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Sampling Rate to Choose in Audio Midi Settings in Mac.

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Posted on October 31, 2009 at 18:15:48
dgad
Audiophile

Posts: 115
Joined: July 27, 2002
 I have been trying to compare iTunes playback into a Prism Orpheus DAC using different sample rates for playback. My intention wasn't to try different sample rates, but I noticed that changing the sample rates in either the Prism Control Panel or the Audio Midi Control Panel for music recorded at different sample rates didn't lead to profound audible differences. For example a HRx recording converted to AIFF 24/176.4 played back at 44.1 didn't lead to a major sonic difference. Also, playing back 16/44.1 bit recordings at 176.4 didn't lead to a major sonic difference (although slightly better).

Am I doing something wrong. Is it OK to have the sample rate settings different than the recordings native sample rate?

I use a Mac Mini w. 4GB and have Amarra installed (trial version) but turned off. I also can't hear any difference with Amarra turned on or off. But, I do hear a difference with the Amarra trial installed or not. The playback sounds much better with the trial version of Amarra installed. This is independent of it turned on in the control interface or not. Kind of strange, but something is amiss.

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 21:44:09
cics
Audiophile

Posts: 1099
Joined: November 9, 2006
 Dgad, it's great to see you experimenting with computer transports. When done correctly, rewards are huge.

Difference between 44.1 and correctly upsampled 176.4 or 192 (better yet) is significant. If you're not religious about Mac's you should try cMP².

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 2, 2009 at 04:32:30
dgad
Audiophile

Posts: 115
Joined: July 27, 2002
 Thought about it extensively at first but I really want something very simple and I love the ability to use my iPod and Macbook (Mac Screen Sharing is such a joy - allowing me to sit on my laptop and arrange my music from my listening seat in different categories etc.) for controlling the Mac Mini setup. Also, the entire home network via Mac is too simple an interface to turn away from. I have been a strong Windows user for years but am just so tired of the viruses and updates and more that I just gave up. The Mac Mini is so simple to setup and quiet and with a baby in the house time is difficult enough to find even to burn the CD collection. I might try it in the future but my true passion is vinyl where I am all out assault. It still trumps everything and so far my EMM CDSAse is still slightly ahead in sound of my Mac Mini setup but I plan on using a SSD to see what else I can achieve. Just waiting for prices to go down a bit. I heard about Amarra a long time ago and predicated my decision on it. After extensive comparisons, I find it better but not necessarily worth the money for the $ spent. I find the difference subtle.

My main motivations were to record via the Prism hours of Dead live tapes collected over the years and also, my vinyl collection. I want to compare cartridges in different arms as auditory memory is vague at best. Also I have a ton of Children's LPs that I want to place on an iPod for music for the baby room. Hence the purchase of the Prism Orpheus. I am a big fan of Firewire DACs and the quietness of the Mac Mini head, w. a built in Firewire interface meets those needs. I hope to one day use the Mac Mini as a 2nd computer and use the Mac Mini w. an eSATA connection to my external WD drives. I wonder how long Apple can hold out.

One comparison I will do is play music off of the built in drive vs. the external drive to compare. I was about to do so last night but a tube is giving me a problem. Once sorted, I will give it a try.

Orpheus should follow MIDI, posted on November 1, 2009 at 08:53:44
JerryS
Reviewer

Posts: 1503
Joined: February 24, 2001
 Hi Darren,
I lost your email or would have let you know about the new Orpheus review.

I don't use a Mac anymore, but IIRC, when you change the sampling rate in the Mac's MIDI control panel, the Orpheus will follow automatically. The moment you select "Play", you'll hear a couple of clicks coming from the Orpheus as the sampling rate changes. You should not have to make that change in the Orpheus control panel's Global Settings.

Unless I am switching to use the Orpheus as a line-stage (locking the AO1/AO2 VOL), the only change I make in the Orpheus control panel is to change the Output Settings AO1/AO2 from Mixer to DAW. When set to Mixer, I can listen to the turntable using RIAA. When set to DAW, I listen to JRiver or Internet radio without the very slight hiss from the phono stage being part of the mix.

Happy listening.

Regards,
JerryS

RE: Orpheus should follow MIDI, posted on November 1, 2009 at 11:07:17
dgad
Audiophile

Posts: 115
Joined: July 27, 2002
 Jerry,

I have been looking for your review but didn't see it. I know you moved away from Mac but I am working on things for now. My curiousity isn't the Orpheus but what iTunes puts out. For some reason everyone says to restart iTunes and I haven't been able to hear a difference when running at 44.1 vs. 176.4 when switching on the fly. I have burned a ton of music and a lot of HRx recordings. Hopefully I will get a better feel later. Still need some better cables.

Mind you I am using the Amarra demo software. With it on or off it sounds way better. If it isn't installed it sounds terrible. Not sure why.

RE: Orpheus should follow MIDI, posted on November 1, 2009 at 16:49:26
JerryS
Reviewer

Posts: 1503
Joined: February 24, 2001
 Please see below.

It's a pain in the neck, posted on October 31, 2009 at 18:27:54
flatmap
Audiophile

Posts: 112
Location: Pacific NW
Joined: June 5, 2008
 You have to set the sample rate in Audio Midi Setup and then launch iTunes.

