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Fostex HP-A3 DAC and Headphone Amp

Headphones — are they my cup of tea?

My relationship with headphones and associated equipment has been pretty hit-and-miss over the years. Headphone listening has always been a definite second choice – relegated to late-night listening so as not to disturb my partner, or when away from home. Plus, I find most headphones uncomfortable to wear, so spending money on a high-end – or even half-decent – headphone rig never made much sense to me, and earlier forays into this area have fallen somewhat flat.

Nonetheless, I decided last year, after finally getting around to ripping my music library, to obtain a reasonably-listenable headphone setup using a computer as the source. After some looking around, I purchased a pair of Sennheiser HD-598 headphones and an Audio-GD NFB-12 DAC/headphone amplifier. The Sennheisers (around AUD300), I am happy with for the price; the Audio-GD (USD200 plus shipping)… not so much. It worked OK, but it sounded closed-in and a bit strained, even when fed with a 96 kHz signal from Pure Music. Long story short, I recently realized that I needed to find something that I like listening to, as my partner’s work schedule was about to mean more time with the phones. DIY was, as usual, considered, but adding a new project to an already-long list wasn’t looking like a great idea.

So, I read around again, and then headed off to the offices of retailer Wicked Digital in Sydney’s Lower North Shore, together with my laptop, the Sennheisers, and the Audio-GD for comparison purposes, to try out the new Calyx Coffee (AUD300). With a Sabre DAC chip, 24/96 capability, and an asynchronous USB interface, the Calyx ticked all of the “buzzword-compliance” boxes. Steve Lees (the proprietor) was kind enough to let me set up camp with my laptop, phones, and the DAC/amps connected in between, and I proceeded to listen to a selection of tracks from the small library on my laptop. Alas: while the detail and clarity of the little Coffee impressed at first, I gradually came to realize that the Calyx and I were not going to be tying the knot that day. The pre-emptive annulment was abruptly finalized when I caught myself wondering if EQ would take the edge off it.

Ouch. Well, since I had already driven all the way there, it wasn’t going to cost me anything to listen to something else. Half an hour later, I walked out with a Fostex HP-A3. I was surprised, and I think Steve might have been too. I had never heard of the Fostex amp before – in fact, I didn’t know that Fostex made headphone amps. Not a lot of forum buzz on that one then. This segment of the market is getting very crowded, so one option would have been to spend another week or two painstakingly researching everything I could find. Thing is, though, I often find that – for a given context and purpose – an item of gear is simply either good enough or it isn’t, and in this case the Fostex handily made the grade, giving an initial impression of delightfully clean mids and of being tonally well-balanced. At AUD449, it’s admittedly twice the price of the Audio-GD; but, I liked the way it sounded, so that was that. Plus, the fact that the Fostex is USB-powered would enable the headphone rig to be properly portable.

Fostex HP-A3 DAC and headphone amp, with Sennheiser HD-598

Fostex HP-A3 DAC and headphone amp, with Sennheiser HD-598

Listening impressions

The evening that I returned home with this diminutive unit was spent flicking through the archives of my music collection at my desktop machine, trying this, that, and the other, including stuff I hadn’t listened to in years. I found myself getting (somewhat) ballistic à la Peter Garrett to Stand in Line from the Oils’ second album Head Injuries; grooving out to the Grace Jones of University-era block parties with Pull up to the Bumper Baby; and inexplicably (very) doing the choo-choo to Linda Ronstadt’s rendition of Chuck Berry’s Back in the U.S.A. OK, I admit it – I got a little over-excited. But the takeaway from this is that the Fostex has rhythm – albeit more of a measured rhythm than a headlong rush, that some may call laid-back. The amp delivered a solid bass performance – more than I thought the Senns had in them – and a compelling soundstage. There was no “left-right-center” effect here – where the recording called for it, I was met with a solid wall of sound.

With the initial excitement over, I resolved to take a more leisurely pace and listen to more contemplative music. There are two reasons for this, one being that late-night listening also implies more relaxed fare; and the other that I doubt the wisdom of spending a lot of time using headphones to listen to music that requires “slam” or “punch” to best appreciate, as the lack of a physical impact means that one can easily be listening at higher levels than realized. So, I connected the amp to my laptop again and placed it next to a comfy chair in the living room. I used Pure Music and Audirvana Plus for subsequent listening.

In the ensuing days, I found that, for the most part, the Fostex rendered solo instruments with palpability and realism. In Part II of Jarrett’s La Scala, the full scale of the keyboard, from the thumping extreme left hand work to the delicate runs across the right are captured perfectly, with Jarret’s pedal (I assume) thumps and vocalizations laid over them towards the right. Peter Wispelwey’s rendition of the Bach Cello Suites is wonderfully lyrical, although perhaps too closely-mic’ed to deliver a believable image of a physical instrument through headphones. With solo classical guitar, again, an enticing palpability and sweetness from John Williams’ Classic Williams, Romance of the Guitar. On steel strings, though, Tommy Emmanuel’s Only sounded a little less coherent, with the finger strikes and the reverberation from the body and strings not quite integrated into a sense of a single instrument on a couple of tracks.

Moving on up to small ensembles, Nigel Kennedy and Lynn Harell delivered a vibrant, energetic, performance in the flatly-named Duos for Violin and Cello. For something more unusual, Triology’s Around the World in 77 Minutes presented well the interplay between the violin, viola, and cello, with its unusual use of pizzicato, strumming, and vocals. In keeping with the general theme of the last three paragraphs, the Fostex allowed me to just sit back, close my eyes, and listen to the music. With more complex polyphonies, though, such as baroque chamber, there is a slight lack of treble coherence that becomes apparent at times, as I noted with the Tommy Emmanuel guitar.

