[Review] Fostex HP-A8C 32 bit DAC

Fostex HP-A8C 32 Bit DAC, Pre-Amp & Headphone Amplifier

All Things to all Audiophiles?

Product name: HP-A8 32 Bit DAC
Manufacturer: Fostex International
UK Distributor: SCV Distribution
Cost: £899 UKP (Currency conversion) (YMMV)

Reviewer: Mike Cox - TNT UK
Proofreading: Mike Redman
Reviewed: September, 2014

These days there are so many digital to analogue converters available priced to fit any pocket. It is very hard to choose a DAC as they are all so similar in specification. Most DACs use one of a small number of DAC integrated circuits (ICs) and supporting devices like USB ICs. If you want a bespoke solution there are very few choices and they are extremely expensive like that from dCS.

The DAC has also been evolving and they are frequently equipped with a volume control and analogue inputs so a pre-amp and interconnect cables are no longer required. The Fostex HP-A8C is one of this new generation and also includes a headphone output.

Features

There are lots of interesting features and options to play with:-

High fidelity 32bit D/A converter (Asahi Kasei's AK4399) and all discrete analogue circuitry headphone amplifier.
Complies with USB Audio Class 2.0 up to 32bit / 192kHz (24bit on Windows).
Asynchronous mode by highly precise TCXO (Temperature Compensated Crystal Oscillator) clock.
Highly precise level adjustment by electronic volume control.
Large capacity toroidal power transformer.
Built-in SD (SDHC) card drive for DSD file (DSF format) reproduction.
Selectable between the internal clock and the external clock (except for USB and SD card).
Built-in up-sampling function of x2 and x4.
Digital filter multiple selection between "sharp roll-off" and "minimum delay" developed by Asahi Kasei to eliminate pre-echo.
Direct Out mode for bypassing the volume control circuit.
Variable headphone amplifier gain from 0dB to -12dB by 0.5dB step for perfect match with any type of headphone.
Various inputs including USB, AES/EBU, Coaxial, Optical (x2) and analogue RCA.
Dedicated slim line remote controller.
Beautiful white organic LED display.

My source was my regular MacBook Pro with Aqvox USB power supply, Chord Silver Plus USB cable and IFI Purifier. The MacBook was running JRiver as the media player, I use JRiver these days as it handles the majority of file formats. JRiver also has an excellent remote control application (JRemote) for the iPad.

I started with the HP-A8C in direct output mode, disabling the volume control then inserting the DAC into my system in place of my regular DAC. Straight out of the box the HP-A8C sounded hard and gritty, so I left it switched on for a week or more, listening occasionally to see if the sound changed. Over the week the sound opened out and relaxed, it improved further over the following week and now several weeks later it seems to have settled down.

With the DAC "burnt in" I experimented with other settings such as the filter type where there are two options. Sharp roll off minimises the digital out of band noise passed to the following amplifier whilst minimum delay minimises the phase impact of the filter. Next up to play with is the level of upsampling, with options for none (1X), 2X and 4X. With all these things to play with you can tie yourself up for hours playing with all the possible combinations.

Also an option available from the remote control is the selection for master clock source. The options are "Direct" or "Local" where "Direct" derives the clock from the incoming data and "Local" uses high precision oscillator on board the DAC. All the options are selectable from the remote so it is easy to sit back and play. It was easy to get very confused as to what the impact is of any of these changes. The differences are small, but noticeable, and being able to play with the settings from your regular seating position is a real bonus. All I needed were binoculars to see the display on the DAC from the other side of the room!

My approach to finding the best setting was to take them one at at time selecting the best then moving on to the next setting. Not very scientific but about the most practical approach. I ended up selecting no upsampling, local clock and minimum delay filter. While writing this review I have experimented with the setting again, and as you might expect the conclusions are slightly different. Being able to select the settings from my regular listening seat allows me to change them as my mood dictates.

Where the HP-A8C comes into it's own is when it is used as a pre-amp with headphone output as well as a DAC. It has one set of analogue inputs which is all I need for the feed from my phono stage. You now have the ability to control the volume as well as select from from multiple digital sources as well as the analogue inputs. When you now look at the price and compare with separate components and associated power and interconnect cables you have a good value setup.

