Fostex HP-A8C 32-Bit DAC Headphone Amp
Input: Coax S/PDIF (RCA), 2 Toslink, 1 USB, 1 pair RCA, 1 SD (SDHC) Card Slot
Output: 1 pair RCA, Toslink, Coax S/PDIF
Dimensions: 213mm(W) x 78mm(H) x 314mm(D)
Availability: online and through Authorized Dealers
DSD via DoP and SDHC
Before going to press with this review, I figured I'd give it one last lap around the 'net to see if I could locate some information regarding when (or if) the Fostex HP-A8C would be able to play back DSD over PCM/USB. I stumbled on a post by 'AnakChan' on HeadFi that pointed to the Fostex Japan website and lo and behold there was firmware version 2.01B with DoP (you can get it here). Once I downloaded and updated, all I had to do was navigate to the USB over PCM menu option, enable it, and I was streaming DSD over USB in no time. Lovely. Why this firmware revision from November 2012 is not yet available on the Fostex International (English) website is anyone's guess. The latest version to be found there is 1.31 which does not include the DSD over USB option so you are stuck playing back only DSF formatted DSD files through the HP-A8C's SD (or SDHC) card reader. And that's kind of a drag.
The HP-A8C DAC is also a preamplifier and headphone amp offering a number of 24/192-capable digital inputs including Toslink, Coax S/PDIF, and a USB 2.0 compliant asynchronous USB input that includes a "highly precise TCXO (Temperature Compensated Cristal Oscillator) clock", as well as a pair of analog RCA inputs. Outputs include 1 pair of RCAs, 1 Toslink, 1 Coax, and 2 headphone jacks. Just in case you're wondering, if you use the analog inputs no signal is passed to these digital outputs so there's no A/D conversion here. You can defeat the HP-A8C's internal clock for the S/PDIF inputs via the menu and there are a host of additional options available through the menu system including upsampling for PCM data (1x, 2x, 4x), Asahi Kasei-designed Digital Filters (Sharp Rolloff or Minimum Delay), Direct Mode which bypasses the internal volume control, and System firmware update (via SD Card). You can also adjust the output gain for the headphone amp from 0dB to -20dB in 0.5dB steps to better match your 'phones input.
The HP-A8C employs the DSD-capable 32bit Asahi Kasei AK4399 DAC which is limited to single rate, 64x DSD playback. For PCM data, it will pass up 32/192 via USB (24-bit for Windows) or 24/192 via S/PDIF. Windows users will need to download and install the Fostex drivers to take advantage of sample rates above 96kHz, Mac users are ready to roll.
You can control the HP-A8C using the front controls or the included remote. As you can see from the photos, the dual headphone jacks are front mounted (where else would they be) while the SD Card reader resides around back. I found the HP-A8C to be intuitive to use and only needed to follow the simple online instructions to perform a firmware update (via SD card). Everything else was simply a matter of turning and pressing the control knob. The "white Organic LED" display shows you what to do and it also shows the selected input, volume level, and incoming sample rate during playback. I used the HP-A8C with my Leben CS-300XS in Direct Mode and in full preamp and Direct Mode with my Pass INT-30A.
The HP-A8C has a glass faceplate and is otherwise wrapped in black metal making for one difficult piece of kit to properly photograph (without finger smudges or my silly mug reflected in the glass). I find it to be nicely made and handsome to look at and potentially small enough to fit on a desktop. The small plastic remote is utilitarian and not exactly fun to use but it gets the basic job of volume control done. The remote also allows you to navigate your SD card-based files and I found its Forward/Next and Back functions to be primitive at best.
A Tale of Two DACs
While you can play DSF formatted 64x DSD files through the SD card reader, I can't imagine why you would since the HP-A8C can stream DSF and DFF files via its USB input with firmware rev. 2.01B. But to cover all the bases I did play some SD card-resident DSD files and they worked just fine. I also compared DSD playback from the SD card to streaming DSD files from my NAS and there was not an appreciable difference.
