Direct USB access

Support questions for Neutron Player only.
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wzx
Posts: 23
Joined: Sat Nov 16, 2019 5:53 pm

Direct USB access

Post by wzx » Sat Nov 16, 2019 6:18 pm

Hello,

I've some questions about "Direct USB access":
- when attached an external USB DAC on the phone via type-c connector, the phone 's internal DAC is automatically bypassed or it's bypassed only when "Direct USB access " is on?
- when "Direct USB access " is off, does it mean that the signal output to phone's external USB DAC is analog?
- If it's still digital, why this option?
- when it's on, the music stops shortly after phone goes to idle. How to avoid this? (my phone is Huawei P20 pro)

Thanks in advance,

Zx

blaubär
Posts: 3312
Joined: Tue Apr 02, 2019 6:48 am

Re: Direct USB access

Post by blaubär » Sat Nov 16, 2019 7:20 pm

wzx wrote:
Sat Nov 16, 2019 6:18 pm
- when attached an external USB DAC on the phone via type-c connector, the phone 's internal DAC is automatically bypassed or it's bypassed only when "Direct USB access " is on?
- when "Direct USB access " is off, does it mean that the signal output to phone's external USB DAC is analog?
- If it's still digital, why this option?
USB is a digital interface, not an analog one, so I'm quite sure that the output is always digital, and the internal DAC is always bypassed, and no analog signal is ever coming out of the USB connector. Yes, there are USB-headphones, but you need an adapter for that, and that adapter probably contains a DAC. The commentary below the option says that it allows direct access to bypass OS format limitations - the Direct USB Option has a submenue, accessible by long pressing on the Direct USB Option - I'd guess that you cannot define the things that you can define in this submenue without the level of control available when using direct usb access.
wzx wrote:
Sat Nov 16, 2019 6:18 pm
- when it's on, the music stops shortly after phone goes to idle. How to avoid this? (my phone is Huawei P20 pro)
That the music stops when the phone is idle has also been reported here : viewtopic.php?f=3&t=4642

wzx
Posts: 23
Joined: Sat Nov 16, 2019 5:53 pm

Re: Direct USB access

Post by wzx » Sun Nov 17, 2019 1:31 am

Thanks very much for your prompt response.
Actually what confuses me is that with Huawei P20 Pro, it has a full type-c USB implementation so it does output analog music, it's why with the simple adaptor Huawei CM20 which doesn't have a DAC, I can listen to music with my 3.5mm headphone.
With "Direct USB access" off, I just can't hear any difference between the simple cable CM20 and my external DAC Audirect Beam. So I am wondering if it's the internal DAC which is used. But can an external USB DAC accept analog signal?
I've also tested with Poweramp, which detects "Wired Headset/Aux", not "UAB DAC" when I plugin my Beam, just like with the CM20.
When I set both "Direct USB access" and "DSD, DSD over PCM" on, and play DSD file, the Beam's DSD light is on, meaning it's receiving digital signal for sure. In any other cases, it indicates playing "PCM", which is also digital.
So totally confused as it's detected as wired headset.

Thanks,

Zx

wzx
Posts: 23
Joined: Sat Nov 16, 2019 5:53 pm

Re: Direct USB access

Post by wzx » Sun Nov 17, 2019 1:44 am

Just more information :
When I plugin the Huawei CM20 with my headset, Android gives a notification that "Type-C analog headset connected".
With Audirect Beam, it says "Uncertified Type-C digital headset connected".
The Beam is not certified by Huawei, but at least it's seen as digital.

blaubär
Posts: 3312
Joined: Tue Apr 02, 2019 6:48 am

Re: Direct USB access

Post by blaubär » Sun Nov 17, 2019 4:53 am

Yes, you're right, USB-C can transfer analog signals : https://www.soundguys.com/usb-audio-explained-18563/

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