may therefore be noticeable when comparing the DAC with another source using the same amplifier setting.

Output Impedance and Amplifier Matching

Audio Note specifies an output impedance of less than 2kO.

The connected line input should present a suitable load, and analogue interconnects should be kept to sensible lengths.

Most conventional integrated-amplifier and preamplifier line inputs will provide an appropriate starting point, but compatibility should be confirmed when partnering the DAC with unusually low-impedance equipment.

Compact Chassis

The DAC measures 96mm high, 300mm wide and 270mm deep, including its connectors.

At 3kg it is considerably more compact than many full-width source components, but it still requires a stable shelf and sufficient room for its mains, digital and analogue cables.

Avoid placing it directly on top of a power amplifier or another component that produces substantial heat.

Warm-Up and Ventilation

The internal valve and power-supply components produce heat during normal operation.

Allow air to circulate around the chassis and avoid installation inside a tightly enclosed cabinet.

The DAC may require a short period after switch-on before its operating conditions stabilise. There is no need to leave it powered continuously when it is not being used.

Black or Silver Finish

The Audio T product options currently list black and silver versions.

The silver version uses an anodised aluminium fascia, while the black version uses a black acrylic fascia. The internal digital and valve circuitry remains the same, so the choice is primarily visual.

Audio Note also publishes a white acrylic fascia as a possible manufacturer finish, but this is not currently shown as a selectable option on the Audio T product page. Please contact your Audio T store if a finish is not listed.

Key Features

• Dedicated stereo digital-to-analogue converter
• Audio Note 1x oversampling Direct From Disc circuit topology
• No conventional digital oversampling
• No noise shaping
• No jitter-reduction processing
• No signal re-clocking
• Philips TDA1543 16-bit stereo converter
• 44.1kHz, 48kHz and 96kHz input capability
• One 75O RCA coaxial S/PDIF input
• One USB digital input
• 6111WA valve analogue output stage
• Zero negative feedback in the output stage
• 2.6V RMS fixed reference output
• Output impedance below 2kO
• Specified channel balance below 0.25dB
• Compact 300mm-wide chassis
• Black acrylic or anodised aluminium fascia

Frequently Asked Questions