Let's get practical for a moment. A typical DSD album takes up roughly 3GB worth of storage and the max storage for an SDHC (Secure Digital High Capacity) Card is 32GB. While SDXC (Secure Digital eXtended Capacity) cards will theoretically store up to 2TB of data someday, the HP-A8C manual specifically states that their card reader is SDHC compatible, not SDXC (and remember the SD card will only read DFF files). So you can fit roughly 10 DSD albums-worth on one card. To play back SD card-based music, you have to use the front panel control knob or the remote but with my eyesight as it is, I still had to get up and get closer than my listening seat to the HP-A08 to read its display. All in all, it is certainly much less appealing than using an iPad as a remote and iTunes/Audirvana to stream DSF and DFF files from my NAS. On another practical note, you have to put your DSD files into a folder for the SD card reader to read them, and file names need to be 30 characters or less. All things considered, I preferred to play my DSD music through the HP-A08's USB input directly from my NAS. Thank you firmware 2.01B!
Once we're playing with the Fostex HP-A8C, things improve. I will say up front this could nearly have been two separate reviews; one using the HP-A8C's preamp and the other going direct out, bypassing its internal volume control. And I absolutely preferred the latter so the majority of my listening time was spent with the HP-A8C in Direct Mode using the respective volume controls of my Leben and Pass integrated amps.
But let's talk about the HP-A8C using its volume control first. Here, especially at lower volume levels, the midrange becomes noticeably forward in the mix, pushing lead singers out in front, piano keys around middle C become more prominent, and all other sounds that live in and around the midrange seem to get extra special attention. This forward-sounding presentation also tends to lessen tone colors so that there's a sameness to instrumental voices coupled with a spotlit quality to most music. While there's plenty of resolution, the overall balance is just a bit too out of balance for my tastes.
Once we go Direct, bypassing the HP-A8C's internal volume control, everything evens out. Singers are back with the band, right hands trills sparkle, left hand notes resound and all is right with the world. With the Fostex in Direct Mode I found it to be a tight sounding, dynamic, and highly resolving DAC. Tone colors are painting with a fairly broad brush although the overall sound picture is somewhat stunted, with less apparent body given to instruments and voices. While bass is fit and tuneful it is also a bit lighter weight than other DACs. On the plus side, all of this adds up to a fast and resolute presentation especially adept at unraveling complex music.
The equally endowed Mytek Stereo192-DSD DAC (see review) sounds more full-bodied all around (and I also prefer the Mytek when bypassing its internal volume) and offers up a larger and airier sound picture. The Fostex DAC is a tight-sounding player and I can see how some listeners would prefer this to a looser and more billowy sound. While we're here, the Mytek's DSD performance is markedly different from the Fostex, offering a much more dimensional sound and a startling amount of color and texture. The HP-A8C is much more reserved in comparison, where DSD playback is more akin to the qualities of HD PCM performance. Again, its overall presentation could be described as being somewhat restrained and controlled.
The headphone output of the HP-A8C shared many of the positive sonic traits of the line level output. Driving my Audio Technica ATH-W1000s, the sound was engaging and offered up a very pleasant amount of tonal complexity. I did not notice any of the shortcomings that the volume control appeared to cause through the line level outputs and would describe listening through my ear goggles (to quote Jimi Hendrix) as very much an enjoyable experience. I also stepped through the upsampling and filter options and the differences noted were subtle but I preferred 4x upsampling and Minimum Delay as I found this combo offered the fullest and smoothest sound.
I listened to all manner of music through the Fostex including various genres, different bit/sample rates from CD-quality to HD, as well as DSD from the SD Card and from my NAS, and found that the Fostex's overall strengths lent themselves very well to orchestral music. Again, in Direct Mode the HP-A8C was refined and finely detailed, providing a tight and clear image of even the most demanding music. I have heard airier presentations and generally a more relaxed sense of space while the Fostex offers a more muscular sound picture.
One Half Full
The Fostex HP-A8C certainly has its strengths and, depending on the preferences of the listener, may have some weaknesses as well (all hi-fi components have weaknesses, more and less). While I found its volume control to be less than ideal at lower levels, when run at typical listening levels or even better in Direct Mode the sound was clean, clear, tight and tuneful. While I've heard more body from other DACs like the comparably priced Mytek Stereo192-DSD DAC as well as more startling DSD performance, the HP-A8C's sonic strengths, which are best highlighted by orchestral music, coupled with its preamplifier that includes multiple digital inputs as well as an analog input, dual headphone capability, and DSD playback via USB or SD Card, all add up to one potentially compelling package.
Also on hand and in use during the Fostex HP-A8C review: Teac UD-501