“Approach to Blu-ray Pure Audio”, High Fidelity, Polonia, August 2018
Following his interview of Blu-ray discs producer Mr. Mark Waldrep of AIX Records (Los Angeles, USA), chief editor of High-Fidelity…
Seguir leyendo >JMF Audio DXC 2.2 MkII
Technical characteristics
| Clock recovery mechanism | MCLK3 proprietary vari-speed 3-stage-locking mechanism with reference to the local master clocks |
| Clocking system | master DAC concept with 2 made-to-measure ultra low jitter master clocks in MCDC proprietary clock circuits |
| Supported resolutions | 16..24bits/ 32, 44.1, 48, 88.2, 96, 176.4, 192 kHz |
| DAC section | |
| Digital to analog conversion technology | DA768 w/ DMSS topology on proprietary PGP multilayer gold plated substrate |
| True digital to analog conversion rate | 705.6 kHz or 768.0 kHz depending on input |
| Total harmonic distortion plus noise at full output | 0.0008 % at 1kHz typical** (bw. 22Hz .. 22kHz) |
| True audio dynamics (EIAJ measurement) | 130 dB typical** (real! no auto-mute function!) |
| True signal to noise ratio (full output, XLR) | 130 dBA typical at 1kHz** (real! no auto-mute!) |
| Output level range control | passive attenuators, remotely controlled |
Description
Converting bit streams to real signals… Caring for the music…
JMF Audio presents the 768kHz DAC, 4x the limit of Blu-ray and 8x the equivalent of SACD.
To the JMF Audio’s 30 year expertise in analog audio electronics, recognized from American studios to Japanese music lovers, skills in psychoacoustics and an unique approach to digital circuits for the music were added through the founder’s sons.
The first researches of JMF Audio in digital audio and signal conversion were conducted to meet internal needs, by passion and challenges. It was also about assessing the potential for improvement in a field commonly considered as close to perfection. The results quickly showed that by addressing points which importance has often been underestimated, the solutions that JMF Audio could develop favored the expression of the musical work.
The digitization of the audio signal offers many advantages for transfer and storage. To enjoy listening, however, it is necessary to convert the digital codes into continuous signals evolving over time. JMF Audio is approaching so-called digital signal processing and the crucial step of its conversion, in an innovative way, in a globally analog way…
A converter (DAC) translates a quantized value into an analog magnitude at a time T. The music information will be extracted by successive high frequency conversions. The relative temporal stability between conversions is a key parameter. The time information can be provided by the disc drive or by the file server. It is based on clocks. But these clocks are analog components by nature, with their characteristics of phase jitter and spectral density power (variability of periodicity).
The highest temporal accuracy is therefore necessary to ensure a conversion that is faithful to the original. However, guaranteeing it with musicality is a challenge. For the DXC 2.2 MKII converter, JMF Audio has developed the concept of synchronization and local timing named MLCK3 based on its own clock circuits placed near the conversion stages, to ensure maximum signal integrity.
With the advent of the CD, the sampling frequency of the audio signal was defined at 44.1 kHz, which according to Shannon’s theorem is sufficient to quantify the highest frequency signals audible to the human ear. Recording studios worked on higher frequencies such as 48kHz. DVD and Blu-ray formats allowed sampling frequencies up to 192 kHz. Increasing the sampling frequency at the recording would make it possible to quantify ultra-sonic harmonics of the musical instruments… The often-ignored aspect is that this actually reduces the constraints on the spectral image rejection during the sampling, which makes the process more transparent by improving its impulse response…
Based on our psycho-acoustic studies on this phenomenon, JMF Audio has developed a conversion technology operating at 705 or 768kHz, which means 16 times better than the CD format, and still twice as high as the internal DXD format of some mastering machines. This is in order to ensure a faithful representation of the digitized information and to obtain a directly analog signal, because very fine, without the need for post filtering. A world first in 2003… An achievement with the DXC 2.2 MKII, named DA768.
These innovative technologies have led to a rendering of atmospheres, nuances, soundstages, and a fluidity of interpretations that is second to none.
> DXC 2.2 MKII is ultra high performance, universal, future proof yet clean and simple to use.
> MCLK3 locking mechanism is JMF Audio’s smart answer to clocking issues with transports.
> USB module permits bit-perfect operation with isolation and local synchronization.
> DA768 conversion rates of 705.6 and 768kHz allows PCM audio to outperform DSD (SACD).
> DMSS super symmetrical conversion on gold plated substrate, an analog piece of art.
|
 |
> Via a standardized link, MCLK3 extracts an incredibly detailed and natural sound.
