Asus HDP-R1
As I have quite a CD collection, I decided to ease up my task of climbing up the CD rack ladder each time I want to hear the "A" CDs. So I decided to make a copy of all my collection to hard disk. MP3 was out of the question, it chokes the recording acoustics, but recently a new unit using the RTD1073 Realtek processor and supporting lossless formats entered the market, the Asus HDP-R1. FLAC was supported, so I bought the unit.
The question was: Has the unit the necessary quality for high-quality listening? Well, I decided to test it in comparison with 2 other CD/DVD based media players, a Sony DVP-S715 and a white brand Mitsai MDP009 that I use mainly for background MP3 on my 100V system running around the house or to play some region-locked videos I bought abroad.
So a (very ugly and entirely improvised) test setup was prepared, using a CBS Records - CD-1 Standard Test Disc, also converted to FLAC and fed to the HDP-R1, and the three dvices under test were measured by an Audio Precision Portable One Plus test instrument. Here are the results:
I can say that the HDP-R1 is not too bad apart the omni-presence of an ultrasonic tone at 280kHz at about -31.5dbFS that is bound to degrade noise specifications and induce aliased IMD. I even disconnected the video output to see if I was missing some capacitive, inductive ou ground coupling outside the device. No, it was still there. That is probably the result of a hardware design flaw and should definetely be corrected (not by filtering at the output, at the source. Some internal clock is most certainly leaking into the D/A converter. I have described this effect in one of my past papers. The excess THD and the extreme linearity deviation at -100dBFS with dither may have to do with it, note that at -90dBFS the unit still performs quite accurately. Note that it is possible for a unit to use high-precision converters and have the performance of a lower-grade converter by improper design.
There is a cut at the extreme low frequency that, in spite I don't understand (that may be easily corrected), does not bother me too much, the unit is 0.8dB down at 17Hz, and does not compare with the other units, much more flat at low frequencies. At 20KHz, I measured about -0.4dB, which is typical of a medium-grade player.
To conclude, the HDP-R1 is not a top quality player, but could be turned into one. At the moment it is halfway between the two other players measured, and can still be substantially improved. The old Sony is still a good player, and the Mitsai, well, is a good value for the money...The HDP-R1 is usable for my purposes, but I will try to modify it in the future so as to lower that spurious tone on the analog outputs. For the moment being, I am not worried, I am using the optical interface.
On the subjective side, and using the optical interface, the unit does its job as a transport system. Switching from optical to analog, well, there is a subtle difference, but not precluding normal use...