Bottlehead Forum
Bottlehead Finished Products => Legacy Products => Bottlehead DAC => Topic started by: aroide on March 24, 2015, 02:38:29 PM
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I just received my DAC and I have an issue. I've already worked through the startup sequence and sample rate glitch protocols, and I do not have issues there.
I'm driving from USB and my DAC sounds clipped and nasty. I can get sounds for a few seconds, then the DAC is dumped from my mac mini (latest version) as a device. This happens consistently and also happens from my apple laptop running different software. Same issue every time.
More info: sample rate displays correctly always and I've tried 44.1 files. I might have tried others but I can't recall. DAC power is clean as a whistle driven from a PS audio regenerator. DAC is driving a BeePre. My old DAC worked fantastic in this exact same setup. I tried both audirvana and mac mini audio output... same major sound quality issue. I don't have a reliable SPDIF or coax source to try. But I'll try and figure something out there.
Did I get a bad DAC?
Tony
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This is not a situation that we have heard of before, so it might be worth checking out the other inputs to see if we can narrow down the possibilities. Can you try running TOSLINK out from the Mac Mini?
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OK updated my thread saying toslink didn't work. I had the switch backwards...
toslink 44.1 does work and sounds fine. USB is not usable on several macs with different usb cables and sources (audirvana 2.0, 1.5, and system output). All USB is clipped, distorted, and not listenable.
I have other xmos 2.0 USB dacs on these same systems that work just fine.
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So you hear badly distorted music (but still recognizable as music) for a few seconds then it goes away (ie goes silent) and stays silent until what happens? I'm just trying to get a good understanding on what you are experiencing. Does the display keep on showing the correct sample rate when it stops?
The badly distorted but recognizable music sounds like the DAC is getting fed the wrong format. The USB interface on this DAC only supports S32_LE (32bit integer) format. If somehow the software is sending something else it would sound the way you describe. The software (player and or OS) is responsible for adding the zeros to convert 16bit or 24 bit to 32 bit. There might be something in either the player or OS configuration that is forcing a different format. (usually the software asks the DAC what it supports and automatically does the conversion, but some software allows that to be over-ridden)
I don't know Macs so I can't advise where to look for this, someone else will have to give advise on that.
John S.
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Hi John,
So I have 2 different behaviors using USB. The first is that I hear some audio, but it sounds like it is digitally clipped... I'm familiar with that sound from my music work. It is recognizable as music, but it sounds like 50% or so of the samples are clipped. I get this sound for about 2 seconds and then the USB device no longer appears on my computer. To get it back I need to power cycle the DAC. That happens with a latest mac mini running Audirvana 2.x.
2nd behavior is when using the DAC as the normal output of the mac. In that case I can select the DAC, but when I try and send any audio, I get no sound and IMMEDIATELY the DAC disappears as a device. power cycle again brings it back. This happens on 2 different macs and with audirvana 1.5.
In all cases, the macs have USB 3 ports. As macs are basically unix, I'm assuming there is a log file I can get to see when the DAC disappears. But I suspect that it is on the DAC side because of the audirvana behavior... it keeps playing as if the DAC is still there. On the mac audio side, the mac sees it disappear and then switches over to internal audio as a default. Maybe some firmware programming went wonky?
I have tried switches in audirvana to force 24 vs 32 bit mode, turn on direct mode, disable integer mode. In the 24/32 case no behavior change. In the others I get no audio at all.
My other XMOS dacs are all fine on the same equipment. I'm not sure if you are using XMOS firmware or something special for the USB async receiver side. But it is unusable for me in any USB configuration.
Tony
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Hi Tony,
Sorry that you are struggling with the DAC. I think the thing to do at this point is for us to issue a call tag and bring it back here for a look see, and get you up and running ASAP.
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Thanks much. The DAC sounds FANTASTIC with my toslink test. It is immediately a dramatic improvement in detail and musicality. I would LOVE to have it happily creating music. Let me know what the process is. I have all the original packaging and can send it soon.
