This is a review and detailed measurements of Fostex HP-A3 DAC and headphone amplifier. Even though the product is current and listed on both Amazon and Fostex websites, I also found reviews dating back to 2011. So unless there have been some revisions, this is an "older" unit. It is on kind loan from a member and lists for USD $299 with prime shipping from Amazon.
Any memory of Fostex's long history and Japanese lineage goes out the window the moment you gaze at the ordinary and DIY-like packaging of the HP-A3:
What is the deal with the huge washer on the headphone jack showing?
Functionality is not bad with USB and Toslink inputs but is missing S/PDIF. I liked seeing the RCA/Phones switch allowing me to test the RCAs as the DAC output. Note that the volume control changes the RCA levels so you can use it to drive active speakers and such, avoiding a pre-amp.
No gain switch is included which I like to see as mandatory feature given the wild variation in headphone sensitivity and impedance.
No driver was needed as the unit only supports up to 96 kHz sampling and hence is UAC1 compliant.
Let's get into measurements and see how she does.
Measurements
As usual, I start with my Dashboard measurements using USB input:
You see what I am seeing? Two rather massive spikes at roughly 15 and 16 kHz severely degrade performance to a distortion that is at whopping 0.2%. SINAD (signal above power of noise and distortion) as a result takes a massive nosedive to very poor 54 dB.
I switched inputs to Toslink and they vanished:
While not great, at least nothing is badly broken as it is with USB.
I expect no-name companies to release such faulty products, not Fostex. Surely they have professional measurement gear to measure such obvious fault with the USB implementation.
Given how poor the performance of USB is, I am going to truncate the rest of the test and just show one power vs distortion curve using 300 ohm load:
Above was with Toslink by the way. Power is at 11 milliwatts which is OK.
Conclusions
I hate to bring bad news to members who loan me their equipment but there is no getting around the facts here. The USB implementation of Fostex HP-A3 is clearly broken. I don't know the source of that noise. It could be from within the unit, or bleeding from my computer's port in which case, the signature will be host dependent. With so many choices of DACs and amps out there, I see no reason to tolerate sub-par engineering as we see here.
This is a failing a product and I can't recommend its purchase.
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If you like this review, please consider donating funds using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
Any memory of Fostex's long history and Japanese lineage goes out the window the moment you gaze at the ordinary and DIY-like packaging of the HP-A3:
What is the deal with the huge washer on the headphone jack showing?
Functionality is not bad with USB and Toslink inputs but is missing S/PDIF. I liked seeing the RCA/Phones switch allowing me to test the RCAs as the DAC output. Note that the volume control changes the RCA levels so you can use it to drive active speakers and such, avoiding a pre-amp.
No gain switch is included which I like to see as mandatory feature given the wild variation in headphone sensitivity and impedance.
No driver was needed as the unit only supports up to 96 kHz sampling and hence is UAC1 compliant.
Let's get into measurements and see how she does.
Measurements
As usual, I start with my Dashboard measurements using USB input:
You see what I am seeing? Two rather massive spikes at roughly 15 and 16 kHz severely degrade performance to a distortion that is at whopping 0.2%. SINAD (signal above power of noise and distortion) as a result takes a massive nosedive to very poor 54 dB.
I switched inputs to Toslink and they vanished:
While not great, at least nothing is badly broken as it is with USB.
I expect no-name companies to release such faulty products, not Fostex. Surely they have professional measurement gear to measure such obvious fault with the USB implementation.
Given how poor the performance of USB is, I am going to truncate the rest of the test and just show one power vs distortion curve using 300 ohm load:
Above was with Toslink by the way. Power is at 11 milliwatts which is OK.
Conclusions
I hate to bring bad news to members who loan me their equipment but there is no getting around the facts here. The USB implementation of Fostex HP-A3 is clearly broken. I don't know the source of that noise. It could be from within the unit, or bleeding from my computer's port in which case, the signature will be host dependent. With so many choices of DACs and amps out there, I see no reason to tolerate sub-par engineering as we see here.
This is a failing a product and I can't recommend its purchase.
-----
If you like this review, please consider donating funds using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
The data is still on the graph and if there is a strong feeling, I can bring it back.