The main digital audio board handles the standardized audio S/PDIF and professional AES-EBU inputs and embeds the reference master clocks. The USB module comes as an add-on. Because JMF Audio believes that digital electronics in a DAC is a matter of analog design (clocks are analog components by nature), a special attention was paid on the development of this new main digital audio board incorporating many innovative features. The two S/PDIF and two AES-EBU audio inputs are independent and galvanically isolated. The clock and data recovery from the audio source is performed by the newly designed proprietary MCLK3 vari-speed 3-stage-locking mechanism that takes reference from the local master clocks through the MCDC master clock distribution circuits.
The MCDC circuits feature two shielded bespoke master clocks. One is used as reference for input sampling rates multiple of 44.1kHz and the other is used for sampling rates multiple of 48 kHz.
From the implementation of these concepts has resulted a digital electronic circuit board which serves the music.
> Unrivaled precision timing. High resolution is nothing without precise time reference.
The MCLK3 principle contributes to the fluidity, to the natural rendering, to the true dynamics and “analog” feel that surprises the listener. The optimum is assured with a single S/PDIF or AES-EBU connection, simply, up to 176.4 and 192kHz sampling rates.
The JMF Audio DMT 3.7 transport plays SACD and Blu-ray Pure Audio discs (192kHz), PCM and DSD files and connects to the DXC 2.2-MKII using an AES-EBU interface.
> The DXC 2.2 MKII’s USB module offers the highest quality way to take advantage of files from your computer.
The USB module allows the connection of an audio server, typically a personal computer on which an audio software player has been installed. As explained in the previous paragraph, the USB module is an add-on to the main digital audio board. The USB module is extractible from the chassis, which makes the DXC 2.2 MKII open to upgrades to follow possible future computer audio interface standards.
The USB module features a galvanic isolation, preventing the DXC 2.2 MKII from being subject to the electromagnetic interferences from the computer environment. This module is enclosed in an aluminum shield case and takes advantage of a dedicated power supply.
As opposed to the S/PDIF and AES-EBU interfaces that carry audio information continuously, data over the USB interface are transferred in packets. The USB module hence operates asynchronously with the computer, via a bi-directional communication. The samples are requested from the computer which provides them to the main digital audio board at the pace imposed by the DAC’s local master clocks.
> DA768‘s conversion rates of 705.6 and 768kHz allows PCM audio to outperform DSD (SACD).
The conversion section named DA768, another masterpiece and jewel inside the DXC 2.2 MKII, converts bitstreams into physical magnitude. The DMSS conversion architecture followed by an ultra high precision analog section ensures unparalleled conversion linearity. The very low level information that represents the subtle nuances in the artists’ play and the most subtle ambiances are extracted and correlated to the musical content. This results in an extraordinary homogeneous rendering.
The DA768 board features discrete ultra-low noise level surface-mounted components and custom-made capacitors. All the components and connectors of the audio path have been selected based on technical and reliability criteria, as well as on listening for their natural sound characteristics.
The JMF Audio proprietary PGP pure gold finish of the multi layer printed circuit board is incompatible with the automated processes. The hundreds of components populating both sides of the board are hand mounted and soldered one by one by our specialized technicians with JMF Audio’s bespoke solder, using a magnifying glass. A work of art that recalls jewels manufacturing.
> DMSS super symmetrical conversion on gold plated substrate, analog piece of art.
Featuring a deactivatable volume control, the DXC 2.2 MKII can directly control a power amplifier. In fact, the output stages inherit technologies employed in the PRS 1.5 preamplifier. In the pure analog section, the new DA768 board embeds a passive attenuator controlled by the HIGH / LOW switch located on the rear panel. The output level range can be adjusted according to the sensitivity of the driven device. When the DXC 2.2 MKII is used with variable volume, enabling the output attenuation optimizes the conversion resolution and the dynamic range.
> The DXC 2.2 MKII was designed to be a timeless jewel.
After selection on technical aspects, refined selection on measurement, the final decision on absolutely all the audio components that the DXC 2.2 MKII contains has been taken after long listening tests in the JMF Audio’s studio. From the remake (MKII) of the DAC series up to its current revision (see bottom of page), JMF Audio’s investment in research and development has been continuous.
The JMF Audio elements are entirely hand crafted in our workshops and pass severe tests. Since revision B, every DXC 2.2 MKII has even been verified by listening in our studios after an operational period of over 100 hours, so as to ensure its future owner will receive the best.
About MQA by Bob Stuart:
We are pleased to announce that the JMF Audio digital to analog converters are compatible with the MQA’s most important aspect by nature. Indeed, JMF Audio has designed DACs converting as high as 768kHz for all input rates in order to present a sharp “analog like” impulse response, since 2003…
When playing an MQA-CD or file, including an estimated compensation of the blurring effect on the recording side, the result would be unhindered by the DXC2.2 MKII.
MQA also includes a data size reduction feature for easier download and storage, which is mostly interesting for portable audio devices and streaming. When playing MQA files, unfolding should be done with the computer/server.
Related News & Reviews
