[SV_huMMer]

   
Anything that won't need anywhere close to the 5v USB power (that even some motherboards don't send out on all USB ports) 
 
 

Small correction here, if I may.
 
The voltage always remains (at least, should remain) 5V, or within very narrow margins from this (USB specs are +-5%, with some exceptions going down to 4.4v). Otherwise the device will not initialise or will not function properly.
 
What does vary and matters in this situation is current (measured in A(mperes) or mA). Devices that comply with various USB specs, shall provide (or consume) up to a certain current.
 
In USB specs there's a thing called "unit load", and it's 100mA for USB 2.0 and 150mA for USB 3.0. A single device may consume no more than 5 Unit loads (500mA) for USB 2.0, and no more than 6 UL (900mA) for USB 3.0. However, you're absolutely right - even in PC motherboards not all USB ports will provide the maximum current (not voltage) of 500mA.
 
USB OTG specs often provide for a much lower current limits, which render some of the attached devices inoperable due to power (current) limitations. Galaxy S3 is one of the beefiest phones on the market, as it easily allows full-current (500mA) devices to be powered from its OTG connector.

 

[StanD]

  Small correction here, if I may.
 
The voltage always remains (at least, should remain) 5V, or within very narrow margins from this (USB specs are +-5%, with some exceptions going down to 4.4v). Otherwise the device will not initialise or will not function properly.
 
What does vary and matters in this situation is current (measured in A(mperes) or mA). Devices that comply with various USB specs, shall provide (or consume) up to a certain current.
 
In USB specs there's a thing called "unit load", and it's 100mA for USB 2.0 and 150mA for USB 3.0. A single device may consume no more than 5 Unit loads (500mA) for USB 2.0, and no more than 6 UL (900mA) for USB 3.0. However, you're absolutely right - even in PC motherboards not all USB ports will provide the maximum current (not voltage) of 500mA.
 
USB OTG specs often provide for a much lower current limits, which render some of the attached devices inoperable due to power (current) limitations. Galaxy S3 is one of the beefiest phones on the market, as it easily allows full-current (500mA) devices to be powered from its OTG connector.

My Galaxy S3 burned out when plugged into a Bifrost DAC. The replacement blew out, just the same. It was replaced under warranty both times. I've used the second one with a powered USB Hub or OTG Y cable and wall wart without incident. If you do a bit of searching you will see that many people have experienced the same. Other devices work fine with my Bifrost.

 

[SV_huMMer]

  My Galaxy S3 burned out when plugged into a Bifrost DAC. The replacement blew out, just the same. It was replaced under warranty both times. I've used the second one with a powered USB Hub or OTG Y cable and wall wart without incident. If you do a bit of searching you will see that many people have experienced the same. Other devices work fine with my Bifrost.

 
I am sorry this happend to your SIII, however, there's someting wrong with either the BiFrost, or both of your S3s, because with normally designed devices, this should not have happened. Is your Bifrost with the Gen2 USB board?

 

[ProtegeManiac]

  Small correction here, if I may.
 
The voltage always remains (at least, should remain) 5V, or within very narrow margins from this (USB specs are +-5%, with some exceptions going down to 4.4v). Otherwise the device will not initialise or will not function properly.
 
What does vary and matters in this situation is current (measured in A(mperes) or mA). Devices that comply with various USB specs, shall provide (or consume) up to a certain current.
 
In USB specs there's a thing called "unit load", and it's 100mA for USB 2.0 and 150mA for USB 3.0. A single device may consume no more than 5 Unit loads (500mA) for USB 2.0, and no more than 6 UL (900mA) for USB 3.0. However, you're absolutely right - even in PC motherboards not all USB ports will provide the maximum current (not voltage) of 500mA.
 
USB OTG specs often provide for a much lower current limits, which render some of the attached devices inoperable due to power (current) limitations. Galaxy S3 is one of the beefiest phones on the market, as it easily allows full-current (500mA) devices to be powered from its OTG connector.

 
Thanks for the clarification. So in my case when my amp draws power for the LED from my phone it still gets 5v, but at a much lower current?

