Astell&Kern XB10 Extreme Bluetooth Adapter
Oct 8, 2017 at 12:24 AM Post #331 of 457
Mm...currently using the XB 10 when I am using Apple TV (4th gen): with my CIEMs and the Audioquest Nightowl Carbon, for very late-night Netflix when everyone is asleep and I do not want to disturb them. Love it. Dialogue is much easier to understand.
 
Oct 16, 2017 at 12:14 AM Post #332 of 457
Has anyone tried to use their XB10 while charging? I'm very curious because I would like to use it in my car as well as for headphones, and the battery life is kinda... short.
 
Nov 5, 2017 at 12:24 PM Post #336 of 457
The thread is very long, so I haven't read it all but... regarding the AAC "untouched" through iOS, I wonder. I used to be an iOS user but not anymore, so I can't test it. But I expect that the OS is capable of sending audio cues during music reproduction, for notifications, etc. If it does that, it means that the sound goes through the internal software mixer and *then* is recompressed to AAC for transmission.

So I would be surprised if they manage to send straight AAC files from Apple Music, unless playing those back stops all other system sounds from reaching your headphones.

I can verify that iOS does, in fact, send notification sounds while playing my AAC tracks directly from the Music app. I am connected to my Sound Blaster E5 (which supports AAC) over Bluetooth from my iPhone 8 Plus, and I just now heard a notification sound play over my AAC track -- it lowered the volume of the track to play over it but the track was playing in the background, just at a lower volume -- then after the notification sound, the track volume went back to normal.

I suppose it could very quickly swap from sending the untouched AAC stream to a mixer-ed version of it, and disguise the sleigh of hand since it's lowering the volume of the AAC track anyway while it's sending the mixed audio. But I've also had this question and have yet to find a satisfactory answer as to whether an iOS device is ever sending the raw AAC stream or recompressing it always in order to maintain that mixer function.
 
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Nov 12, 2017 at 11:29 AM Post #337 of 457
I suppose it could very quickly swap from sending the untouched AAC stream to a mixer-ed version of it, and disguise the sleigh of hand since it's lowering the volume of the AAC track anyway while it's sending the mixed audio. But I've also had this question and have yet to find a satisfactory answer as to whether an iOS device is ever sending the raw AAC stream or recompressing it always in order to maintain that mixer function.
If it's doing this in a gapless/seamless way, my money is in recompression happening all the time.
 
Nov 14, 2017 at 9:42 AM Post #338 of 457
But I've also had this question and have yet to find a satisfactory answer as to whether an iOS device is ever sending the raw AAC stream or recompressing it always in order to maintain that mixer function.

If it's doing this in a gapless/seamless way, my money is in recompression happening all the time.

AFAIK all bluetooth A2DP transmission is packet oriented. Since splitting and reassembling VBR files is no trivial task, I'd assume there's recompression happening all the time.
 
Nov 14, 2017 at 9:45 AM Post #339 of 457
AFAIK all bluetooth A2DP transmission is packet oriented. Since splitting and reassembling VBR files is no trivial task, I'd assume there's recompression happening all the time.

Thanks, that makes sense to me. I was having difficulty believing the claims of people who were touting AAC codec over BT as somehow not lossy if the original files being streamed are AAC, e.g., from Apple Music or local AAC files on the iDevice, because of the experience I was hearing with notification sounds being clearly mixed in.
 
Nov 24, 2017 at 12:11 AM Post #340 of 457
Astell & Kern introduced a firmware upgrade for the AK3xx series units in October (included in the upgrade from 1.12 to 1.20 firmware for the AK320) that allows them to send aptX HD Bluetooth information to the XB10 and other devices that incorporate the Qualcom aptX HD chipset. Only problem is the firmware upgrade did not contain an option switch to allow the AK3xx units to send either the older aptX Bluetooth codex info or the newer aptX HD info. Receiving devices that do not have the aptX HD chipset will have issues talking to an AK3xx device. In my case a Bose Soundtouch 30 III speaker worked fine with the 1.12 firmware that sent aptX info but does not work with the 1.20 firmware that supports aptX HD. Seems like a shame to have to purchase a $189 item to use an older device when AK has the software for both options and could have included this in the firmware. I have made AK USA support aware of the issue. Will be interesting to see how they respond.

WAS55
AK released the 1.21 firmware for the AK320 a few days ago. Although not stated in the release notes, AK have fixed the bluetooth compatibility issue with Bose speakers that I wrote about almost exactly 1 year ago. I installed the new firmware and my AK 320now streams perfectly to any of a Soundlink 30, a Soundlink 10 or a Soundlink Revolve.
 
Nov 27, 2017 at 2:16 AM Post #341 of 457
Anyone interested in picking up an XB10, they're $99 USD everywhere right now, including A&K's website. I almost pulled the trigger a couple of days ago on Amazon when it was sitting at $108 and change. Glad I waited. :)
 
Nov 29, 2017 at 5:37 AM Post #344 of 457
So if I’m understanding this correctly, only the Apple Music app itself uses AAC for Bluetooth? What do Tidal & Spotify default to on IOS?
As far as I know all services use either SBC or AAC on iOS products. Because it's independent from the service decision. Spotify streams Vorbis, IIRC, it gets decoded on your iOS device and then sent via Bluetooth using either SBC or AAC (with AAC being preferred by being the more advanced codec of the two).

As we've been discussing, all indicators point to AAC never being sent directly through. Even when music is originally encoded in AAC format (such is the case for Apple Music). This is because the device needs to mix in system sounds. But you can read about this above.
 
Dec 4, 2017 at 12:37 PM Post #345 of 457
Has anyone ever seen any detailed tests with an aptX HD source? I just ordered on to try for my car audio with Pixel 2. Will report back once I get it.

p.s. WorldWide Stereo still has them at $99 Black Friday price.
 

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