Pro-Ject Head Box DS2 B Headphone Amplifier Review

The demand for high quality audio is on the rise, as is the demand for high-quality audio in a smaller form factor than that offered by traditional separates. While smaller systems do of course exist, they don’t typically offer the quality one can expect from a traditional system and are at best a compromise. Pro-Ject’s Box Design range aims to fill that gap, offering a range of products to suit almost any system and budget. The latest in the Box Design range are the nine-strong line of DS2 products which includes both analogue and digital preamplifiers, mono and stereo power amplifiers, a CD transport, a DAC, a pair of phono stages and a headphone amplifier – the HeadBox DS2 B.

We recently gave the Phono Box DS2 USB a wholehearted and thoroughly deserved recommendation, giving the Head Box DS2 B a lot to live up to. The two units are physically similar and share a similar compact (206 x 218 x 70 mm (w x d x h)) casework of either a metal / aluminium sandwich construction or finished with walnut or eucalyptus side panels. Those side panels raise the dimensions to 240 x 218 x 72 mm (W x D x H), but the difference is marginal and the units retain a sleek modern appearance with a touch of retro charm.

Pro-Ject HeadBox DS2B Black Eucalyptus

Inside sits a dual mono circuit based around a pair of TPA6120A chips, capable of delivering 250MW, 550MW and 290MW into an 8Ω, 33Ω and 300Ω load respectively. Signal to noise is rated at 98dB (at full output), with a frequency response of 20Hz – 20kHz flat to within 0.2dB, suggesting a neutral, uncoloured presentation. Volume control is analogue and based around an Alps Blue control, with muting and switching relays used throughout to minimise crosstalk.

The front hosts a volume knob along with small push-button controls for gain, current, input selection and standby, the latter complete with the seemingly obligatory blue LED. The gain can be set in four steps – 0dB, 3dB, 9dB or 12dB for unbalanced inputs, and 6dB, 9dB, 15dB and 18dB for balanced inputs. The current setting allows the output current of the amplifier to be alternated between 3 settings – high, mid and low – depending on the load you’re driving and the power desired.

The Head Box DS2 B provides both balanced and unbalanced outputs in the form of 4-Pin XLR and 6.3 mm quarter inch jacks respectively. These are matched by both balanced (XLR) and unbalanced (RCA) inputs on the rear panel, the latter converted to balanced signals at the input stage by a phase inversion circuit. The rear also offers both balanced and unbalanced bypass outputs. These allow the signal input to the headphone amplifier to be output to a recording device or another amplifier, useful if you’re using the HeadBox DS2B with an integrated amplifier or preamp with only a single line level output. This is a very welcome feature and one that I wish other manufactures included.

Pro-Ject HeadBox DS2B Rear

Supplied with the Head Box DS2 B is an 18V, 1A DC power supply with a set of country-specific outlet adapters. As with the Phono Box the power supply is a cheap affaire that doesn’t inspire confidence and doesn’t belong with a unit of this price and quality. It works and doesn’t appear to have any adverse affect on the sound of the unit, but it does emit some audible switching noise and even a better switching supply would have been preferable. A well made switching power supply needn’t cost the earth and will be more than adequate in this application, so seeing a better model included would be welcome.

Pro-Ject HeadBox DS2B Silver Walnut

The Head Box DS2 B was connected to the balanced outputs of my Cambridge 851N streamer, and to the RCA line outputs of my Marantz PM-11S3 amplifier so as to use its phono stage and input switching for other sources. The balanced bypass outputs of the Head Box were connected to the PM-11 to enable the streamer to be used with the amplifier. I could hear no degradation in audio quality when using the bypass outputs. Headphones were a mix of Sennheiser HD202s, HD650s, HD800s and a couple of studio models from Yamaha and AKG all of which the DS2 B drove effortlessly with gain and current settings adjusted to suit.

Sound wise the Head Box DS2 B displays an abundance of power and an ability to drive any load with ease. The noise floor is as good as inaudible even when idling at maximum volume with current and gain on high. Stereo imaging is about as good as it gets and the amp doesn’t strain when pushed – it simply remains composed and powerful, never becoming harsh or fatiguing.

Perhaps the Head Box’s biggest trait is musicality. Pro-Ject seem to voice their products to approach the typical ‘valve sound, ‘ (one of liquidity and warmth) – a sound that I am fond of but often dismiss because of the lack of reliability and maintenance required when running a vacuum tube-based component. Though entirely solid state, I could listen to this amp long into the night – as I in fact did on many occasions, resulting in a delay in publishing this review. Its low end performance in particular is astonishing – so powerful and well controlled – but the top end is brimming with detail. I don’t wish to enter the realm of audiophile cliches, so suffice it to say that fed by a good source the Head Box DS2 B reaches a point where the law of diminishing returns kicks in. Headphone performance doesn’t get much if any better than this.

