I bought the Hub hoping to play some hi-def audio (24/96) over the optical output to an external DAC. I was really dissapointed when my external DAC indicated that the files were being down-converted to 48k.
More important to me was whether it was still outputing the 24 bit depth. I couldn’t get any response clarifying this one way or the other, but I did notice that the 24/96 files did sound very good even when down-converted to 48k.
Tonight I tried to come up with a way of determining if the 24 bit depth was retained. What I decided to do was create a test file at 24/96 containing a test tone recorded at -110dB. If the audio were being truncated to 16 bits which has a noise floor of 96dB then the test tone would be lost in the noise.
My recording setup has a noise floor of about -80dB (noisy preamp) so in order to make the file, I recorded a 1kHz test tone at -60dB… 20dB above the noise floor and then used the amplify effect from Audacity to amplify the signal by -50dB.
This produced a test file with the test tone at app. -110dB and the appearant noise floor at -130dB.
I loaded the test file on to the Hub and took the fibre output to the SPIDF optical input on my Mac. I recorded the output of the Hub using Audacity again at 24/48 (since the Mac indicated that the audio was being down-converted to 48k).
When I looked at the recorded file, there was my 1kHz test tone sitting at -110dB and the noise floor showing at -130.
I think this clearly indicates that the Hub will put out 24/48 which is great news since I am more interested in getting the best dynamic range and lowest quantization errors from my music.