My BeePre is lonely :-)
Tony
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Hi Tony,
Sorry to take so long to get to your DAC, it's been a very busy week. I ran it in our testing setup this morning, along with the four DACs we are shipping out today. I took the most difficult approach I could to try to get it to fail, which is to hot plug to USB with Amarra up and running on the computer. The Mac found the DAC immediately and played all sample rates without distortion. Josh just also tested it on a Win 7 desktop with no issues.
So I guess we will need to figure out what the issue is between the DAC and your computers. We haven't seen what you have described with a Mac ever, but we have seen a similar issue with very new Laptops running Win 8.1. In those cases it had to do with the USB settings in the BIOS, and was solved by disabling booting from USB. Don't know if that is possible on a Mac and I don't have the latest Mac Mini with which to test.
Next we will try loading a trial of Audirvana to see if anything changes.
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Has anyone else tried the BH DAC on usb 3? I've read that usb 2 and 3 are supposed to be compatible but
also that some people have trouble when plugging usb 2.0 devices into usb 3.0 ports.
-Dave
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Has anyone else tried the BH DAC on usb 3? I've read that usb 2 and 3 are supposed to be compatible but
also that some people have trouble when plugging usb 2.0 devices into usb 3.0 ports.
-Dave
Yes I have tried it on a USB3 port and it works fine on one computer and has some problems on another. The correlation seems to be not whether it is USB3, but whether the motherboard uses UEFI (modern BIOS replacement). Some manufacturer's UEFI seem to have an issue. Since newer motherboards are the ones that seem to have USB3 and UEFI it's sometimes hard to tell what is really responsible, the USB3 or the UEFI.
I have a laptop which does NOT have UEFI but does have both USB 2.0 and 3.0 ports, the DAC works fine on both types of ports. I have a desktop that has UEFI, 2.0 and 3.0 ports, all of them have problems. This tends to point to it being a UEFI problem rather than a USB3.0 problem.
The UEFI problem seems to be taken care of by turning off all UEFI USB boot options. The UEFI is supposed to hand over control of all devices to the OS when it starts, it looks like some UEFIs don't completely do that. If the UEFI never talks to USB it doesn't matter.
John S.
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Thanks for the explanation, John.
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thanks Doc!
I'm very curious to see what Audirvana on a mac with USB 3.0 does. All my macs are now newer and have USB 3.0. I know Audirvana takes low level control of USB so it can enable 'sonically good' modes like integer (vs normally floating point approximations are used for data). I tried combos of enabling/disabling features, but nothing worked.
My listening room mac is a 2014 mac mini running latest version of Yosemite OS X. All ports on all my macs are USB 3.0.
I was digging and found some issues with XMOS 2 and USB 3 macs (the Shiit DAC mostly). The solution is to put a USB 2.0 hub between mac and DAC. I have a 2.0 hub if that turns out to be the workaround.
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I realized that my wife's computer is newer than mine, so I checked and it does have USB 3.0 ports. I tried it and the DAC works fine. The computer is a Mid-2012 13-inch MacBook Pro running OSX 10.9.5. Listened for 15 minutes on iTunes 12.1.0.50 before installing the Audirvana demo. Still works fine. Tried both USB ports as well.
Did you ever try just using iTunes, or was all testing done with the same software?
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I tried native mac audio and audirvana. So I must have one of the unstable combos, or maybe latest USB silicon and driver are different? My systems are 2014 and the latest 2015 Broadwell-based macbook pro (kick a$$ machine).
I can put a usb 2.0 hub in the chain. This should eliminate any USB 3.0 port issues. 3.0 can downgrade to 2.0 data rates, but the HW protocol is still 3.0. A 2.0 hub eliminates that issue (assuming the hub is stable talking to a 3.0 port on the mac.
