[Deiz]

So, being a Linux user I have no idea how OS X's audio subsystem functions.

In time my friend will likely have a USB DAC/Amp attached to his laptop, on a permanent basis. If it's kept plugged in, will audio output be routed to it instead of the onboard output (Including the Mini-to-Toslink via anal probe adaptor.)?

It'd be ideal to have audio output routed to the DAC and onboard audio simultaneously - Thus when the portable DAC/Amp is turned off, it can stay plugged in and charged, while his desktop setup will receive input via Toslink.

 

[Currawong]

When you plug a mini-optical cable into the headphone port, the system auto-switches to optical output on that port.

You only need to concern yourself with two things in Mac OS X: The Sound settings in System Preferences (for switching input and output), and "Audio Midi Set-up" in /Applications/Utilities. The latter allows you to set the output bit-rate. If you set it to, say, 24/96, then 16/44.1 audio will be up-sampled, but very well. Whether you want this to happen or not is a matter of personal preference. I have 24/96 files from Linn Records, so I leave output at 24/96.

If you want to play around with Core Audio, as it's called, there is means to do so, but it's usually only something you consider if you wan t to run an audio plug-in.

 

[krmathis]

What 'Currawong' say.
Your friend may want to look into using the SoundSource application though. Quote:

SoundSource is a tiny tool for OS X enabling you to switch your audio input and output sources with a single click, and even adjust their volume settings.

 

[whaleyboy]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif If you set it to, say, 24/96, then 16/44.1 audio will be up-sampled, but very well. Whether you want this to happen or not is a matter of personal preference. I have 24/96 files from Linn Records, so I leave output at 24/96.

Hmmmm - I am running TOSlink out of my Mac into an upsampling DAC. Is it better to have the computer do the upsampling to 24/96 and let the DAC work it's magic after the computer massages the stream or is it better to have the output set to 24/44 (or 24/48 or whatever).

FWIW, I had it set to 24/44 and just changed it to 24/96. I am listening to some rock (DCFC) at a low level and can't tell any difference at the moment.

Most or all of my stuff is RIPed to ALAC.

I guess that I am just trying to understand what you meant by the stream being upsampled "very well" above. Is there some trade off that I should be aware of?

If the answer is try it and see then that's cool - a fun weekend project.

 

[krmathis]

^ /me vote for a try, hear, and report back project.
Cause it all depends on the upsamling implementation in the DAC (differ between DAC's) vs. the Core Audio one.

 

[Planar_head]

Upsampling is a bit of a black art, some say it destroys the music, some say it sounds better, but ultimately it comes down to how the DAC handles the upsampled signal and how it was upsampled.

 

[royewest]

Brad Johnson, who works for Lavry, has a helpful post on some subtleties of using the Mac as a digital source here (you may need to register on the Lavry forum to read this):

Lavry Engineering blah blah

Benchmark also has a helpful documents on this topic, for example here:

OS X Audio Playback - Setup Guide - Benchmark

 

[whaleyboy]

Thanks for the links.

I had already set my word length to 24 bits. I am trying to figure out what happens when I ask OSX to upsample to 96kHz instead of 44.1.

I have been messing with it a little this morning and, in my setup, it *seems* that the sound is a little warmer at 24/44.1 vs 24/96.

My DAC, the CA840c, does all kinds of upsampling magic in hardware and I imagine that they are (slightly?) better at it than doing some upsampling on my Mac prior to sending the stream over.

The Apple dev notes don't have much information about what they do to the stream when it is "upsampled" - at least not the ones that I could dig up so far. I wish that I had a pal in the Core Audio dev group.

 

[Currawong]

Quote:

Originally Posted by royewest /img/forum/go_quote.gif Brad Johnson, who works for Lavry, has a helpful post on some subtleties of using the Mac as a digital source here (you may need to register on the Lavry forum to read this): Lavry Engineering blah blah Benchmark also has a helpful documents on this topic, for example here: OS X Audio Playback - Setup Guide - Benchmark

Thanks for those links. I've seen the Benchmark one, but not the Lavry one. I was contemplating getting something like the Trends box that allows AES/EBU, optical and coax output from USB to experiment.

I've just had a go at switching around the sample rate in Mac OS X between 44.1 and 96, restarting iTunes every time. I've also switch off and on up-sampling on the Northstar. I don't know if it's an illusion, but something sounds very slightly different about the sound with up-sampling in Core Audio, as well as the Northstar. Maybe it's an ever so slightly softening of the sound, which means, correspondingly that no up-sampling sounds very slightly more harsh. The difference, if I'm actually hearing anything at all, is so slight that I'd have to be using a STAX rig and be fanatical to even care.

 

[royewest]

I wish I had the gear to measure this stuff.

 

[whaleyboy]

Quote:

Originally Posted by royewest /img/forum/go_quote.gif I wish I had the gear to measure this stuff.

You do! Your ears

.

In my setup I am getting a slightly different result than the poster above. Setting my "stream" to 24/44.1 gives the best result - I err, misspoke, above when I used the word warmer to describe the 24/96 stream. It is slightly less dynamic when I use my Mac to upconvert the stream.

I tried switching it around on a bunch of different types of music and I have come to the (tentative) conclusion that I prefer 24/44.1. I can only assume that my DAC is better at the upconversion black magic than my operating system.

 

[krmathis]

Quote:

Originally Posted by royewest /img/forum/go_quote.gif I wish I had the gear to measure this stuff.

Well, you do!

Exactly what they they are for...

 

[[L]es]

wings ?

 

[krmathis]

Quote:

Originally Posted by [L]es /img/forum/go_quote.gif wings ?

Hmmm...