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.

Thanks, Rob

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.

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)

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.

Only your ears can tell ...

--
Adrian C

"Rob" wrote in message
news
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.

This depends on the media you are playing. Media plays best in the format
it was recorded at.

If the files you play are MP3 and MP4 and the like, 44.1 / 16 is what you
want.

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.

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.


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.

Only your ears can tell ...


I doubt it! Although I have to say it does sound pretty good, at least
compared to what went before.

In article , 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.


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.

Don't know what software you have as I don't take much interest in Macs.
However I'd hope your playing software will tell you the sample rate of the
file being played.


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.

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. However
you could try asking Cambridge Audio.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

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

On 08/02/2010 19:17, Arny Krueger wrote:
wrote in message
news
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.

This depends on the media you are playing. Media plays best in the format
it was recorded at.

If the files you play are MP3 and MP4 and the like, 44.1 / 16 is what you
want.


Yep, thanks. As you might gather from another reply, it's a little
difficult following which software does what.

Rob

"Rob" wrote


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


Hi Rob - my Mac Mini died suddenly after only two weeks!

Gone and refunded* now, I don't think I'll go that route again - there are
some very pleasant aspect to the Mac system, but from what little I saw and
remember of it, 'iTunes' was the least appealing thing on it! I know you
could resist without too much of a struggle, but it seemed to want to take
me 'shopping' every time I looked at it!


*After a phone call from me to collect the £21.07 they knocked off the
refund for no reason other than it was (is?) obviously worth trying it on!

Rob wrote:

On 08/02/2010 19:17, Arny Krueger wrote:
wrote in message
news
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.

This depends on the media you are playing. Media plays best in the
format it was recorded at.

If the files you play are MP3 and MP4 and the like, 44.1 / 16 is what
you want.


Yep, thanks. As you might gather from another reply, it's a little
difficult following which software does what.

It is a tricky subject.

What would be best is "bit perfect', what comes out is what went in
unchanged in any way, this is something more than something simply coming
out at the same sampling rate.

Foobar2000, with a plugin, did just that here on Vista, foobar2000 takes
sole control of the output card bypassing the digital mixer which is the bit
that "messes" things up. (Being Vista it could not play MP3s without
glitches so despite being bit perfect it was in fact useless.) The rationale
from Microsoft was along the lines that their software manipulation of the
data was so very clever that bit rate conversion was just fine.

I now use a Mac mini, which may be no more inherently 'bit perfect' than
Windows, there is still a mixer in there to add in computer bleeps etc.,
obviously those are all turned off but the mixer will still be there but
with one input mute.

To duck the bitrate issue I use the analogue output from the Mac mini which
sounds very good to me. The thought does occur that the sound is going
through that digital mixer anyway so what I am listening to is not 'bit
perfect' after all.

I did say it is tricky.

Anyway while googling and failing to find any actual facts, just look at
this :-

http://www.computeraudiophile.com/co...ct-digital-out

"It is well known that any lossless use will not sound as good as a flat PCM
file like AIFF or WAV." and "Just in the same way that FLAC does not sound
as good as WAV on a PC.", by one J Gordon Rankin.

Surely that is just crap, at least I hope it is.

--
David Pitt

In article , Rob
wrote:
On 09/02/2010 09:29, Jim Lesurf wrote:
In a.com, Rob



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.

IIUC the above shows that the Mac hardware is quite capable of providing
both 44.1 and 48. If so, your main 'challenge' (as managers say) is to find
software that simply passes out the data at the correct rates in every
case. Afraid I can't say anything about that with the Mac as I know little
about Mac software.

If I get a chance I'll ask a colleague who is a Mac user to see if he
knows. However my impression is that many computer users have zero
awareness of this issue and blindly assume that if they can hear sound it
must be "working OK". They then blame any nasty noises on the source
material.


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#

Not yet looked at the above link. However I do get Stereophile on
subscription and remember reading the DACmagic review (and a later addition
to it IIRC). My impression is that operation with the USB will depend on
how evenly the computer sends the data. If so the real problem is initially
down to that.

FWIW When I started using my DACMagic i fed it from the computer via USB
and then ran an optical output from the DACMagic to my Meridian 563 DAC for
the actual conversion. In effect just using the DACMagic as a USB-SPDIF
convertor, and then having the Meridian reclocking the data to suppress any
jitter.

However I also experimented with using the DACMagic without the Meridian
and eventually decided that also sounded fine. Decided it sounded
indistinguishable to me. So I now just use the DACMagic and am moving the
Meridian on to other duties. Another advantage of this is that the DACMagic
can playback digital recordings at rates above 48k from my new HD P2.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html