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Sorry to say we don't have a more recent Mac around to try. Our not being able to recreate the issue does seem to point to it having to do with some change made in the more recent models. The other remaining possibility is the OS, as I don't think we have tried it with the latest version.
My son has a newer Macbook. I will ask to try a DAC on that when I see him next, which might be a week or two away.
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The "upstairs" Mac will go to the latest version. Want me to try to break it, Doc?
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Arghh. OK, let 'er rip.
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Alright, after the many hour long joy of installing an OS, I have results.
The DAC runs on an early 2009 MacMini running OSX 10.10.2.
In other words, the DAC is fully compatible with:
USB 3 running on 10.9
AND
USB 2 running on 10.10
Testing has been done with iTunes and Audirvana under 10.9 and VLC and Amarra under 10.10.
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Thanks everyone for looking into this and checking all these options out. I did find several issues with OS X 10.10 and USB DACs with USB3 ports when doing a google search. In one case I found, the same behavior was seen. Here is the text from an audiogon post:
Hi, folks. I "upgraded" my MacAir to OSX Yosemite on Tuesday and now my DAC (Esoteric K-03) won't work properly. Whether on iTunes, Amarra or Audirvana, I get about 15 seconds in before the sound begins to warble, distort, chatter and finally stop altogether. I'm assuming it's a driver issue (there hasn't been an updated Mac driver on Esoteric's website since 2011), but I'm wondering if anyone else has had this problem and if there are any creative fixes anyone has discovered. Thanks!
So at this point, its probably good to send the DAC back to me. I now know it wasn't a firmware, loose connector, etc issue. My solution for now will be to put a USB2 hub in the signal path. This has worked around many of the issues seen on the web. I may get some additional jitter, but as both devices will be async and able to pump data music faster than is ever needed, probably not an issue.
Thanks again for looking into this. I will update the forum on my workaround, and will periodically check operation with the usb2 hub removed to see if some 10.10 update fixes the incompatibility.
As a side bonus, your upstairs mac is not on 10.10 :)
Tony
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OK, will do. I will try a DAC with my son's new Macbook Air when I see him next, and will certainly report if I can reproduce the problem and if we find any clues to a remedy.
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Had I been able to create the failure mode, my first plan to resolve it was to try setting up a firmware password:
http://apple.stackexchange.com/questions/97157/preventing-booting-from-external-media
The reason behind my thinking here is that the problem on Windows 8 has been related to the USB boot option in the BIOS, so the closest I could find to disabling that on a Mac was this. No idea if it will work or not, but if dropping the USB3 to USB 2 via a hub doesn't work, it might be something to try.
I just slapped a label on your box, so you should see it in a few days. Please update the thread if you figure anything out.
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I found the same problem as decribed in this thread when I tried a mac pro cyclinder with usb 3.0 ports.
I used AudioGate as the player. A few seconds after AudioGate plyas a song, the DAC disappears from the list of devices seen
in the audio/midi window. I don't recall any sound coming from the DAC. Rebooting the DAC brings it back as a device.
I have not tried any workarounds. I'm running OSX 10.10.2.
-Dave
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Here is something to try (when my dac arrives I will try this). Several people have reported issues when vt-d is enabled. Here is something I found on disabling vt-d and seeing what happens:
The fix is to disable VT-d by entering the following command in Terminal, then restarting the Mac:
sudo nvram boot-args="dart=0x0"
This change is reversible by deleting the boot-args parameter in nvram, which you can do by entering the following command, then restarting:
sudo nvram -d boot-args
Comment added by Joshua Harris:
Caveat emptor, this solution could cause issues if your startup drive is an SSD. Please research carefully before applying this method to a computer with an SSD.
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I'm experiencing similar issues with a 2014 Macbook Pro Retina with USB 3 ports. Toslink output from the computer is fine, but with USB:
- with Midi Settings at 44.1 khz, 24-bit, the DAC plays garbled music for a few seconds then becomes unrecognized by the computer, requiring a DAC restart.
