Wireless Music Distribution Part Three

Hi Chris,<br />

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Thanks! Actually, this is what I observed on my system as well (except for the HDCD part). But I'm curious ... leave your system exactly the same way (with Audio Midi Setup on MacBook Pro set to 24/96). But this time, select a 16/44.1 track on the Mac Pro for streaming/playback. What does your DAC indicate now? I'm guessing it still says 24/96. So therefore, we can't really tell if the Mac Pro is streaming the full res file, or (possibly) downsampling/down-converting it first. The reason I am suspicious is we know that the Mac Pro performs down-conversion if it is streaming to an AE or an Apple TV. How do we know it streams at the track's full native resolution if it is streaming to another Mac instead of the AE/Apple TV? I think the only way to really tell, as I mentioned previously, is perform some kind of more intricate data comparison. What do you think?<br />

<br />

Thanks.

Hi Osoraku - I am 100% positive it's streaming in the native resolution. I believe what you are seeing is the flaw in iTunes that won't change the sample rate until its closed and reopened. <br />

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If your DAC is reading 24/96 but you're playing a 16/44.1 file you need to close iTunes, make sure Audio Midi is set to 16/44.1 or 24/44.1, then reopen iTunes and stream that same 16/44.1 file. Your DAC will now read the correct sample rate. The reverse is true for 24/96.

Hi Chris,<br />

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Yes, I understand exactly what you are saying, and you are not wrong concerning Audio Midi setup and iTunes interaction. But I think I am not being very clear in my description. <br />

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We want to establish that high resolution content is being streamed wirelessly at its native resolution. The evidence we have so far (IMHO) does not allow us to conclude that this is necessarily the case. It might be the case, but we cannot say for sure. <br />

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Why? Because currently the only way we have of determining what the resolution of streaming content is is to look at the DAC display. But we know that the DAC display <i>always</i> says "24/96" if you have Audio Midi set to 24/96 on the remote Mac (the one feeding the DAC), <i>even if the track being sent from the server (Mac Pro) is really only 16/44.1. </i> So we can't claim that the streaming sample rate as determined by the DAC display always necessarily represents the streaming rate over the WiFi. For example, maybe a 24/96 track is being sent from the server to the remote Mac at a down-sampled 16/44.1 rate, then because the remote is set to 24/96, the stream is (re-) converted to a (now fake) 24/96 and therefore shows up at the DAC at 24/96. The DAC has no way of knowing if the stream was 24/96 all the way from the server, or if it underwent an arbitrary number of rate shifts along the way, with the last rate shift before reaching the DAC setting the stream to 24/96. And the critical point is that any downshifts in the streaming resolution anywhere along the chain, even if followed by "upshifts" before reaching the DAC, will cause loss of information, and loss of true resolution.

Hi Osoraku - Here is why I think native resolution is being streamed.<br />

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1. I am using Amarra which has auto sample rate recognition and changed Audio Midi automatically depending on the sample rate of the music being played.<br />

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2. If a 24/96 track is altered in any way the least significant bit (LSB) is also altered and the HDCD encoding is lost, thus an HDCD track will not illuminate the HDCD indicator on my DAC. <br />

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I'm willing to say 100% of the time native resolution is being streamed.

Hi Chris,<br />

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Ahh, I see. I didn't fully understand your setup. I agree the Amarra behavior and HDCD observation indicate native resolution streaming. That's excellent! Thanks very much! <br />

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With this issue answered, my plans now are to use a Mac Mini as a transport, which will pull from my Mac Pro "server". Perhaps I'll also use some local storage or external firewire hard drive. Then I'll work on improving the jittery toslink connection from the mini to my Wadia DAC. I hoping Wadia comes out soon with their rumored 27ix upgrade which will add a USB input. But I've also heard that it won't support 88.2 or 192 kHz, only up to 24 bit, at 44.1, 48, or 96 kHz. Shame since I already have a fair amount of 24/88.2 and 24/192 material. Perhaps I'll have to seriously consider replacing the Wadia (<gasp!>) with a newer piece. <br />

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Thanks again for this terrific site and your help with my question!

Hi, Chris. I've been browsing the site for some time now, find it provides a very nice resource, and decided to register. So let me start off with a dumb question. :-)<br />

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I've got the basic computer-in-the-office (old machine running Win 7) with a wireless router, AE-to-the-stereo setup, controlling AirTunes with my iPod Touch. As with many of your readers, I've wondered if there is some relatively inexpensive setup that would allow me to stream 24/96 or better to my audio system.<br />

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It was great to read that a MacBook Pro will do this, since I have plans to buy one soon. However, I'm not thrilled by the prospect of Das Wiregepluggen und Ungepluggen that would accompany hooking up and unhooking the MBP from the system.<br />

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So here's the stupid question: Would a plain old wireless USB network adapter (e.g., D-Link DWA160) be able to receive files streamed from the wireless router in the office and input them to a USB DAC (or, with suitable conversion, a non-USB DAC)? I actually don't have a DAC yet that will accept anything beyond 48kHz (old Theta, a fine piece of equipment but not built for higher data rates), but I like to plan for the future.<br />

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Now a couple of questions I hope aren't quite so dumb:<br />

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- I've recently been able to put a very good digital coax cable in the chain between the AE and the Theta. (From the AE optical out I've got a low-price Toslink into a very low-price optical-to-coax converter, then the digital coax cable into the Theta's input.) I didn't care about the rest of the chain when I had a cheap coax, but now I'm considering whether to upgrade the other links. I'm wondering (1) Is there a non-exorbitant Toslink cable that would improve the sound? and (2) Would replacing the current $20 optical-to-coax converter with the M-Audio CO2 help?<br />

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Thanks,<br />

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Jud

Osoraku and Chris,<br />

<br />

An note on the capabilities of the Audio Midi on Mac (Snow Leopard, if it makes a difference):<br />

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After your notes, I did some tinkering with the Mac Mini that I use as a directly-connected music server. I tried wireless serving from attached storage, but too many hesitations. All of the library on the Mini is ripped Apple Lossless, all standard CDs, no SACDs or the like yet.<br />

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The top output for Toslink is 24/96 as your notes mention, but USB is only 16/48. <br />

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So, I did some listening with the iTunes equalizer off (if I just turn up the volume a bit, everything balance out very nicely, so the equalizer is really only useful at lower volumes or for parties). The Audio Midi app makes it pretty easy, allowing switching on the fly. I really could not detect any difference between 4 of the 5 of the settings tried: <br />

USB 16/48<br />

Toslink 16/44.1<br />

Toslink 16/48<br />

Toslink 24/96<br />

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Not much of a surprise, considering that all of the material was 44.1.<br />

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However, the USB 16/44.1 was definitely different, sounding thinner and unpleasantly sharper. Strange that it was not the same as the Toslink 16/44.1.<br />

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Any comments?<br />

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And, thanks again for the great site.