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To assess the HPA's performance into headphones, I juxtaposed it with the Aussie Burson Audio HA-160 [$699 and €499 delivered to the US and EU respectively]; and the Taiwanese HeadQuarters from KingRex [$890]. Both those are competing and quite affordable transistor designs. They ran off the HPA's fixed outputs because Vinnie's unit lacks an analog input. Its internal DAC cannot be bypassed. Meanwhile the other amps lacked their own internal DACs. This was the only scenario in which each amp would see the same front end.

Sources were uncompressed streaming files from my iPod Classic 160GB through the Wadia iDock; and conventional RedBook data extracted by laser from Raysonic's massive two-chassis CD228 used just as spinner. The digital cable was an older true 75-ohm Chris Sommovigo design.

Headphones included AKG's K-702 with custom ALO Audio harness, audio-technica's W5000 'Raffinato', Grado's PS1000 and Sennheiser's HD800 with ALO harness. Their reviews detail out sonics for further context.

To judge the Isabellina converter separately, I moved it into the big rig. There it went against my Yamamoto YDA-01 zero-feedback single-ended transistor DAC; and the externally accessible valve-powered converter of AMR's new CD-777. The latter uses a "Philips UDA1305AT multi-bit chip set which from AMR's analysis of the design and sonic performance of converters is the closest to the TDA 1541A. The UDA1305AT is also superior to the TDA1543 and TDA1545."

Unlike Vinnie's no-sampling implementation, AMR's design team lets the user choose from four upsampling and filter modes - plus zero sampling and zero sampling with treble compensation. The last setting is dubbed Master II. It would make for the most interesting comparison. It's well-known after all that traditional Kusonoki-style conversion as implemented in the HPA rolls off the top end and softens the transients. AMR has the antidote, RWA does not.

RWA | Burson: Despite a significant price discrepancy which to some might step outside the DAC inclusion of the HPA, these amps were cut from a conceptually similar cloth in that both produced a big, full and meaty sound closer to tubes than transistors on image density and mass but clearly transistorized on greater 'textural damping' than valves. But there were significant differences too. The HA-160 was the clearly more informative, extended and resolved in the upper regions. The HPA was soft and recessed by comparison. This extended into a perception of greater overall relaxation and cuddliness. It had the Red Wine Audio unit sound mellower and 'slower', the Australian as though it had fiercer drive, greater propulsion power and gathered the tunes together tighter. Both were a draw on bass heft and reach, e.g. absolutely first rate and maximized. The Burson seemed to stage even broader particularly over the HD800s, likely because fine ambient reflections—on those recording which actually had them—were more apparent. In terms of conveying musical excitement, inner tension and harmonic resolution, the half-priced Burson (the HPA without DAC is $1.500) clearly had the upper hand yet didn't give up anything in trade. With its discrete low-noise super regulators, it was just as quiet and its class A bias imparted that minor sweetness typical of the breed. As though that weren't enough, it sports a solid 6-mill aluminum tank casing, then adds a custom stepped pot which inserts a single resistor per level per channel into the signal path.

RWA | KingRex: Sonically this was a replay of the above but to not quite the same extent. Once again the top end illuminated as though a cloud evaporated each time the Taiwanese served; image outlines snapped to attention; and the mellifluousness of the HPA went as though to a workout for greater striations. This soft/round trait of the RWA is very tacit. It takes no time to hear. It's a clear and deliberate choice or preference which the designer imprinted on his work. Hence inherently mellower 'phones like the Raffinatos become a like-meets-like proposition. It makes these traits even more pronounced. It does avoid polite however. To seem polite relies on a bit of emasculation. The HPA's ballsiness in the nether regions, its potent image density and lively dynamics simply won't go there.

KingRex | Burson: Triangulating earlier impressions, both clocked higher on the excitement scale, on raw quantity of data and on finesse of tone modulations than the Isabellina HPA. All things considered however, the contender from Oz struck me as the aurally most complete and advanced. Without veering into the tipped up, its visibility was the greatest, its upper bands the most worked out. Yet this didn't steal one cent from embodiment or the resolved warmth that arises with tonal fullness but remains divorced from the inner limpidness and lowered tonal center which are the trademark of the HPA. Invoking price and build + parts quality, the chunky silver box from Oz really upset this apple cart. It walked off with the most persuasive performance and screamiest value. Incidentally, all three amps weren't exactly hasty during break-in. Premature nuptials will end in disappointments. Be patient and clock those hours.

To me ears and from my quartet, the best 'phones for the Isabellina HPA were the AKGs and Sennheisers, i.e. the two without any inbuilt warmth but very high magnification power. They handled and even benefited from Red Wine's voicing without taking too great a hit in airiness. Those who run the HD800 off its 36-gauge stock leash are in fact predestined to consider the HPA a match made in heaven. Sennheiser's tonal balance will cast lower anchor, their somewhat skittish top end relax. I wasn't surprised to learn that this particular combination is popular and enjoys positive forum comments. Rightfully so. It's quite the hammer.

What a dedicated headphone amp of the HPA's caliber demonstrates are wider headstages which don't occur just inside the skull but seem to extend outwards a bit to include the ears and wrap around the occipital. Just to what extent depends on the headphones of course. Some are more endowed than others. But even the smallest stager expands with quality amplification. AKG's K-702s aren't the greatest in that regard but rather less restricted once fronted by the HPA.

Otherwise—and no surprise considering—the HPA adopts the signature Red Wine Audio house sound which I previously encountered with the 30.2 Signature T amp and Isabella preamp. It's relaxed but not sleepy, powerful yet soft, more concerned with organic flow than angular attacks, about round comfort and not spiky stress, mass and not greased reflexes. It's not about extreme resolution or adrenaline-charged excitement either.