Want to go from Stevie Wonder at 44.1 kHz to Mahler's Sixth at 96kHz? 1.) Exit iTunes, 2.) change audio midi from 44.1 to 96 and then 3.)re launch iTunes. Repeat, in reverse, when it's time to go back to 44.1 or 88.2.

Yes, assuredly, it is a pain.

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on October 31, 2009 at 18:19:01
AudioDoctor
Audiophile

Posts: 678
Location: Minnesota
Joined: March 25, 2008
 It is my understanding, that you can not change the sampling rate in the MIDI settings without restarting iTunes.

Linked below are some guidelines on the Wavelength Audio website.

Happiness is a clean record, and warm tubes!
RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on October 31, 2009 at 22:26:16
dgad
Audiophile

Posts: 115
Joined: July 27, 2002
 I have read several times that I can't change sampling rate settings without restarting iTunes but for some reason w. my DAC it seems I can. I just change it and the DAC reboots and fairly quietly at that. I don't find myself restarting iTUnes. It stays open. I wonder if the midi settings are in fact changed this way but it sounds fine. Thanks for the link to the Wavelength website. I gather iTunes does upsampling and since I am playing back some 176.4 which is 4 times 44.1 I might as well just leave my Midi settings as such. I honestly feel it sounds a touch better. But it is subtle.

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 04:34:35
Crimson
Audiophile

Posts: 6140
Location: Jersey Shore
Joined: December 11, 2000
 You MUST relaunch iTunes for it to do any SRC. Otherwise you're getting core audio's SRC which is inferior, not to mention possible double conversion if iTunes is set to a bit and sample rate other than the native source.
--eNjoY YouRseLf!.....
RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 08:03:21
dgad
Audiophile

Posts: 115
Joined: July 27, 2002
 What do you mean by "it"? What else other than Core Audio is doing the sample rate conversion? Does iTunes have its own SRC or does it use Core Audio?

Another question is although the SR in Core Audio is changed and iTunes isn't relaunched but the DAC is restarted (this happens automatically when I change the SR in Audio Midi or the Prism Interface - both change the other automatically) does the SR change?
RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 09:12:59
flatmap
Audiophile

Posts: 112
Location: Pacific NW
Joined: June 5, 2008
 My understanding is that you are using core audio in both cases -- but iTunes sets up different parameters compared to Audio Midi. I think I learned that on the Apple forums... but I can seem to locate the discussion now. Sigh.

The DAC will look at the settings from Audio Midi, regardless of what iTunes is playing. This is easy to check visually if your DAC as an indicator for incoming sample rate.

If you start iTunes when audio midi is set to 44.1, iTunes will convert everything it plays to the target value of 44.1 kHz. Suppose your next track is 96 kHz. If, without closing and restarting iTunes, you switch audio midi to 96 kHz then iTunes will take the 96kHz source file and convert it to 44.1 kHz to match what it thinks audio midi is set for. Audio Midi will then receive 44.1 kHz input but, as it is set now to 96 kHz, it will convert the 44.1 kHz input into the 96 kHz output that it is now set for. The Dac will be happily receiving 96 kHz signal -- but which as been converted twice.

Whether these conversions make a difference in what you hear may depend on a number of factors, not least is the quality of the original source file.

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 11:03:40
dgad
Audiophile

Posts: 115
Joined: July 27, 2002
 Flatmap,

That is what I was thinking. I need to test if I can hear it. Thank you. My DAC will show the sample rate as whatever Audio Midi is set for. But,,I assume I tunes needs to be restarted after each AM change in SR. I wonder if this is true in the latest release of Snow Leopard or the new iTunes updates (one just last night).

Not to sound distrustful but can anyone confirm if this is true 100%? I will try to confirm it audibly tonight.

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 11:26:17
Bob Stern
Audiophile

Posts: 228
Location: SF Bay Area
Joined: August 28, 2001
 In a 9/12/09 post on Apple's "Core Audio API" discussion list, an Apple programmer on the iTunes team confirmed that the need to quit and relaunch iTunes when you change the sample rate is a bug in iTunes itself and has nothing to do with which version of OS X you use. He said that iTunes 9.0 did not address this bug, and that he was not permitted to disclose when they expected to get around to fixing it.

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 13:46:45
dgad
Audiophile

Posts: 115
Joined: July 27, 2002
 Bob,

Thanks. I just found an old post on AA referring to a Stereophile Article that explains it very well. Now I am clear. It is a PITA.

RE: Sampling Rate to Choose in Audio Midi Settings in Mac., posted on November 1, 2009 at 15:49:04
flatmap
Audiophile

Posts: 112
Location: Pacific NW
Joined: June 5, 2008
 Yep, it's a PITA.

It's interesting from an engineering point of view as their perspective is something like: "Why should any application running on the computer have special access to the hardware settings? All applications can access to this hardware and, what do you want, for one application to lock out all other apps?"

Of course this "no application is special" perspective is logical for a general purpose computing device. Equally natural is that those of us who use our computers as the source for music playback really do want our music player to have special rights to the hardware settings.

So I think the right kind of solution here is to have another setting in iTunes -- something like "Let me takeover Audio Midi" and other applications (like the new email message sound in your email client) would just have to be satisfied with whatever iTunes does.

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