Playing the music

As a stand alone DAC fed through my MFA pre-amp and Leak ST50 into the Eryk S Concept Superioro speakers and several weeks of burn in time the setup was very revealing, clearly showing up any poor recordings. As you stepped up the bit depth and data rate ladder, the sound quality improved until you reach 24 bit 192Khz. With recordings such as that from Katzenburger Music Productions the sound is now smooth yet detailed, a very enjoyable experience. The recordings from Anne-Sophie Bertrand on harp are rendered with great leading edge attack followed by the gentle decay of the resonating strings, until Anne Sophie damps the sound. The combination of the Superb recordings and HP-A8C make a good case for high definition audio.

On lower quality recordings the HP-A8C can make the music harder to enjoy, where as a less revealing DAC can still provide some good music. If we compare with my regular La Voce DAC which is based on the veteran TDA1541 DAC chip and is only capable of 24 bit 96Khz. Even at the high resolution, the La Voce does not reveal the benefits of high resolution audio. Wereas, with regular CD rips at 16 bit 44.1 kHz it gives a smoother presentation compared with the HP-A8C.

If we now use the the HP- A8C as designed, including the pre-amp, the justification significantly increases. I plugged the HP-A8C directly into the Leak ST50 and enabled the volume control. As a pre-amp with headphone output and remote control the HP-A8C really sings. For the first time in my audio history I have a remote control, not only for volume but input selection, I know, I am a dinosaur! As a pre-amp fed from my phono stage the HP-A8C works extremely well. The HP-A8C is quiet, clean sounding, adding very little of it's own personality to the presentation. You cannot ask much more from a pre-amp. I still prefer my MFA Classic pre-amp, I should as it costs much more and has no DAC!

I do not use headphones much, preferring the sound of speakers to the rather closed in and sometimes uncomfortable affects of headphones. For this review, I did try my Sennheiser HD650s and for me the HP-A8C sounded very nice. With my limited experience using headphones the sound was as good as when using my dedicated Burson headphone amplifier.

Leaving the best to last

So far I have forgotten to mention the SD card input facility. The SD card input support DSF, WAV & AIFF format music files only, and it is very picky about the file naming, only 30 alphanumeric characters. I used a 16Gb SD card and formatted FAT32 as instructed. Copying the files to the SD card is no problem but having to rename them to conform to 30 alphanumeric convention is a real irritation. If the SD card contains any files other than the prescribed DSF, WAV and AIFF formats the card is not recognised. This is all very irritating, but.... once you get it right the result is worth the effort. I downloaded some free DSF format files to test with and initially stored on my network storage device for reply via JRiver.

The results using DSF via JRiver were nice but not significantly different to the 24 bit 192kHz files I was using. Moving the files to the SD card the sound suddenly became much clearer, via USB from JRiver there was haziness that I had missed the first time around. DSF & WAV format music files via the SD card input are so good it is a pity there is not more material available. The usability of the SD card input is significantly compromised with the file & folder naming restrictions, come on Fostex give us a software update with improved file handling.

Conclusions

This DAC from Fostex is their top of the line product, and as such it is a little more expensive than the average. The build quality is superb, the functionality, as a DAC, gives you just about everything you will need. I would have liked an I2S input to allow me to try the DAC with the Pink Faun I2S Bridge, this would have been the icing on the cake. As a pre-amp, it functions well and sounds very good to me, clean clear and dynamic. The remote does the job, though I would have preferred something a little more robust than the cheap, slim plastic item. The buttons are a typical of remotes like this, soft and imprecise. The range of operation also seems limited, demanding use at arms length from my seating position.

The sound quality took a while to settle down in my system, perhaps it was my hearing getting used to the Fostex sound! Once settled in the the HP-A8C proved very flexible, the ability to tweak the sound by adjusting the filter, clock and over sampling helped to tune the sound to my needs. Using high quality, high resolution recordings, gave the Fostex the opportunity to really shine. The sound was detailed and smooth, very analogue like. With regular CD rips, the sound was extremely dependent on the recording quality. The best recordings, such as Andreas Scholl, English Folk and Lute Songs were detailed, with great recording ambience. Lesser recordings at 16 Bit 44.1Khz could sound gritty and harsh. The DSF & WAV format input via SD Card was a revelation and is highly recommended if you have the patience to live the file restrictions.

Overall I really enjoyed my time with the Fostex HP-A8C, especially with the high definition recordings. This is the first time high definition recordings have shown their worth. Older recordings remastered to high definition still sound like a waste of money. New recordings mastered in high definition are where you really hear the difference. When you consider the value proposition compared with separate DAC, pre-amp, interconnect and power cables the Fostex HP-A8C looks very good. The price was reduced while I had the HP-A8C and is now £899, with the build quality plus all the facilities and functions available this is good value.