Country of Origin
This review published in January 2026 on HifiKnights.com. By request of the manufacturer and permission of the author, it is hereby syndicated to reach a broader audience. – Ed.
Reviewer: Dawid Grzyb
Transport: Innuos Statement, fidata HFAS1-S10U
DAC: LampizatOr Horizon360 w. Stradi 5U4G + Psvane Art TIII 4x KT88 / 2x 6SN7
USB components: iFi audio Mercury3.0
Network: Fidelizer EtherStream, Linksys WRT160N
Preamplifier: Trilogy 915R, Thöress DFP
Amplifier: Trilogy 995R, FirstWatt F7, Enleum AMP-23R
Speakers: Boenicke Audio W11 SE+, sound|kaos Vox 3afw
Headphones: HifiMan Susvara
Interconnects: LessLoss Entropic Process C-MARC, Boenicke Audio IC3 CG
Speaker cables: Boenicke Audio S3, LessLoss C-MARC
Speaker signal conditioning: LessLoss Firewall for Loudspeakers, Boenicke ComDev
Anti-vibration conditioning: 12x Carbide Audio Carbide Base under DAC, preamp and speakers
Power delivery: Gigawatt PC-3 SE EVO+/LC-3 EVO, LessLoss C-MARC, LessLoss Entropic Process C-MARC, Boenicke Audio Power Gate, ISOL-8 Prometheus
Equipment rack: Franc Audio Accessories Wood Block Rack 1+3
Review component retail: $1'972/ea.
The strong silent type. The Firewall 640x Stellar is the Lithuanian LessLoss brand's most refined take yet on passive power conditioning, distilling years of noise-rejection development into a compact inline form. This firm have long approached audio design through the broader scope of noise. Rather than treating it as an unavoidable consequence of modern systems, the company consistently framed it as a variable that can be addressed deliberately. This position is clearly communicated by the current catalogue where solutions aimed at reducing excess noise span multiple domains and apps. Power delivery is one of these but exists alongside signal-related designs as part of a wider systemic perspective. The Firewall line emerged directly from holistic thinking. Conceived as a passive inline module, it intends to remove noise where current flows. Over time the Firewall range expanded whilst adhering to the same underlying framework, evolving into a broad family of accessories applied across different system contexts. Its current presence by way of products meant for internal and external use reflects LessLoss' view of noise as a pervasive and cumulative problem rather than something confined to an isolated scenario. That LessLoss approach noise with a single highly universal component is a conclusion reinforced by my repeated hands-on exposure to their Firewall range.
My point of reference with this approach dates back six years to a review of the Firewall 64x, a model long since discontinued. That encounter established familiarity with the underlying idea as a whole rather than any single application of it. Six years however are a long time in audio terms during which systems, environments, expectations and reviewer perspectives shift inevitably. Approaching the Firewall 640x Stellar now is less about revisiting a specific device and more about returning to an approach to noise rejection that continued to evolve. The 640x Stellar sits prominently within the catalogue as the most advanced expression of the company's long-running Firewall initiative. Filed under power conditioners, it follows a naming convention by now well entrenched in the industry and anything but cryptic. While the broader market tends to associate power conditioning with sizeable multi-outlet enclosures, the Firewall 640x Stellar once again pursues its objective by far more compact means: reducing unwanted electrical contamination before it has a chance to propagate across connected audio hardware. The goal itself is hardly controversial. The manner in which LessLoss pursue it very much is. Despite its elevated position in the lineup, the 640x Stellar remains visually understated and functionally direct. It arrives as a compact highly specialized plug-and-play inline cleanser that simply wants a power plug inserted into its IEC inlet, its umbilical connected to a component of choice and nothing more. This straightforward protocol leaves little room for interpretation, reinforcing the impression of a purpose-built tool rather than accessory designed to impress on appearance alone. The emphasis is clearly on internal execution and correct placement within the system, not ornamental excess. Previous Firewall 64x and 640x models employed solid Oak housings. Today's does not. LessLoss long advocated Panzerholz for its excellent self-damping properties. The Firewall 640x Stellar however is built from multiple extremely hard dense layers of resin-infused Kraft paper which I am told surpasses Panzerholz for mechanical noise suppression. In hand the device finished in a satin sheen feels unmistakably like a premium object. In practice it remains reasonably lightweight and poses no risk to a component's IEC inlet.
As with earlier Firewall products, the 640x Stellar was designed to operate quietly and out of sight, most likely behind a rack or near the point of power entry to a given component. LessLoss continue to advocate a distributed approach to noise management so multiple conditioning points not a single centralized device. In this sense the 640x Stellar is less an isolated product than part of a broader strategy, allowing users to scale their noise-reduction efforts in line with system complexity and ambition. If the financial aspect is not a limiting factor, numerous Firewalls can not only place in front of each active component in a system but connect one into another effectively without limits. The Firewall tech itself has been under continuous development for years and the 640x Stellar represents its most mature elaborate incarnation to date. At its heart is the company's proprietary skin-filtering concept devised to address high-frequency noise travelling along conductors rather than via conventional reactive elements. True to form, the Stellar operates passively with no active circuitry and adheres to the long-standing "no coils, no capacitors" philosophy that has become something of a company hallmark. While the underlying idea can be traced back to earlier products such as the DFPC power cables and first-generation Firewall implementations, this execution reflects a substantially revised technological base. In the 640x Stellar it takes the form of a compact module built around precisely arranged conductive structures embedded within a stable carrier which—according to the manufacturer—allows for significantly improved noise control compared to earlier approaches including ferrite-based solutions whilst ensuring that live, neutral and ground conductors are all conditioned alike.
While we don't know how many Firewall units hide inside today's satin enclosure, it is nonetheless fascinating to examine how they work and why. Copper rods housed within translucent resin structures undergo LessLoss's in-house Entropic processing. This treatment drastically accelerates the aging of these parts and results in their distinctive matte appearance. More importantly, it alters the conductor's internal structure, rendering it directional and far less susceptible to micro vibrations, hence quieter. That however is not the whole story. Entropy by definition describes gradual decline into unavoidable decay and this copper is pushed so far along that path that it becomes extremely soft. Think far beyond a human lifetime of constant use condensed into a matter of days through intensive processing. Left unsupported, these conductors would deform. The surrounding crystalline resin elements therefore serve a crucial role by locking the copper firmly in place, preserving its integrity and lending the entire assembly mechanical stability.
