Here is a set of 96/24 format FLAC files recorded from various DAC and amplifier outputs that you can compare against each other and a reference file (A.flac).
The list of files - warning: more than 500 MB total download size:
sample.flac - the original sample (created from several short samples taken from various other blind tests, the total length is 3:32, so it is fairly long); Note: for ABX testing, use A.flac as the reference instead, since sample.flac is not level matched with the other files, and it has a different sample rate (therefore making your DAC more of a factor in the test)
The following FLACs are all in 96/24 format, level matched and synchronized for ABX comparisons:
D.flac - from rec_alc269.wav
E.flac - from rec_d1.wav
F.flac - from rec_alc887.wav
G.flac - from rec_amp_stx.wav
H.flac - from rec_alc269_dt770.wav
Detailed description of what each recorded file is:
rec_alc269_dt770.wav - RealTek ALC269 onboard audio codec in a laptop, driving a DT770 Pro 250 Ω at full volume (0 dBFS = ~1 Vrms unloaded = slightly more than 100 dB SPL). The output impedance is about 18 Ω. Many/most people on these forums would expect this setup to be "loud enough but not driven properly" (of course, what is loud enough for one person, might not be loud enough for another). Can you hear it ?
rec_alc269.wav - the same laptop onboard headphone output driving a pair of 22 Ω resistors instead. Impressively, it still has less than 0.01% THD with an almost full scale 2.5-3 kHz tone.
rec_alc887.wav - ALC887 onboard line output of a desktop PC at full volume (0 dBFS = ~1.25 Vrms unloaded, output impedance is >200 Ω + 10 uF capacitors; 5.4 kΩ load)
rec_amp_d1.wav, rec_amp_stx.wav - an LM3876 based speaker amplifier driving 8 Ω resistors at 0 dBFS = slightly less than 11 Vrms (about 15 W, more than 100 dB SPL with efficient speakers) + pre-amplifier with volume, balance, and tone controls (4xNE5532 op amps). This is included mainly to test how the sound is affected by a long and complex "chain", with a total of up to 10 amplifier stages, at least 4 coupling capacitors, and 4 potentiometers in the signal path, in addition to the DAC and ADC chips. The balance and tone controls were set accurately for the flattest response and minimum channel imbalance (which is eliminated by the software level matching anyway). Those who believe in "op amp rolling" may also be interested to hear if so many cheap op amps really noticeably degrade the sound quality
rec_d1.wav - Xonar D1 line output at full volume (0 dBFS = ~1.935 Vrms unloaded, output impedance is 100 Ω + 220 uF capacitors; 5.4 kΩ load)
rec_stx_dt770.wav - Xonar Essence STX headphone output driving a DT770 Pro 250 Ω at -13 dB volume relative to the 7 Vrms full scale output (0 dBFS = ~1.5 Vrms loaded = ~105 dB SPL, 10.3 Ω output impedance). This headphone amplifier gets a lot of criticism on the other sub-forums, and there are also frequent claims that high impedance headphones are "loud enough but not driven properly" by it
Edited by stv014 - 2/4/13 at 2:40am