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John Grandberg
Last time out, I detailed four ‘starting point’ headphone amplifiers, all of which performed admirably for their relatively low asking price. From the diminutive Pro-Ject Head Box S2, to the potent Schiit Asgard 3, the ultra-precise Drop + THX AAA 789, and the seductive Feliks Audio Echo, we learnt that we don’t have to spend a fortune to achieve respectable performance from a headphone setup.
That four-part assignment made the case for moving to a dedicated headphone amplifier rather than counting on the headphone output internalised in a DAC, pre-amplifier or smartphone. That said, higher performance tiers do exist and are worth exploring here so that more demanding listeners can investigate further.
I have once again gathered four current headphone amplifiers but at higher price points: ranging from US$1350 to US$3000 and split 50/50 between tube and solid-state. Although we can still spend quite a bit more on a headphone amplifier, I think of this level as “mainstream” high-end where we find more complex designs and higher-quality parts.
It’s worth noting that the rest of the chain must be sufficiently resolving to justify any move to this segment. That means transport, DAC, ancillaries, and – of course – the headphones should all be well sorted. If not, the sonic gains over my original group of four budget amps might not be felt. Get it right though, and these headphone amplifiers can really bring a system to the next level.
My initial roundup used Pro-Ject’s Head Box S2 as a baseline. We’ll do the same here. The Austrian manufacturer’s Head Box DS2 B sells for US$600 – US$700 depending on finish. Basic black is the most affordable option, with silver available for an upcharge. More visually interesting is the option for real wood side panels (eucalyptus or walnut).
My review sample came in silver with the walnut trim and I feel the wood really sets things off aesthetically. Audio gear, particularly at this level, should not only sound great but also have visual appeal, and to my eyes, the wood accents pull that off far better than monochromatic metal alone.
You might be wondering: “Isn’t the Pro-Ject close to the pricing of the first batch of amplifiers?” Indeed it is. But remember: the Head Box S2 displayed a noticeable jump in performance when paired with its matching Power Box S2, with pricing moving from “the most affordable” to “still within range” for that group.
We find a similar situation with the Head Box DS2 B when paired with its matching Power Box DS2 Sourceslinear power supply. This time around, however, the jump in sound quality is even greater. The upgraded power supply goes for US$650-750, depending on its configuration.
The combination of amplifier and power supply clocks in at US$1250 and tops out at $1450, meaning Pro-Ject once again offers the most affordable entry in this upfield moving group.
The “B” in DS2 B presumably stands for “balanced”: this is a fully balanced, dual-mono design with XLR inputs (and bypass outputs) on the back panel plus a 4-pin XLR balanced headphone output on the front. Single-ended inputs and outputs are provided for convenience but you really want to go fully balanced to make the most of this device. Pro-Ject lists output from the 4-pin XLR as 1100mW into 33 Ohms which is certainly more potent than the little Head Box S2.
Meanwhile, the Power Box DS2 Sources is quite heavy for its compact size (3.4kg). It features a massive toroidal transformer and generous filtering capacitance for smooth, low ripple power delivery. It provides 5 outputs total, split between 9v, 15v, and 18v, making it a suitable dance partner for a variety of Pro-Ject source gear – hence the word “Sources” in the name. One could thus feed a matching Pro-Ject turntable, streamer, CD player, and DAC, plus the DS2 B headphone amplifier all from this same power supply, delivering a performance boost all around. That’s value.
To be clear: the Head Box DS2 B is a perfectly capable unit with the stock power supply. It actually falls right in line as an upgrade to the Head Box S2/Power Box S2 combo. That means we hear an even-handed response, well-controlled treble, solid low-end extension, and reasonably accurate imaging. All well and good, but we have loftier goals for this roundup… and the Power Box DS2 Sources brings the experience to an entirely higher level.
The duo sounds tonally richer than the amplifier flying solo, giving us a more convincing sense of weight and scale. It also has a distinctly blacker background, with transients emerging from the void with remarkable clarity. This results in more accurate imaging whilst revealing layering that would otherwise be glossed over on stock power. Treble extension feels subtly improved and low-end texture more refined – it, therefore, feels like it kicks harder, even if there really isn’t more bass. As a gatekeeper into the realm of high-performance headphone amplification, the DS2 combo sets the standard.
While I loved the simplicity of the Head Box S2, the DS2 B ends up being more versatile thanks to adjustable front-panel controls. Users can select low, medium, or high current output, along with their choice of 4 gain settings – mix ‘n match for best results depending on the headphone being driven. I found the lowest current setting was very capable of driving sensitive IEMs with no spurious background noise. The medium setting was usually ideal for dynamic headphones. Planar magnetic designs seem to soak up current, so the highest option is typically best for them. Gain settings vary based on the incoming signal – lower choices will compensate for a source with hot outputs, whilst something like a Resonessence Labs Concero DAC (which gives a below-standard 1.2Vrms signal) will benefit from the higher gain settings.
Though Pro-Ject’s wood-clad duo is a solid performer with a variety of headphones, my favorite pairing ended up being an AKG K812 which has been rewired and modified for balanced operation. Listening to Australian folk-pop siblings Angus & Julia Stone’s Down the Way showcases rich midrange tonality and delicate treble response, whilst Lemaitre’s catchy electro-pop comes through as lively and dynamic. The system is detailed enough to beautifully portray Sophie Milman’s “audiophile approved” jazz standards yet can handle the low-fi indie rock of Lo Tom without sounding overly flat. It really is an amplifier with universal appeal.
To sum things up with a crude car analogy: the Pro-Ject Head Box DS2 B with stock power supply reminds me of an entry-level BMW 3 series sedan. The general competence of the platform cannot be denied, even if it doesn’t quite push the performance envelope in any particular way. It’s just solid transportation which still manages to have enthusiast appeal. Adding the Power Box DS2 Sources transforms it into a fire-breathing BMW M3 worthy of hanging with the big boys. Can it still be outclassed by bigger, badder, and more expensive competition? Sure. But many will not want – or need – anything more.
Further information: Pro-Ject
Next up, the SparkoS Labs Aries.