The other weakness noted at times was that, while the bass was generally deep and well-controlled and worked very well with classical, I can easily see that many would prefer electric bass to be tighter and more precise. There was a sense at times that it was a little slow to respond, and at other times, a slight resonance in the mid-bass that gave a sense of looseness. I attribute this in large part to the Sennheisers, and perhaps also to the fact that the Fostex is, after all, only running off a paltry 5V USB power supply.

I feel, though, that I am really starting to split hairs at this price point, as the combo continued to deliver a musical and engaging experience as I worked though more of my collection. I mentioned earlier the “wall of sound” on rock, and the ability of the amp to deliver a broad and even soundstage continued to impress. On the ironic Carol Brown from the Flight of the Conchord’s You Think I’m Freaky, for example, the delightful backing “choir of my ex-girlfriends” are positioned wonderfully in space to the left and right of Jermaine’s voice. On the Juilliard String Quartet’s The Art of Fugue, placement of the four instruments gave at times the impression of not only left-to-right positioning, but also in depth and height.

Other features

I’ve not, to this point, spent any time discussing the HP-A3’s features. There’s not really a lot to talk about, as it’s mostly “plug and play.” One point worthy of note is that the USB input accepts 96 kHz only, so you will need a source/player that can upsample to that rate.  I can only assume that Fostex chose to optimize the performance at 96 kHz and were able to do that best by not supporting other sample rates. On the Mac, iTunes, Pure Music, Fidelia, Audirvana Plus, and Decibel will all perform the required sample-rate conversion for files in the 16-bit / 44.1 kHz CD format. Amarra, however, does not do realtime sample-rate conversion, so can’t be used with the Fostex, except by doing offline conversion to the higher sample rate.

Fostex HP-A3 DAC and headphone amp, rear panel

Fostex HP-A3 DAC and headphone amp, rear panel

Apart from the USB input, there is a TOSLINK input, which is specified to accept a range of sample rates up to 96 kHz, and a TOSLINK output, which I believe outputs at the same rate as received. I did not try the TOSLINK output, but I did try the TOSLINK input by connecting it to an Apple TV (2nd generation), which upsamples 44.1 kHz material to 48 kHz. With iTunes on my main music computer (a 2011 Mac Mini) sending the signal to the Apple TV over the wireless network, and a USB power supply connected to the USB input, the system gave a credible performance although a notch below the direct USB/96 kHz connection. Some examples of the differences were some delicacy lost from Rickie Lee Jones’ voice in The Ballad of the Sad Young Men, and the background reverb on the snare in Holly Cole’s I Can See Clearly Now.

Physically, the Fostex is fine but not really a head-turner, with a simple folded steel chassis instead of the milled aluminium that seems to be so popular these days… I think of it as a plain Jane with a heart of gold. The volume control knob has a nice indent on it, so you can tell where it is by feel. In addition to the switch to select TOSLINK or USB input, there is also a switch to direct the output to either the headphone socket or to a pair of RCA jacks on the back. The volume control knob does control the level at the RCA outputs, so in a small system it could double as a preamp.

An aside on laptop listening

I do have to comment on a couple of drawbacks of the setup with a laptop used as a “music server.” These are nothing to do with the Fostex, but put a slight damper on the possible perfection of this particular type of portable audio system. The first is that, with Pure Music running a dithered volume control and up-sampling to 96 kHz, Activity Meter showed the PM process with a constant 32% CPU utilization, with the result that the laptop, a 2010 11″ Macbook Air, warmed up, making the lap position less comfortable. The fan came on once as well – I must have been doing something else CPU-intensive at the same time – thus creating background noise that marred the listening experience. Audirvana Plus was better in this regard, as it does the upsampling when loading each track into memory, thus reducing CPU load for the rest of the track.

The second drawback is that certain types of operation, like loading and saving files with some programs, would sometimes result in a small glitch in playback. If you read anything much about music servers, you’ll know that they are often “optimized” by removing any activity that isn’t directly contributing to music playback. Without going into the why’s and wherefore’s, it is possible that a more powerful laptop might not exhibit this behavior. Or, I suppose I could just not do work while listening to music – an appealing idea. For those looking for a non-laptop-dependent solution (and willing to pay more), the Fostex HP-P1 may be of interest.

Concluding remarks

With some relatively minor weaknesses noted, the combination of the Fostex and the Sennheisers get it right tonally, topped with those enticingly clean clear mids and an engaging sense of rhythm. Perhaps not the last word in resolution, but they are after all barely in the middle tier of (hifi) headphone gear in terms of price. For the simple pleasure of listening to music, the Fostex has taken my little headphone rig from avoidable to desirable.

Associated Equipment


Digital Inputs and Outputs

  • USB input: 16-24 bit / 96 kHz
  • Optical (TOSLINK) input and output: 32 kHz – 96 kHz

Headphone Output

  • Max Output: 100 mW (32-ohm loaded)
  • THD: less than 0.01% at 1 kHz, 32-ohm loaded, 100 mW
  • Frequency response: 20 Hz / 20 kHz +-0.3 dB (32 ohm loaded, 100 mW)

Line-level Output

  • Reference output level -10 dBV
  • THD: less than 0.01% at 1 kHz
  • Frequency response: 20 Hz / 20 kHz +-0.3 dB


  • Power: 5V DC (via USB port), 0.5 A
  • Dimensions: 108 mm (W) x 36 mm (H) x 140 mm (D)
  • Weight: approx. 450 g



This review was improved greatly by comments from Patrick Dillon and Tyson Neidig.

Pure Music and Audirvana Plus were donated to HifiZine by their respective developers, for the purpose of use in reviews and technical articles. Thank you for your support!



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