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Testing Ground

Solen MuDac-300: A Qobuzism for this DAC, designed and manufactured in France, for profound sound!

By Barry Moore |

First entry in the area of digital music from French brand Solen, the MuDac-300 remains prudent in its decoding capabilities (24-bit up to 192 kHz in any case), and opts for uncommon technical solutions leading to sonic results of the highest level. This one was an easy Qobuzism!

Solen is a French company located in the region of Grenoble and whose main activity from 1988-1998 was audio. Since then, they have moved towards the development of RF systems.

Solen did, however, revive it's activity in audio just two years ago with the CV40 and CV35 amplifier models, two high quality devices made entirely by hand in the traditional way. As well as that, the brand is completing the industrialization of the CT50N, the penultimate model of the range which incorporates both DAC and amplifier on one chip: Entirely symmetrical amplification technology.

The MuDac-300 will be the subject of this benchmark. Solen has decided to integrate the DAC with its catalogue following the warm welcome it received from discerning listeners. Note that the 300-MUDAC we lent Solen is a pre-series device welded by hand, but from now on manufacturing is expected to be contracted for assembly in Grenoble with an aim to expanding distribution.



Appearance

A very sober presentation for the Solen MuDac-300, whose aluminum body is adorned with a smoked Plexiglas façade, maintained at its ends by two small, slightly protruding aluminium parts.


The on/off function is engaged by gently pressing the area on the left of the front panel (illuminated permanently ON/OFF). Under pressure, the central part of the façade reveals the logo and brand name with backlight, and the source selector (to the right) which uses the same principle as the on/off button. Five red LEDs located under the central logo indicate the input (S/PDIF or USB) and the sampling frequency, whether 44kHz or 48kHz, 88kHz or 96kHz and 176kHz or 192kHz.


The connectivity includes the coaxial jack for the AC adapter, a USB input for connecting to a computer, smartphone or Android tablet, S/PDIF coaxial and stereo audio outputs, unbalanced on Cinch taken or balanced on XLR, a switch to choose between them and exclude any simultaneous operation.


Manufacturing

The electronic makeup of the MuDac-300 consists of a main circuit which is contained on the rear face of the device, while a second circuit responsable for control and signaling is mounted perpendicularly, therefore reaching the front face of the device.

The central part is not a display, but rather a backlight which shows the logo and brand name when light is diffused through the Plexiglas design of the front panel. The same method is used for the on/off functionality and source selection.


The device we had on loan is a pre-production model, so the primary circuit includes a few changes and the USB interface is a separate card, knowing that, on commercialised products, the USB processor will be integrated directly into the main circuit (in the area devoid of components located on the top left of the visual below).


The power supply of the MuDac-300 is of the linear type. Voltage from the mains transformer is first rectified and then filtered by two 2200μF / 25V electrochemical capacitors to produce two symmetrical voltages which are then stabilized at + or - 11V, adjustable by the LM317 and LM337 regulators (mounted on the radiator) in order to power the analogue portion. There are also two other controllers for digital circuits, LM317 and LM317L, containing four 1000 uF / 16V electrochemical capacitors, and two 1000 uF / 25V.


The USB interface is a generic model sold by Audiophonics and is equipped with a multi-core XMOS 8L6C5 preceded by USB interface SMSC (Microchip), USB3318.

Contrary to what is generally done, Solen opts not to use the USB bus I2S signals extracted by the XMOS processor, but rather the S/PDIF signal recreated by the same processor through the I2S bus. The S/PDIF signal comes from the coaxial digital input through an 8-input S/PDIF Wolfson WM8805.

This approach surprised us, due mainly to the fact that, as a result, we are witnessing two conversions (USB to S/PDIF, and S/PDIF to I2S) but Solen explained that it takes advantage of an excellent PLL (Phased Locked Loop) integrated with the WM8805 for digital signals from the USB as well as for signals arriving via the optical input. The WM8805 delivers a high quality sound, offering a reduced jitter of 50 ps (a pass through option also allows this chip to simply transit through the digital audio signals with the aim of improving restitution).


The digital to analogue conversion is assigned to two Analog Devices AD1955A chips (24-bit at 192kHz, a chip for each channel), leaving the differential signal in the form of a current. This is where Solen have set themselves apart - by not using operational amplifiers for converting these currents into voltages, but rather performing this operation in a completely passive manner using resistors coupled with audio processors.


On the other hand, the limited bandwidth regarding the reproduction high-pitched tones of these transformers eliminates conversion residues without using a low pass filter, usually made around operational amplifiers. We find, consequently, no activity at this level, even against feedback, which can only be conducive to the sound reproduction.


The signals are then amplified by the output levels, each of which includes a voltage amplification transistor and two transistors (BD139) in push-pull class A for supplying power to the preamplifier connected to MUDAC-300, in both asymmetric and symmetrical mode. These transistors are mounted on the same radiator as the two regulators providing power.

No blocking capacitor is used on the path of the output signal in order to maintain its purity, the DC voltage output is maintained at 0V through a circuit built partly around a TL072 operational amplifier.

Here's what the manufacturer says about this part of the electronic makeup "The transformer/triplet association of the transistors is part of our philosophy: To strive for a minimalist structure, optimized in its settings, with a minimum of feedback and maximum transparency."

Listening

As for sound performance, the very high level of technical solutions adopted by Solen for the MUDAC-300 makes it undoubtedly one of the best we have listened to here at Qobuz.

When listening to extracts from Mozart's Le nozze di Figaro by Pier Giorgio Morandi conducting the Hungarian State Opera Orchestra we are once again struck by the purity of the restitution, which allows the female voices to express themselves with clarity, lending a global transparence to the sound and a truly impressive authenticity. This is something we note regularly with devices that avoid using feedback wherever possible. In short: incredible.

Another musical genre now, but emotions equally guaranteed with My Sweet Lord from the album All Things Must Pass by George Harrison where the chords are rich and sharp without any acidity. The singer benefits from an impressive presence, with the choral and instrumental accompaniment remaining light in a vast sound space.

The song The Sun Is Gonna Rise Again from the album Where I Belong by Cris Cab benefits from a brilliant restitution, with firm and powerful bass. There is no harshness in the sound, with every musical note remaining well-defined throughout, even at sustained high volumes.

In conclusion, we are very pleased to present this Qobuzism award to the Solen MUDAC-300, a French offering with sound performances of the highest level and one which implements innovative solutions, chosen not because they meet the latest technological trends, but rather because they let the music speak freely.


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