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Yoshimi Battles Androids and the DACs

cscottrun4it

cscottrun4it

Active Member
I'm trying to find a sensible response to what seems to be a basic question: what happens when I plug a cell phone into an outboard DAC using an USB C cable?

Let's walk the path through, at a high level:

QuBuzz - > Android OS - > .... - > Outboard DAC

The big question is, what happens to the signal during the "...." part of the path? Three options seem possible, off the top of my head.
  1. Between the Android OS and the USB C, the digital signal is processed by the phone's DAC. THIS IS THE PHONE'S DEFAULT BEHAVIOR. It makes wired headphones and connections to analog amplifiers work.
  2. Between the Android OS and a Bluetooth connection, a digital signal is transmitted to the paired Bluetooth device, which has its own DAC that processes the digital signal.
  3. Between the Android OS and the USB C, a ____ signal goes to an outboard DAC.
Is the signal sent to the outboard DAC digital? If so, how does the phone know to do this? If the signal going out the USB C is always analog, is Bluetooth the only way to get a digital signal from the phone?
 
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Crazy Gnome,

I plug a USB C to 3.5 mm cord into the USB on my phone and then into a pair of 10 yr old headphones every night. That DAC has to be working before the headphones would understand anything, right?
 
cscottrun4it said:
Crazy Gnome,

I plug a USB C to 3.5 mm cord into the USB on my phone and then into a pair of 10 yr old headphones every night. That DAC has to be working before the headphones would understand anything, right?
Click to expand...
What phone do you have and what kind of headphones?
 
I have a Samsung s20 and a pair of AKG 240s. Nothing fancy. They sound very, eh. However, the house stereo is a Denon PMA 2000r driving a pair of Pioneer CS-A50s. Really, that's where I think I'm going to get the bang for the buck on a DAC.

I've been screwing around with qubuzz. The HiRes recordings are incredible. I just think they could be more incredible if I ran them through a DAC other than the Samsung's.
 
I have had an external dac for a little over a year now and wouldn't want to do without it. Used to just plug my phone or laptop directly into the amp. The Topping D50s made a big difference in SQ.
 
Thanks for the link... Now I'm even more confused and certain I've been screwed by the cell phone manufacturers.

By the way, love that Miles quote.
 
cscottrun4it said:
Thanks for the link... Now I'm even more confused and certain I've been screwed by the cell phone manufacturers.
Click to expand...
I think your ok. Samsung always near the top on tech so i am sure it is playing the best it can. Most smartphone manufacturers don't care about SQ so they skimp on the quality of the dac.
LG is the only one that targets audiophiles. They have other issues with there phones like software problems and they are fragile but at least they sound good. Lol
 
I believe I found the answer.

CONNECTING A USB DAC
You can use any Android device, given that it runs Android 3.1 or higher, has USB host support and support for isochronous USB transfers in the kernel. You connect the Android device to the DAC using a USB OTG cable to trigger USB host mode...​

In other words, I think the DAC is bypassed!

Sound right?
 
A DAC can't understand an analog signal from a phone or anything else -- the phone's DAC is bypassed as stated above. And yes phone DACs generally sound bad and don't have enough output without distorting horribly.
 
To bypass phone internal dac. Phone has to be OTG compatible and then plug in OTG cable or adapter. You can plug in usb drive or dac (external device). With OTG you have 2 way transfer. (host mode) With regular usb one way transfer. That is how I would explain it.
There are cheap adapters on eBay. Read up on OTG.

The problem I have with this configuration is that you use up your USB port. You can't hook up to charger. So doesn't work as good for full time player. I have OTG adapters for phone and tablet. Both are Samsung but have different USB connectors.
 
I remember looking into setting up android phone for a music server. Finally came to the conclusion that for a home system a cheap laptop made more sense. I want to use my phone while listening to music sometimes.
 
csr4i: Well, a USB DAC basically is just a kind of external sound interface (aka "sound card") and will typically be USB audio device class compliant with corresponding USB device class descriptor (01h for audio devices, iirc) - so when it's connected to some kind of computer plus operating system with USB host functionality, it can be recognised as such (class & revision x (*) compliant USB audio device) and then adressed accordingly by the corresponding generic driver (e.g. usbaudio.sys in case of Windows).

And as rwartner already hinted to above, in case of some devices like smartphone or tablets USB OTG will additionally come into play, if that device can either act as USB host or as slave device, depending on what it's connected to.

Greetings from Munich!

Manfred / lini

*) So far there are/were 1.0, 2.0 and most recently 3.0. More info on all three revisions can be found on usb.org.
 
Also, for what it's worth, those little USB to 3.5mm dongle/adapters, are actually little DACs. So to the OP, when you listen on your headphones, it's a digital signal coming from the phone, converted by the adapter to an analog signal for the headphones.
 
Really? Every dongle that goes from USB C to 3.5 mm has a DAC? Even my $5 dongle?

I think the OTG solution is likely the right solution. I've been digging around about this for the past week. It makes the most sense to me. Why it's not documented more clearly or readily is a mystery, however.
 
Lol - ain't that the truth, and a laptop won't be obsolete in 18 months. But I'm on a mission from god.

I'm trying to turn my phone into a reliable streaming devise for a set of 600 Ohms headphones from 1985 that no one has ever heard of, apparently (Sennheiser HD-425s). Ultimately, I want to connect the phone to an outboard DAC and amp. I'm going to start with the amp. I'm leaning toward a Shiit Asgard 3.

It will be interesting to see what the Samsung DAC does with an amp. It sounds very good, but not great, on my Denon PMA 2000r. For HiRes audio, I think I can do better. The S20 DAC is notorious for shifting center to the right, and it's low end, specially bass drums, is muddy and boomy. The system doesn't have this problem with signals from the TT, R2R, cassette or CD. I'm certain the Samsung is living up to its reputation.

So that's this audio adventure in a nutshell.
 
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