Test of ALEF (Delta Sigma) Duet SE power amp

"Wonderful exercise of style this amplifier Alef Duet SE. Starting from a proprietary circuitry that can be tuned, if necessary to the need and wishes of each owner, the manufacturer propose a device capable to satisfy all situations.., This is the conclusion of the test done by "Haute Fidélité" resulting in their most presigeous award "Reference"

Here the preliminary translation of the article appeared on French magazine Haute Fidélité:

ALEF DUET SE, an electronic made “sur mesure” (ad hoc, on custom desire).

This stereophonic block is the work of Domenico Simonetti, passionate Italian, and creator of  Delta Sigma.  

Designed to accommodate the wishes and the needs of each customer, this electronic is full of technical subtleties which some are still kept secret...

The Delta Sigma adventure began about ten years ago thanks to the dynamism of its creator, a journalist specialized in audio and emerging technologies. The quality and the originality of the projects as well as the musicality of the circuits gave to the manufacturer the access to many installations without compromise. Delta Sigma is then interested in high end market and is able to offer equipment which performances are extraordinary stunning. The North Pole preamplifier powered on batteries illustrates the savoir faire of the manufacturer. J - FET transistors working in pure class A with bandwidth of 3MHz. For reasons of homonymy, Delta Sigma was recently renamed Alef. The name has certainly changed but the originality and exclusivity of the circuits have always M. Simonetti’s signature.

Haute couture of electronics

While the most prestigious manufacturers design offices increase their imagination to innovate in terms of presentation and finish of their creations, Alef takes everything the other way around and revisit the look starting from a primary volume of solid aluminum and small fine aesthetic touches here and there. This is pure genius of Italian design. The chassis is an assembly of anodized solid aluminum parts very finely brushed. These parts are nested and screwed together to leave no visible screws on the front and on the top of the device. The front consists of two very thick plates (25mm) with engraved logo of the manufacturer and model name. They are separated around a vertical luminous banner based on blue LEDs. They lights on when we activate the power switch installed at the base behind the front edge. Two large solid aluminum heatsinks serve as side walls. The top cover is finely finished. The back panel is kept in place by Torx fasteners in stainless steel, it receives RCA and XLR connectors, two pairs of speakers binding posts in solid copper and the power inlet is a Neutrik Powercon connector. This professional connector provides an exceptional mechanical stability, very much superior to common IEC connector, and a very high quality of electrical contacts. Finally, be aware that Alef can tailor each client desires finishing and each device connectivity. A gold plated Alef Duet SE with connectivity Goertz pure silver? Yes, it is possible!

Professor Simonetti Alchemy...

If a chassis production industrialization seems well possible even if complex, it is downright impossible for electronics manufactured and hand assembled by artisan expertise. The power cable provided with the device cable is fully handmade with different diameter conductor wires and shielded. The Duet power is supplied from two transformers capable of 680 VA each. They are lying on thick quartz powder then drowned in the resin in a very expensive mu-metal shielding enclosure and all suspended by several silent blocks. So, magnetic radiation and mechanical vibration transmissions are completely suppressed. All internal cabling is made by Litz ultrapure copper. The audio schema remains secret but based on an asymmetric single end configuration. The power stage operates around 10 transistors per channel in parallel with a minimum local feedback. Capable of issuing 180W under 8 ohms in class AB, including 15 in pure class A, they can provide approximately 600 W on as low as 0.1 ohm loads (one tenth of ohm), this proves the incredible stability of the circuit. Announced impulse power exceeds 10 000 W... It will be possible to adapt the Duet characteristics depending on the specifics of the installation where it will interface. Input sensitivity, the overall gain, class A functioning, bandwidth etc, may be preset by manufacturer according to the needs of the customer. All or almost all components are manufactured on custom specification. The ultra low noise precision resistors as Wima capacitors are asking for 15 weeks delivery time,  thse components that are likely to pick up electromagnetic interference hand shielded with a copper foil and grounded. Printed circuit board tracks are thick a quarter of a millimeter, at least four times more than what's best currently available. Finally, the very high power reserve is provided by many small fast capacitors wired in parallel and positioned as close as possible to active devices.

Listening: The Duet SE received for the test was configured “standard” to be used with a majority of speakers under typical conditions. Knowing that the manufacturer is able to draw much more, it is yet stated as one of the most accurate electronic we ever had between the ears. The variety of tonal colors contributes to an amazing realism of the reproduction, exacerbated by the use of the power cable Energia, which is essential. It provides so much information in terms of researched and harmonic details (atmospheres, aftermath of notes) that it would be a pity to remain just the basic cable supplied with the amplifier, at least two qualitative steps behind. Dynamic: The Alef deploys much energy on transient and we hear this. The magnitude of a contrabass line played at high level gives a real sense of presence in the room. The touch of chords are clear and clean, the sound is articulated, there is no volume exaggeration with the big resonant percussion meaning the Alef sovereign control in first octaves. On battery strokes as well as for balls impacts on a timbale, we feel precisely and distinctly the emitted sound impulse at any note attack followed by the skin vibrations.

The dynamics of this amplifier is evenly distributed on all the audio bandwith, no part of the spectrum seems disadvantaged. The track “Trittico” by Vaclav Nelhybel rich in brass and percussion is rendered with all the necessary spectacularity. The partition for brass is a voluntarily shiny interpretation analyzed by the Alef in an incisive and powerful way.

Soundstage: A lot of credibility in soundstage message from this Italian stereo block. It is true that, with such timbric qualities associated with a dynamic without compressions, narrowly could be expected a scrupulous analysis of the musical signal, favorable to a very realistic sound stage. It is therefore the case, proportions virtually draw in space create a tangible holographic illusion with a very net positioning of sound plans. Reproduction intelligibility is never taken in default, the Alef contributes to an alive, singing, melodic restitution.

Transparency: This electronic deliver a very pure listening, very neutral. I am almost tempted to say that they would be the others electronics to which it is associated with that will eventually color the result. The bandwidth, very broad on paper, it is also is subjectively. The very rigorous bass mixes strength and firmness, the medium reminds the one of a triode approaching the best of them, the high sings and fly without shortness or roughness. The overall sesult is very balanced and proves to be highly subtle, particularly when the Alef works in pure class A.

Virdict:

Wonderful exercise of style this amplifier Alef Duet SE. Starting from a proprietary circuitry that can be tuned, if necessary to the need and wishes of each owner, the manufacturer propose a device capable to satisfy all situations, offering a clear, precise  and defined reproduction from the extreme bass to the extreme high. The amplifier is able to play loud, very loud, without any audible sign of stress, or to distil a delicate melody at low volume, in class A. It can do almost everything, and does it well. The price is relatively high, but it benefits of a hand made manufacturing and of “sur mesure” concept, unique in the world.

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