- with same Midi Settings but using Aroide's system tweak above, the DAC plays for about 30 seconds, still garbled but less so, before the DAC becomes unrecognized. Resetting the tweak restores the original behavior.
- on an older Macbook Pro from 2009 it plays with no problems
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There are 8 models of 2014 MacBook Pros with Retina. Can you be more specific? Also what player? What OS?
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Has anyone tried the USB 2 hub trick yet? Does it work?
Has anyone tried the firmware password?
Are any of you still covered under AppleCare on these machines? Has anyone placed a call in?
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More specifically, my device is:
MacBook Pro (Retina, 15-inch, Mid 2014)
https://support.apple.com/kb/SP704?viewlocale=en_US&locale=en_US
running OS X Yosemite 10.10.2 (14C109)
Players are Plex, iTunes, Spotify (same as on the 2009 machine)
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Several of the machines listed here are old enough that they didn't come with 10.10 installed. It looks like it's pretty simple to roll back if you have TimeMachine backups from before your "upgrade." Anyone care to try?
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I don't want to volunteer my machine for the roll back as its really my day-to-day work machine. I have an older mac pro with usb 2.0
that works fine with the dac and that machine has the audio duties.
I did some searching on the internet a while back and there are a lot of reports of dacs having trouble with usb 3.0. This is across various platforms,
not just recent macs. The most common workaround is the usb 2.0 hub. I haven't searched enough to find a dac manufacturer that "fixed" the
usb 3.0 issues. I believe I have seen reports of some dacs working on usb 3.0 while others did not for the same platform. At some point I could try my
4+ year old emu dac with the modern usb 3.0 mac pro I have.
I don't know if the fault lies in the host or the dac. I'm wondering if the dac has disconnected from the host has the dac "crashed". If it has, is there a way to
use a logic analyzer or some other hardware device to see where it crashed or what led up to the disconnect? I'm sure John does this all the time in his
development.
I don't think this is too serious as long as the usb 2.0 hub workaround works. I love the dac and am very happy with the sound.
-Dave
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There are several options for fixing this. You have chosen one (using a different machine). That works for you, so great. It's the people who don't have that option that we are trying to find solutions for. So far, one solution seems to have not worked, and no other ones have been tried.
We know that it's the combination of 10.10 AND USB 3.0 that causes the issue*. That's why I'm suggesting rolling back for those that can with relative ease. Searching online shows that it is not just our hardware, but other hardware as well. The U in USB is universal; there is a hardware/OS implementation that removes the universality. This is a problem that Apple needs to fix. Do they know they need to fix it? That's why I'm encouraging people to contact Apple if they are still qualifying for the free phone support for a recent purchase; it gets the problem logged in their system.
*The USB 3.0 issues we have encountered on the Windows side have been limited to Windows8, and resolvable with a change in BIOS settings.
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I received my DAC back and have been trying some things out:
- OSX 10.10.3 upgrade did not change behavior
- VT-d fix does not work (same behavior).
- USB2 hub does not work (same behavior).
This might be an XMOS firmware issue or a combo of a firmware behavior and new USB3 chipset/driver. My other DAC has an XMOS front-end and works fantastic with same exact mac and SW to its max of 384Khz. It probably will take a debug version of XMOS firmware and a USB3 protocol analyzer to figure this one out.
I'm going to have to either resurrect a VERY old mac mini (the first one ever) or switch to toslink until something is figured out. But that limits some of my 24/192 source. Crap.
Does XMOS provide a OS X driver? Everyone says one isn't needed, but maybe adding their driver fixes the issue. I believe that only licensed developers can get access to those kinds of things.
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I don't believe it's an Xmos issue at all, but I'm happy to leave a support ticket on our account to see if they have heard anything from other developers. A web search shows that there were some Xmos/USB3 issues around 2010, but they were resolved rather quickly. Josh mentioned that there was a Windows 8/USB3 error, but it's just a Windows 8 and USB booting error, as the error presented itself on both my USB 2.0 and USB 3.0 jacks (I'm in an odd situation where I have a Windows 8 machine that has both jacks).
