Jeraldo
Joined: 10/09/05
Posts: 2132
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Sample Rates->Analogue outputs for Mbks and iMacs
#986439 - 08/05/12 11:01 PM
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When playing files at higher sample rates, say 88.2 and 96K, is that what is coming out of
the analogue output? Or is there some internal SRC (reduction) going on for the analogue
outs? Is the D/A converter up to the higher sample rates?
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chris...
active member
Joined: 12/03/03
Posts: 4152
Loc: Glasgow
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Re: Sample Rates->Analogue outputs for Mbks and iMacs
[Re: Jeraldo]
#986443 - 08/05/12 11:35 PM
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Hi,
The audio interface runs at whatever speed is set in Audio/Midi
setup.
If you play a file with a different sample rate, the audio will be
converted as necessary.
That applies to ANY audio interface - and in the case
of the built-in analog output, it's more than sufficiently crap that you don't need to
worry about such subtleties.
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Jeraldo
Joined: 10/09/05
Posts: 2132
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Re: Sample Rates->Analogue outputs for Mbks and iMacs
[Re: chris...]
#986452 - 09/05/12 01:12 AM
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Thanks, Chris.
Perhaps this explains the unusual phenomena I've experienced with
certain apps having their own SRC's, often also listed in the "output" section of the
software (as opposed to SRC preferences) which can all sound a bit different, ostensibly
while no SRC is taking place. But perhaps it is, because of what you've just described.
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chris...
active member
Joined: 12/03/03
Posts: 4152
Loc: Glasgow
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Re: Sample Rates->Analogue outputs for Mbks and iMacs
[Re: Jeraldo]
#986508 - 09/05/12 10:48 AM
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Quote Jeraldo:
Thanks, Chris.
Perhaps this explains the unusual phenomena I've experienced with certain apps having
their own SRC's, often also listed in the "output" section of the software (as opposed to
SRC preferences) which can all sound a bit different, ostensibly while no SRC is taking
place. But perhaps it is, because of what you've just described.
Yep - I think you're right. Apps may perform SRC
at times, independently of (or in addition to) the OS.
One example is
iTunes, which I believe fixates on whatever sample rate the interface is set to *at the
time iTunes is launched*. This leads to the following rather less-than-optimal
situation:
You start iTunes and happily listen to some 44.1kHz material.
Then you decide to listen to a track recorded at 96kHz. So you go to auto/midi setup and
switch your high quality sound card to 96, and then hit "play" in iTunes. That may seem
correct, but what actually happens is iTunes is still operating at 44.1, so it will
convert the data to 44.1, before handing it to the OS. Then, the OS will see the
soundcard is operating at 96, so will convert the data back to 96, before sending it to
the hardware. So you have two conversions, when you thought you had none 
Of course, this is done in the name of user-friendly operation. Anything can be played
by any app at any time. Nothing can accidentally get played at the wrong speed (pitch)
etc.
In the above example, a solution is to quit-and-relaunch iTunes AFTER
changing the sample-rate in audio/midi setup. At least, if you remember! Sadly there's
no indication whether stuff is set right or not (ie. what sample-rate iTunes is
using).
There are alternate player apps which do not do any SRC, and claim to
be 100% bit-transparent. I sometimes use Audirvana. But none of this is likely to be relevant if using the
crappy built-in audio 
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