To summarise, the Head Box DS2 B is another outstanding product from Pro-Ject. It’s packed with a number of useful features missing from the competition such as the bypass outputs, the ability to run balanced headphones and an array of adjustments to suit any pair of phones. My only wish would be to see remote volume control. As the Alps Blue is a motorised pot this would likely be neither difficult nor costly to implement. That aside, the HeadBox DS2 B is an extremely capable amplifier and I give it a thoroughly deserved recommendation.

By Ashley

I founded Audio Appraisal a few years ago and continue to regularly update it with fresh content. An avid vinyl collector and coffee addict, I can often be found at a workbench tinkering with a faulty electronic device, tweaking a turntable to extract the last bit of detail from those tiny grooves in the plastic stuff, or relaxing in front of the hi-fi with a good album. A musician, occasional producer and sound engineer, other hobbies include software programming, web development, long walks and occasional DIY. Follow @ashleycox2


    1. It should work with any DC power supply providing it outputs 18V and has a current capability of at least 1A. Pro-Ject themselves manufacture a linear power supply range but any will be fine providing the polarity matches. There is a data sheet for the amp chip Here.

  1. Hi,

    Thanks for the review! I’m interested in this amp.

    Do you think a HQ separate headphone amp, like the DS2B, is better than an integrated one in a HQ stereo amp? Or is it meant to be an upgrade to a mid-fi system?

    I have the Cambridge 851 N-E-W setup and I’m satisfied with the headphone output on the 851E, but I haven’t compared it to a separate headphone amp. I think I read on the site somewhere that you used to own 851 E/W, and you still seem to have the 851N. Do you think that the headphone amp in 851E is on par with the DS2B?

    Also, I’m curious what the so called “balanced” headphones output of the DS2B can do to sound quality. I realize it’s not really balanced like a connection between amps (you would need 3 conductors for each channel to cancel out interference). But 2 dedicated conductors for each channel means there’s no joint ground, which could be beneficial.

    I just wonder, if this means an improvement, even the slightest, why isn’t it more common? It seems so easy they could have done it in the 70s. There must have been a reason they opted for joint ground instead?

    1. The HeadBox is an upgrade on the headphone out of the 851E, though whether you’ll notice the difference depends on the headphones you’re using as the 851E headphone output really is rather good. You also lose the convenience of remote volume control. That said if you’re running particularly revealing headphones, or power hungry headphones of 300 ohm impedance or more, then yes the upgrade is worthwhile in my opinion.

      As for balanced headphones; yes there is a difference for the better, but it’s not always night and day. Some manufacturers did incorporate balanced headphone outputs in the ’70s, even on cheap all-in-one systems. I think Philips did it and I have a vague recollection that ITT did too but don’t quote me on that. I suppose ultimately the jack takes up less space and looks nicer, and is easier to miniaturise and adapt for portable devices.

      1. Thanks for your answer. I plan to upgrade my headphones within a couple of months, so I’ll try to evaluate some “balanced” ones for comparison. I’m also curious to compare the HeadBox to my 851E.

        But, I have been thinking about the lack of remote control… Since I’m so used to having a remote for the 851E, I think it would be too hard for me to adjust to being without one. What were Pro-Ject thinking when they didn’t include this elementary feature…

        1. Most headphone amps lack a remote control, I can’t think of any off the top of my head that have one. You could always run a cable from the RCA preamp outputs of your 851E into the Head Box, set the Head Box volume to almost full and you’d then be able to use the 851E as the volume control. You’d just have to turn the power amp off when you wanted to use headphones. As for balanced headphones, for most mid to high end headphones with detachable cables, you will find that there are balanced cables available either officially from the manufacturer or aftermarket. SO even if a headphone doesn’t advertise balanced connectivity as an option, that doesn’t mean it’s not possible to run it balanced if you so desire.

          1. I think I’ve seen a remote control on some Beyerdynamic headphone amp, but you’re right that it’s rare. It seems to be more common though on the DAC/Headphone amp combos.

            Using the preamp out connection from 851E to the HeadBox – doesn’t it degrade the audio quality a bit, using two volume controls in conjunction?

            I’ll be looking for the detachable cables, thanks for the tip!

Share Your Thoughts

Discover more from Audio Appraisal

Subscribe now to keep reading and get access to the full archive.

Continue reading