USB 3.0 is supposed to be backwards compatible, and it looks like it isn't on Apple products. This is something that needs to be addressed with Apple.
I'd be curious if anybody is willing to try the firmware password, as that solved the issue on the Windows 8 end, and may prove successful on the newest Macs as well.
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what is the firmware password? I'm game (and tech savvy). I was going to wipe and downgrade my system to 10.9 anyways so if I brick it, no big deal.
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See this message:
http://bottlehead.com/smf/index.php?topic=7699.msg74852#msg74852
Also, you probably can't take your 2015 box to 10.9; Apple has never supported installing an OS older than the machine. Rolling back the OS at all became much harder once they went to installing the OS through the App Store; looking around it seems like the easy way to do it now is if there's a backup of the old system on your backup drive.
Your 2015 machine has to be within the 90day free phone support since it went on sale in March, so you really, really, really should try calling them about this issue. The software developers will only work on the problem if they know it's a problem. It's up to the users to tell them the problem is there.
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It would help trying to figure out what is going on if someone who has the problem could record the output of the DAC. Not a microphone recording the sound from a speaker, but directly connecting the output of the DAC into the line input of something that can record it, It would really be great if you could record a sine or triangle wave at say something like 400HZ.
It doesn't really matter what the recording device is ( a line jack on a laptop, a separate audio box with line input etc). It is important to make sure that the level of the recording is set so the signal is not overloading the input. The sample rate doesn't matter.
It would be nice if the file format is something I can read on non-macs, such as flac or wav.
There are lots of things I can do to try and debug this, but I don't have any Macs. So in order to debug It I need to have a computer that has the problem. I'm going to have to let you Mac people figure out what causes the issue.
A recording of the distorterd signal will let me know what is happening, which might give a hint as to where it is happening, in the computer or in the DAC.
There are many ways a digital audio signal can be "distorted", without looking at the signal I can't even make a guess as to which it might be.
The XMOS interface is running 32 bit little endian integer, the MAC software is supposed to query the DAC for this information and make sure it sends this format to the DAC. If it is not actually sending this format (for example if it is sending big endian or float) you would get a highly distorted sound. Is there anyone that is familiar enough with MACs to find out what the actual format is that is being sent to the DAC? I know how to do this in Linux but not MACs.
BTW I'm on vacation for another week and a half, so I can't do anything about it right now, but I can read the info on what is happening And maybe make some suggestions.
Thanks,
John S.
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I skimmed the various posts and did not see any mention of the Audio Midi Setup. Maybe one needs to set the AMS output to the BH DAC to 2-channel 32-bit float. I am running my iMac 5K into an older e-Mu 0404 and have had zero problems. On different machines around the house, sometimes my audio component will not handshake with other hardware. It is always fixed by going into the AMS and defining a different sample rate.
There had been issues with one macmini that distorted the sound and the picture (am running HDMI into amp). The easy fix was to change the sample rate via AMS. Sometimes had to reboot the browser when viewing Web content. Since rolling the mini back to Snow Leopard, the problem has ceased. But, when I change from computer output to TV the amp will not do a handshake. Again, I have to go into AMS and change the bit rate.
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I also have no problems with latest Yosemite, USB3 on a 2014 mac mini and 2015 macbook pro with my Gustard X10 XMOS DAC. No issues with my HRT micro streamer DAC (not XMOS-based). So far my only issue has been with the BH DAC.
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I tried turning on the firmware password. This produced the same result as the "disable VT-d" trick: instead of 5 seconds of extremely garbled output, I got about 30 seconds of intelligible music with digital pops and ticks before going unrecognized.
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Has anyone tried Linux on a recent mac with usb 3.0?
If not, I will try it in several days.
