ASIO on PC & Mac with iTunes & Apple Lossless

Thanks all. After reading online that the combination of the Apple Losses, iTunes and Airport Express with the Monster Toslink was a bit perfect combination, I decided to go spring for the couple of hundred dollars to test out the theory. By the way - I'm using an old iMac as the computer now (Mac -- Digital Signal Mover (U24, Airport Express) -- Benchmark Media DAC-1, Threshold T200 Class-A, B&W 803s).

Finally, the stage opened up! I can do a relatively quick A/B/C comparison now:

A) U24 Waveterminal going through digital coax to my Benchmark DAC-1
B) Apple Airport Express going through digital optical to my Benchmark DAC-1
C) My CD player going through digital optical to my Benchmark DAC-1.

I have the equalizer turned off in iTunes, along with any Sound Enhancement and Sound Checking.

Without some kind of ASIO driver that can use Apple Lossless Codec - there is still a huge difference between Option A and Option C. It's not as bad on the Mac as it was on the PC, but it is clearly there. The big impact is on the shape and size of the soundstage. The stage is flattened out and squashed wih Option A. The actual sound quality appears good - so if you're not sitting in the sweet spot, it's not that noticable. If you are, it's pretty clear. For some reason, Option A also seems to attenuate the bass part of the music a bit.

Comparing the Airport Express (Option B) against the CD (Option C) yielded much better results. The stage opened up huge and wide and deep. The quality of the sound was indistinguishable to my ear between these options. I have a few songs that I like to use to test stage size (e.g. Crazy by Barenaked Ladies from their album Gordon). It's not my favorite song, but they were monkeying around with the stage size and it expands well beyond the speakers. The Airport Express Option clearly was nailing this song.

Finally, a good sign that we're not doing a lot of processing on the Mac - the volume control is greyed out. I optimistically named the AIrport Express Base Station 'Bit Perfect'. I think it may have earned its title.

I will try out Foobar / ASIO / Apple Lossless when it comes out on Beta - I can do that easily with the U24 -- PC on A and the Airport Express -- Mac on B. I'll keep an eye on that and report back to everyone when it comes out.

Daryll.

http://www.dbpoweramp.com/
http://www.dbpoweramp.com/dbpoweramp.htm
http://www.dbpoweramp.com/codec-central.htm

Has anyone played with PowerAmp & their new Apple Lossless decoder? I'm wondering whether it will work with an external MAudio ASIO capable sound card.

Daryll.

Update from a friend of mine...

XP has four methods for outputting audio via an audio device. DirectSound, WaveOut, ASIO, and kernel streaming.

DirectSound and WaveOut go through kmixer. ASIO and kernel streaming don't.

Depending on which output you pick, you get what you get.

Going through kmixer = not bit perfect.

iTunes/XP is a pure DirectSound/WaveOut application. It uses QuickTime as it's I/O processor, and all the filters and codecs are buried in QuickTime. They don't register as codecs in XP. This is important in that the Apple Lossless Codec can't be used by other programs.

The only QuickTime options I can get to show up are DirectSound and Wave Out. I cannot patch in an ASIO plug-in.

Even if I use S/PDIF out, there is still a Windows volume control present, which means kmixer is active. Even if you don't have Windows XP volume control panel active, kmixer still may be active.

The only real test I've found to determine if kmixer is active is to play a DTS/DD encoded bitstream to my Fosgate /Audionics FAPT-1 Pre/Pro and see if it will decode it properly. If Bit perfect, it will decode. I cannot get iTunes to do this using any soundcard I have, including the M-Audio Delta 410, an 8 channel 24bit 96 kHz card.

Even if there is no kmixer, the soundcard you choose MAY RESAMPLE. Means that you could put in a 44.1 kbps .wav stream, only to have the soundcard upsample to 48kHz and then downsample back to 44.1 kHz ARGHHH!!! Many of the Creative Labs SoundBlaster cards do this because all their processing algorithms only work in a 48 kHz 16 bit space. All of the AC3 soundcards do this, and most output stereo audio as a 48 kHz bitstream.


Now the conjecture:

Proprietary applications may bypass kmixer. Some RME cards may do this, perhaps by using the kernel streaming function in XP. Sounds plausible, but.....no one has confirmed it will work with iTunes. Need to verify.

USB audio devices are just like any other audio device to XP, and have the same options (directsound, waveout, asio, kernel streaming). With iTunes and XP, since ASIO and kernel streaming are NOT options, then, even with USB, you are not bit perfect.


Conclusion:

There is no proven bit perfect solution for iTunes on a PC based platform.

This leaves the following options:

1.) Convert Apple Lossless files back to .wav files, and check for bit-perfect output via direct file comparison.
2.) Buy a MAC.
3.) Hope that future versions of QT will allow an ASIO plug-in. (Unlikely due to the Apple plug-n-play philosophy.)
4.) Hope that someone will supply an ALC equivalent as a stand alone codec.