PDA

View Full Version : TC-7520 and 24bit/88.2kHz



Krisbee
07-06-2010, 16:12
I had always thought that Stan's TC-7520 was restricted to 16/20/24 bit and 44.1/48/96KHz, but unless my ears and eyes are deceiving me the optical inputs handle 24bit/88.2kHz as well.

As both the receiver chip (CS8414) and DAC chip (PCM1796E) specs mention 88.2kHz, I suppose I should have realised it would.

Yet it's not a fact that is mentioned anywhere on Stan's website, only in his TC-7520 instruction PDF ( for inputs 1,2, and 3, quote : “all sample rates between 28 and 96kHz are supported”). Nor is it something many, if any, reviewers highlight ( e.g. http://www.guru3d.com/article/beresford-tc7520-dac-amplifier-review/ )

As interest in, and the availability of, high resolution audio files is increasing I wonder if Stan is missing a valuable marketing point here. Linn Records, for example, has quite a lot of material available in 24bit/88.2kHz format.

I tested this on a PC running Sidux 64 bit with ALSA 1.0.22 and kernel 2.6.34. Optical out is from a Chaintech AV 710 PCI audio card clone made by hitpoint and which is based on the Eny24HT-S audio chip as used in more expensive audio cards. The Linux sound module snd-ice1724 was loaded with “option model=prodigy71”. This gives access to all the rates the Envy24HT-S chip supports, including 88.2kHz, 96kHz, 176.4kHz and 192kHz. With this configuration, Linux effectively treats a cheap audio card like a more expensive Audiotrak Prodigy 7.1 card.

Test File used was “ForUntoUsSurround88.flac” from http://www.linnrecords.com/linn-downloads-testfiles.aspx, and after conversion with sox, “ForUntoUsSurround88.wav”.

Results:


$ mplayer -ao alsa:device=plughw=0.1 ForUntoUsSurround88.flac
MPlayer UNKNOWN-4.4.1 (C) 2000-2010 MPlayer Team
Can't open joystick device /dev/input/js0: No such file or directory
Can't init input joystick
mplayer: could not connect to socket
mplayer: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing ForUntoUsSurround88.flac.
Audio only file format detected.
================================================== ========================
Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
AUDIO: 88200 Hz, 6 ch, s32le, 5838.7 kbit/34.48% (ratio: 729839->2116800)
Selected audio codec: [ffflac] afm: ffmpeg (FFmpeg FLAC audio)
================================================== ========================
AO: [alsa] 88200Hz 6ch s32le (4 bytes per sample)
Video: no video
Starting playback...
A: 26.7 (26.7) of 30.0 (30.0) 6.7%

MPlayer interrupted by signal 2 in module: play_audio
A: 26.7 (26.7) of 30.0 (30.0) 6.7%
Exiting... (Quit)



aplay -v -D plughw:0,1 ForUntoUsSurround88.wav
Playing WAVE 'ForUntoUsSurround88.wav' : Signed 32 bit Little Endian, Rate 88200 Hz, Channels 6
Plug PCM: Route conversion PCM (sformat=S32_LE)
Transformation table:
0 <- 0
1 <- 1
Its setup is:
stream : PLAYBACK
access : RW_INTERLEAVED
format : S32_LE
subformat : STD
channels : 6
rate : 88200
exact rate : 88200 (88200/1)
msbits : 32
buffer_size : 32768
period_size : 8192
period_time : 92879
tstamp_mode : NONE
period_step : 1
avail_min : 8192
period_event : 0
start_threshold : 32768
stop_threshold : 32768
silence_threshold: 0
silence_size : 0
boundary : 1073741824
Slave: Hardware PCM card 0 'Audiotrak Prodigy 7.1' device 1 subdevice 0
Its setup is:
stream : PLAYBACK
access : MMAP_INTERLEAVED
format : S32_LE
subformat : STD
channels : 2
rate : 88200
exact rate : 88200 (88200/1)
msbits : 24
buffer_size : 32768
period_size : 8192
period_time : 92879
tstamp_mode : NONE
period_step : 1
avail_min : 8192
period_event : 0
start_threshold : 32768
stop_threshold : 32768
silence_threshold: 0
silence_size : 0
boundary : 1073741824
appl_ptr : 0
hw_ptr : 0
^CAborted by signal Interrupt...

The audio card's optical output has to referenced as "plughw" and not "hw", as Envy24 chips required bit depth padding to S32_LE format..

Peter Galbavy
08-06-2010, 09:38
The only 88.2 music I have is from Seal's DVD-Audio. It works from the Touch fine. I suspect however that 99% of any 88.2 content you find will really just be upsampled 44.1 content.