 

[SV_huMMer]

Thanks for the clarification. So in my case when my amp draws power for the LED from my phone it still gets 5v, but at a much lower current?

The amp gets 5v, and whatver current it negotiates with the host during the usb otg hanshake. The rest depends on the amp's internal cirquitry - how much it sends to the LED etc.

 

[StanD]

   
I am sorry this happend to your SIII, however, there's someting wrong with either the BiFrost, or both of your S3s, because with normally designed devices, this should not have happened. Is your Bifrost with the Gen2 USB board?

Nothing wrong with the Bifrost. If you do some research you will find that Samsung messed up on the design of the S3 and many people have experienced the same. Some have reported that it can work for a while and then out of nowhere lightning strikes it down. A powered USB Hub is life insurance, or use an E18 or similar portable DAC designed not to draw much current. If the DAC draws a lot of current, even if nothing terrible happens, it will drain the battery much faster.

 

[Hungryhoss]

I have the HTC One M8. It sounds brilliant to my ears, unrooted and with stock music player. I think HTC have nailed it.

But for the sake of keeping an open mind - what benefits, if any, would using a USB DAC with it have?

I'm a bit clueless when it comes to DACs - I've used external headphone amps before with various portable sources when I've needed extra volume, but what demonstrable sonic improvements would sticking a portable DAC into my M8 have over the already excellent DAC that it uses? I don't need any more volume - the M8 goes plenty loud.

 

[ProtegeManiac]

I have the HTC One M8. It sounds brilliant to my ears, unrooted and with stock music player. I think HTC have nailed it.

But for the sake of keeping an open mind - what benefits, if any, would using a USB DAC with it have?

I'm a bit clueless when it comes to DACs - I've used external headphone amps before with various portable sources when I've needed extra volume, but what demonstrable sonic improvements would sticking a portable DAC into my M8 have over the already excellent DAC that it uses? I don't need any more volume - the M8 goes plenty loud.

 
Personally, if you don't need an amp to drive the headphone, chances are you don't need a DAC - whatever device you're using now would have to be a really badly designed one to need a DAC for the sake of the DAC itself (my SGS3 sounds a little too dark even compared to my Note, exacerbating my IEM's frequency response, but NeutronMP's EQ can fix the issue as I am willing to accept some compromises for a portable, as long as the system as a whole is compact and the IEMs are comfortable).
 
Now, the reason why you'd need a DAC when you need an amp is because of the lack of a dedicated output stage on mainstream devices. Too high volume settings might have audible distortion, too low and depending on how the software and the integrated audio chip are designed it may work like Windows and you lose a few bits using its own software volume control (this is also one reason why I can accept compromises in other parts of a system where portability and comfort are the primary concerns). When you use a dedicated DAC, chances are it has a dedicated DAC chip and a real output stage that can feed a clean signal into an amplifier. In both my reference system at home as well as my transportable system I use an amp with a DAC in the same chassis, but again for portable use (walking around) I just use smartphones or tablets as putting it up to my ear with an amp-DAC strapped onto it (since the amp-DAC has no microphone pass-through) is just too much trouble. At worst, I just have to bring the phone up to my lips, as I haven't yet located a nice and affordable CIEM-type cable with a mic on it. If I'm going to carry a separate device around for listening while on the move, I might as well get a new DAP as it won't need to be strapped onto a smartphone nor be connected to it with cables.
 

 

 

 

[SV_huMMer]

  Nothing wrong with the Bifrost. If you do some research you will find that Samsung messed up on the design of the S3 and many people have experienced the same. Some have reported that it can work for a while and then out of nowhere lightning strikes it down. A powered USB Hub is life insurance, or use an E18 or similar portable DAC designed not to draw much current. If the DAC draws a lot of current, even if nothing terrible happens, it will drain the battery much faster.

 
This sounds strange indeed... The key question is "how much is much current". I was connecting all sorts of  DACs to my S3, with no lightning strikes, fireballs or ice bolts whatsoever (those include Burson Audio Conductor, Hegel HD11, not to count small bricks like RSA Predator, M2Tech HiFace Dac, iBasso D12 Anaconda etc). As long as the DAC is class-compliant, it cannot  (or should not) draw more than 500mA - which is the kind of current my S3 (intl version) was easily putting out. What version is yours? I've heard there are hardware differences between US and intl versions of S3, so maybe this is the case...
 
