Educate me please

Posted by: sheffieldgraham on 19 February 2011

I'm currently listening to Radio Paradise, as recommended by Paul Stephenson, through my system using i-Tunes/MacBook Pro/M2Tech HiFace/nDAC.
The broadcasting bit rate is 128kbps.
Here's the question: When I set the Format to 64kHz or 128kHz on the MIDI setup the sound is like a record being played at half speed. When I set it to any other Format sound is normal. Why?
In addition anything at or above 96kHz brings the HD LED of the nDAC on. I know that if the nDAC receives a signal under these circumstances this is the case, but is it true HD?
What would be the optimum Format setting on the MIDI under these circumstances?

Regards Graham

Posted on: 19 February 2011 by DT79

Hi Graham,

The bit rate isn't the same as the sample frequency, which is what you're altering in Midi. I't not possible to say with certainty what the sample rate of the music being received is, but in all likelihood it's 44.1khz or 48khz. I'd quit itunes, change the midi setting to 44.1 and restart itunes.

It's not true HD in answer to your second question. The DAC will acknowledge an incoming 96khz signal, however this has been upsampled by the Mac, so it's not 'true HD' - same as a standard definition TV broadcast being upscaled by your HD tv so that it fills the whole screen, rather than just a small square in the middle of it.

Posted on: 19 February 2011 by sheffieldgraham

Thanks DT79,

Out of curiosity I'd be interested to know why the broadcast appears to be playing in slow time when 64kHz and 128kHz are selected on the MIDI.

Posted on: 19 February 2011 by DT79

Agree - I'm not quite sure what can be going on there!