Because much modern hifi veers to deeply into that direction—take the Tim Roth Fox television series Lie To Me as a visual stand-in for this trend and compare it to the older Inspector Morse or its Lewis spin-off—Vinnie's consistent voicing is a very effective antidote. If your system is properly dialed for deep resolution however—benign resolution, not trying hyper stimulation—this voicing is clearly a step backwards. Then something like Burson Audio's HA-160 becomes the right step forward.

This story continued in the big rig which at that moment consisted of the Boenicke Audio SLS powered from a FirstWatt J2 on top and April Music's Stello Ai500 on the bottom. My Yamamoto converter was patently more resolved, more astute on the attacks and capable of deeper penetration into the far recesses of the stage where the tiny stuff happens. It was also more lithe and lit from within and had a more informative grasp on harmonic shifts and turns particularly on stringed instruments. The RWA once again was denser, weightier and darker. Which of the two would be more appropriate depends on the context and listener of course. In general, Vinnie Rossi's approach better fits beginners whose systems err on the side of roughness. They need to be made more civilized and smooth. Components like the Yamamoto apply greater magnification power which is required for advanced systems but also involves more of a tight-rope walk. RWA's recipe isn't just easy sound, it's also easier to implement and doesn't present as many possible pit falls for failure.

The gap between the AMR in Master II mode and RWA converters was a lot smaller. The former was a bit slimmer in the midrange but retained somewhat stronger treble presence. Unexpectedly its 6922s did not contribute any overt traits which would have clearly set apart this British machine from the American or telegraphed the presence of glowing bits. What really separated these D/A converters were single-digit percentage points of very narrow distinction. Clearly shared aspects were relaxation/ease and high image density for proper fleshiness. Within this sector of 'vintage' sound, AMR's incorporated greater modernization by restoring subtly more treble energy. Hence I thought it slightly more advanced, never mind radically more flexible by offering a total of six on-the-fly 'digital math' settings which can morph the presentation deeper into the sharper-edged realms.

Enter the calculator: Red Wine Audio started as a low-budget brand which sold direct. Dealers and distributors signed up later and the line went a bit more upmarket to absorb the concomitant price increases. At $2.000 for the Isabellina DAC sans headphone module (and $1.500 with USB stripped as well), competing designs today offer more resolution and arrive in fancier casings. At the least, RWA seems due for a cosmetic makeover. Some might even say that their very friendly house sound could benefit from the next round of refinements to include more aeration, less damped upper harmonics and superior inter-note transparency. If so, AMR's work on the NOS scheme bears investigation. Or, the future could be with ultra-modern chips.

The general value equation heats up seriously when we consider the headphone application. With the latest precedent set by the Burson blokes, one doesn't just obtain the 'next-generation' RWA sound already today. One gets it packaged in a fancier enclosure for a lot less less money and not from Vinnie Rossi. That's food for thought.

: Vinnie Rossi's back-packing bat—the ability to run another low-draw component off the HPA's internal battery—deserves another mention particularly for the Wadia and Onkyo iPod docks. Converting the iPod into a fully legitimate audiophile music server by tapping its uncompressed files digitally is clearly the future. Piggybacking a 'digitized' iPod atop Red Wine's headphone amplifier is very convenient and moves the lot on the patio, balcony or poolside without worrying about AC outlets. The next logical step then becomes what Peachtree Audio's iDecco has already accomplished. It's 'hard-wiring' a converter's iPod cradle directly to its internal chip. This eliminates that silly additional—and mostly empty and thus essentially redundant—box Wadia & Co. expect us to buy at present.

Think HPA with integral iPod cradle. That would really put it all in one enclosure. Naturally, Apple certification could exceed RWA's resources. But it's not only a thought, as a trend it's really inevitable and big corporate like TEAC is already there.

• Typically Red Wine Audio.
• If you've read one RWA review, you've read 'em all.
• What else is new?

Such could be your reaction right now. That doesn't make the underlying fact any less real. The Isabellina headphone amplifier sounds exactly as expected given prior exposure to the brand. It also looks it. In short, there are no surprises except that despite the firm's admirable price reductions, the latest competition from abroad has turned up the heat once more. Disregarding that, the Isabellina HPA is for those who value smoothness with mass, warmth and wallop. This is a long player that won't fatigue even at high volumes and over long stretches. It's quite the recipe for a lot of popular modern music that's not recorded too - um, hot. Where certain hifi gear makes no concessions, this machine does. That earns it no trophies for being able to hear which leg was arthritic on the fly that just landed on the tone arm (I kid you not, that verbatim was what one turntable manufacturer once proudly told me his setup had achieved). But it's eminently relevant in the real world where folks hope to enjoy all of their music and not just a small audiophile-approved section which steadily shrinks as their audio investitures increase and their components improve. If this describes you; and you're not just about the absolutely steepest value for money; and not too concerned with pushing your system too far uphill into the sun-lit areas where each minor misstep telegraphs brutally - then the black box from Durham/Connecticut is another slam dunk from the go-off-the-grid company.
Quality of packing: Ensconced in ultra-thick foam inside an inner carton inside a cardboard outer. Essentially idiot-proof.
Reusability of packing: Many times.
Condition of component received: Flawless.
Completeness of delivery: Perfect.
Website comments: Easy to navigate, very informative.
Human interactions: Always prompt and friendly.
Pricing: No longer quite the value which was synonymous with this brand in the early days.
Final comments & suggestions: An analog input would be nice for those who already own one source that's superior to the internal DAC. Relocating the digital input selector to the front would make it more convenient.

Red Wine Audio website