On 09/02/2010 09:29, Jim Lesurf wrote:
In a.com, Rob
wrote:
On 08/02/2010 19:04, Adrian C wrote:
On 08/02/2010 16:50, Rob wrote:
I've connected a Cambridge Dacmagic to a Mac Mini via the optical
connection, and I'm not sure which settings to select in the Apple
audio setup, for stereo playback through iTunes. It offers a variety
of 2ch settings with a variety of formats (44.1 - 96) and bits (16 -
24). They all work, but I'd like the theoretical best setting, if
there is one.

The 'theoretical best' would be for the rate to always match that of the
source material. Not to have one rate regardless of source.


OK, thanks. I was thrown by the fact that the DAC seems to take a signal
and upsample, regardless.


Whatever suits the bit rate and depth that is common between the
majority of media files played back. 16bit / 44.1kHz for things
sourced from CD (even as an iTunes download)


I've not knowingly recorded anything at anything else. That's not to say
there's nothing else there of course.

An advantage of the DACMagic is that it has a set of LEDs that show you
what sampling rate it is receiving. So the basic check is to play files
whose sample rate you know and look to make sure the correct LED comes on.
So if you play a CD Audio file or the BBC iPlayer the '44k' LED should be
lit, but if playing an LPCM DVD Video then the '48k' (or higher if lucky)
one should light.


Indeed it does.

Don't know what software you have as I don't take much interest in Macs.

No, that's fine, and FYI it's called 'iTunes'.


However I'd hope your playing software will tell you the sample rate of the
file being played.


It does, yes.


Though what happens if you replay audio snatched from a DVD? If you
are met with silence, you may have to occasionally reset output to
48kHz, and remember to set it back afterwards - or just leave it at
48kHz and hope that the internal circuits do a decent job of 44.1/48
resampling.


Yes, (but) I think iTunes sorts all that sort of thing out.

The DACMagic LEDs will tell you if the rate being output matches the source
material or not.


And . . . it depends. iTunes tends to sample up/down to 44.1,
regardless. I say 'tend' - if I use another application, Plex, for music
replay it changes system settings to 48/16 as if by magic - just FYI as
an example of the carnival going on behind the scenes. I can't find any
Mac software that will output the file in the recorded format.

The output depends on the system settings, which will not respond to the
audio file's format, and the applications software (iTunes, etc).

What that *can't* tell you is if the output is 'bit perfect' or not. To do
that you need to record the output sample stream and compare it with the
source.


Again, since I don't know much about the Macs I can't say.

Yes, I see.

However
you could try asking Cambridge Audio.


There's a fair bit on t'internet, and it seems to make a pretty good job
of things using the correct settings, but apparently the USB interface
isn't up to much - sounded fine to me, have to say.

http://www.stereophile.com/digitalpr...r/index2.html#

Rob