Thanks,
Dave
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I tried to downgrade my 2014 mac mini to Mavericks, but I can't. It was shipped with 10.10 Yosemite and you can't downgrade to anything earlier than what a mac was shipped with. I didn't know that. All the info you need to know is here: https://support.apple.com/en-us/HT204319
When I did have USB working on an older mac, USB audio was subtley better than toslink. I prefer USB.
So until this gets resolved, I'm choosing between toslink or using an older laptop for my music source.
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I have experienced this sound in the last week a couple of times. It is always when I start a new CD. I found that switching inputs and back solves this problem. So I'm just careful at the start of a disk. Since I'm at the DAC to put in a new disk it is pretty minor.
It is the DAC as the analog outputs are fine. But it might be some anomaly with my CD player at the start of a disk.
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I tried to downgrade my 2014 mac mini to Mavericks, but I can't. It was shipped with 10.10 Yosemite and you can't downgrade to anything earlier than what a mac was shipped with. I didn't know that. All the info you need to know is here: https://support.apple.com/en-us/HT204319
When I did have USB working on an older mac, USB audio was subtley better than toslink. I prefer USB.
So until this gets resolved, I'm choosing between toslink or using an older laptop for my music source.
I really want to get to the bottom of this. As I mentioned earlier it's tough to try and work through this without knowing what the distortion is. Is there any way at all you can make a recording of the distortion so I can analyze it and try and see what is happening? At this point I'll take anything, use a voice recorder function on your phone to record it, the mic input of a laptop, anything you have on hand. If you have a choice record at a high sample rate if possible.
Thanks,
John S.
Once I have a clue as to what the distortion is I can start trying to figure out what is causing that distortion.
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I have experienced this sound in the last week a couple of times. It is always when I start a new CD. I found that switching inputs and back solves this problem. So I'm just careful at the start of a disk. Since I'm at the DAC to put in a new disk it is pretty minor.
It is the DAC as the analog outputs are fine. But it might be some anomaly with my CD player at the start of a disk.
Hi Grainger,
could you give me some details of the sequence of events that causes the problems for you? What input are you using? What sequence of powering on or off the CD player and DAC is happening? Have you been listening to another input?
Really helpful would be things like: I do A then B it works fine, but when I do A C then B it doesn't.
Thanks,
John S.
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Yes John, It happens after listening for a while and when I close the tray (Philips DVD 963SA using SPDIF output) it sounds very odd. I'll see if I can just open/close the same CD until I get the noise. I have a recorder on my phone, but it is very low quality.
I have also ordered a TOSlink long enough to go to an OPPO CD/DVD player. Once that arrives I will see if it happens there.
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John,
I switched to using an older laptop (Ivybridge based) to work around the issue. The DAC really shines through USB vs toslink and I didn't want to compromise. When I get a chance, I'll hook my 2014 mac min back up and record the sound.
The distorted sound only happens for my using Audirvana. I get that sound for a few seconds and the DAC no longer is recognized. Audirvana uses integer mode of USB audio 2.0 and may be unique. If I try and drive the DAC from the OS X system sound, I get NO SOUND at all and within 2 secs the BH DAC disappears as a device. So the distortion may or may not give you a clue.
What I really want to do is to bring my DAC to work and get some traces on a USB gen 2 protocol analyzer. If I can get some traces, are those useful to you? I know for my team, its hard to use a trace without firmware source and driver source.
Tony
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It hasn't happened to me again. I got the TOSlink and haven't gotten it fished behind my cabinets yet. There is not much room to work with. It will not reach around the front it isn't long enough.
It might not have happened again since I haven't listened more than a couple of hours since it happened. I'll try turning the system on, putting the CD on repeat and give it 4 hours to see. It very well might be the Philips.
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Grainger,
Since you're using a DVD player, which is primarily designed as a video player, it very likely switches back to the 48K family of sample rates whenever it doesn't have a recognized CD in it. Can you look at the sample rate display on the BottleDAC when you open the tray and see what it's reporting?
