A few words on the box supplemented with these photos. Dimensioned like a slightly tall but shallow paperback of Dune thickness, the matt black finish of the outer dress plates with its peekaboo clearance for the underlying brass frame is elegant. It also seems quite impervious to skin oils hence fingerprints. As the proverbial black box of mysterious guts, it very much looks and weighs the part. Photos don't convey the material density but it's high. I can already envisage the Echo's End DAC clad alike so its cosmetics pull even. This new look is a smooth and stylish operator.
Again, XLR4 i/o mandate having appropriate cabling.
If it wasn't clear already, FoH is a passive inline filter. It adapts the prior award-winning Firewall for Loudspeakers tech to headfi; and doubles as a preview for RCA/XLR line-level scenarios that will simply use different connectors and internal module allocations.
What's being filtered? UHF noise propagating on the outermost conductor surface. This phenomenon is called skin effect. Where does such noise originate? With switch-mode power of generic household appliances and hifi gear; with ever-increasing WiFi and Bluetooth exposure; as the radiation of high-speed digital processors. In casual lingo, the effect of such noise on the music signal is hash, grit, glare, edginess, metallic undertones and a hazing of planktonic detail. It's just not noise we hear as noise like a buzzing transformer, ground loop, crackling tubes, dust pops on vinyl or power-supply hum in a midrange. It's the intermodulation effects such out-of-band noise has on the audible spectrum which become observable in a direct comparison with—effective!—such noise filters. Typically that effect is a diminution of the aforementioned attributes. Less edge can translate into more smoothness. Less glare becomes more darkness. Less obscuration of micro detail can reveal more ambient data, even greater timbre differentiation when more ultra-fine upper harmonics rise above the noise floor. Digital engineers mention how such noise loads up computing processes. They become less efficient, potentially prone to more errors or having to invoke more error correction protocols. Inserted at the tail end of the signal path just ahead of the transducer which converts signal voltage and current to mechanical motion, FoH seemingly can't lower stress on digital processes when its focus is the purity of already amplified 'final' analog signal. Or can it?
The ribbed makeup of these 16 copper sections seriously increases their surface area for the intended passive skin-filtering effect.
"An argument can be made that our Firewalls lower jitter in DACs even on analog signal lines because they as well as power lines act as antennae plugged into sensitive DAC circuitry. Corrupted power corrupts signal creation in real time but corrupted signal lines add corruption to ever so slightly late-occurring signal creation in source schematics. Just because the signal goes 'out' doesn't mean noise can't go 'in' as in the end all picked-up stray signal gets into circuitry due to antennae effects. Headphone cable can be seen as an antenna and the Firewall lowers noise regardless of direction. So both load and source benefit." Words and photos from the designer's bench.
2.3mm² x 4, cryo and Entropic process.
Meanwhile the new supplier of production C-MARC headfi cables had dispatched a 1m XLR4 leash for my Susvara and included the short 6.3mm|XLR4 cable he'd made for Dawid's review. That would connect to the ¼"-only AMP-23R from Enleum. Louis' above cable would serve the XLR4 outputs of my Kinki THR-1 and Cen.Grand Silver Fox. About the nomenclature of the Susvara cable, "I have a few names in mind but haven't decided yet. The base price for a 1.5m C-MARC headphone cable should be ~€1'250." By separate post from sunny Palma de Mallorca, the DHS-1 convertible headphone was inbound. And Linear Tube Audio's Velo 6SN7 head amp with 6.3mm output was still on hand from its feature review. I could play musical chairs up and down the stairs and really give FoH the interface runaround.