The Oppo will probably do the same thing.
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Two answers. Paul, I just ran a test today. I went up and opened and closed the player 6 times. The displayed sample rate stayed at 44.1.
John, the above test was after the system played for 5 hours. So it doesn't seem to have anything to do with the player being "hinky" after hours of listening.
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John,
I switched to using an older laptop (Ivybridge based) to work around the issue. The DAC really shines through USB vs toslink and I didn't want to compromise. When I get a chance, I'll hook my 2014 mac min back up and record the sound.
The distorted sound only happens for my using Audirvana. I get that sound for a few seconds and the DAC no longer is recognized. Audirvana uses integer mode of USB audio 2.0 and may be unique. If I try and drive the DAC from the OS X system sound, I get NO SOUND at all and within 2 secs the BH DAC disappears as a device. So the distortion may or may not give you a clue.
What I really want to do is to bring my DAC to work and get some traces on a USB gen 2 protocol analyzer. If I can get some traces, are those useful to you? I know for my team, its hard to use a trace without firmware source and driver source.
Tony
Hi Tony,
so it works fine with another computer? It's just this one Mac Mini that has the problem?
Yes a protocol trace on the machine that has the problem would be a big help in tracking this down.
The BH DAC has been run in integer mode with Audirvana many times without any problem, so I don't think that per se is the issue. It might be some interaction between that and other setting you have that don't exist on other's Mac Minis.
Thanks for sticking with this, I really want to get it figured out.
John S.
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John-
This problem has been traced to ONLY be an issue when running a Mac with 10.10 AND USB 3.0. USB 3.0 works on OS 10.9. OS 10.10 works on USB 2.0. This is an issue with Apple's software. This is why I have been suggesting that those experiencing the issue contact Apple. The DAC that Tony has was tested here on multiple computers before it was ever sent to him. After he encountered issues, he sent it back to us, where we verified it further.
Grainger's issues are completely different from what Tony has been talking about. I believe it is the issue that I encountered and wrote to you about previously (with recordings, that you identified as "[...]is caused by the S/PDIF receiver (either optical or coax) having a signal, but the clock tracking circuit is prevented from tracking because USB uses a fixed frequency clock, when switched to S/PDIF (coax or optical) the buffer is now so far out of whack with the data that it is messed for a while until the tracking mechanism can get synched up.")
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John and Josh,
I don't consider it to be much of a problem. If it bothers you guys we can continue with it. But I'm very happy.
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I'll see when I can find the time to try and get a protocol analyzer hooked up. I'm no expert at these details so I need help from my team (I'm the lowly manager type).
I wouldn't jump to a conclusion that this is exclusively an apple issue. My other xmos dacs work just fine where the bh dac does not. My team at work encounters these interactions all the time and normally it is some subtle disconnect in implementations or different interpretations of a protocol or spec.
I fear that apple changed USB hub chips and there has been a hardware change that is part of the issue. It happens on all 2014 and 2015 macs starting with the Haswell processor versions.
For now I'm back to a mid-2012 MacBook Air to work around the issue and the bh dac works fine. Btw this is USB 3 system running OS X 10.10.3 using the intel hub. On my 2014 Mac mini the sub ports connect through a Broadcom hub chip.
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Thanks Tony, it would be great if you could share any info you may find. Knowing how well the DAC works with every setup but this one combination will hopefully motivate us to work together toward a solution.
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I just saw this thread and started writing in response before I realized it is a few months old.
FWIW, what aroide was describing sounds very similar to what I heard when I upgraded my Mac Mini to OS 10.10.5 - a painfully harsh chopped kind of sound, like the music was literally going through some kind of chopper (intermittently cutting out time-slices). Recognizable as music, yes, but beyond unlistenable.
In my case, after restarting, then being sure Amarra was running, the problem seems to have gone away, though the sample rate display seems to read 44.1 all the time, even when playing higher-res files - I am still trying to test that more thoroughly, though.