However, I do agree with you - power-hungry DACs do drain the battery. That was, BTW, another reason why I switched to Xperia Z1 Compact - you can charge it while using USB DAC, a pretty unique feature.

 

[StanD]

   
This sounds strange indeed... The key question is "how much is much current". I was connecting all sorts of  DACs to my S3, with no lightning strikes, fireballs or ice bolts whatsoever (those include Burson Audio Conductor, Hegel HD11, not to count small bricks like RSA Predator, M2Tech HiFace Dac, iBasso D12 Anaconda etc). As long as the DAC is class-compliant, it cannot  (or should not) draw more than 500mA - which is the kind of current my S3 (intl version) was easily putting out. What version is yours? I've heard there are hardware differences between US and intl versions of S3, so maybe this is the case...
 
However, I do agree with you - power-hungry DACs do drain the battery. That was, BTW, another reason why I switched to Xperia Z1 Compact - you can charge it while using USB DAC, a pretty unique feature.

I have the US version. I'd be surprised if any phone can source 500mA in OTG mode. Most devices can't supply the 100mA and provide a visual warning to the user.
 
http://www.usb.org/developers/onthego/otg1_0.pdf
 
5.1.1 VBUS Output Voltage and Current 
When an A-device is providing power to VBUS on a port, it is required to maintain an output voltage 
(VA_VBUS_OUT) on that port between 4.4 V and 5.25 V, under loads of 0 mA up to the rated per port 
output of the device’s supply (IA_VBUS_OUT min = 8 mA) as long as the rated output of the A-device is 
less than or equal to 100 mA. 
If the current rating per port of the A-device is greater than 100 mA, then the voltage regulation is 
required to be between 4.75 V and 5.25 V, and the A-device is required to meet the USB 2.0 
specification requirements for power providers. 
If the A-device is not capable of providing at least 100 mA on a port, it must be able to detect when VBUS
falls below the value necessary for proper operation of a B-device (VA_VBUS_VLD min). Any voltage 
below VA_VBUS_VLD min shall be detected as a low-voltage condition. 

 

[JaRGoNzZ]

At worst, I just have to bring the phone up to my lips, as I haven't yet located a nice and affordable CIEM-type cable with a mic on it. If I'm going to carry a separate device around for listening while on the move, I might as well get a new DAP as it won't need to be strapped onto a smartphone nor be connected to it with cables.

I believe ultimate ears have made a custom cable with built in mic suitable for mobile phones

http://pro.ultimateears.com/en-us/ue/custom-in-ear-monitors/accessories

 

[ProtegeManiac]

I believe ultimate ears have made a custom cable with built in mic suitable for mobile phones

http://pro.ultimateears.com/en-us/ue/custom-in-ear-monitors/accessories

 
Yes, the 1TF0vi had one, although I can't tell which one it is on that page as none of them seem to mention a mic save for the one on the top right. The connectors on those aren't compatible with my IEM, and I'm also looking for one in clear color as a black cable on that page as well as the one on the TF10vi (in case it's not the same cable) kinda has too much contrast vs my IEM's shell; I even picked up some of the white Sony Hybrids (I had one pair of the black one but it's worn out) so they would sound and look better than the stock tips (not to mention that I got them on eBay for eightpairs of the same size, whereas Aurisonics only sells the tips in a sampler pack).
 

 

[JaRGoNzZ]

Yes, the 1TF0vi had one, although I can't tell which one it is on that page as none of them seem to mention a mic save for the one on the top right. The connectors on those aren't compatible with my IEM, and I'm also looking for one in clear color as a black cable on that page as well as the one on the TF10vi (in case it's not the same cable) kinda has too much contrast vs my IEM's shell; I even picked up some of the white Sony Hybrids (I had one pair of the black one but it's worn out) so they would sound and look better than the stock tips (not to mention that I got them on eBay for eightpairs of the same size, whereas Aurisonics only sells the tips in a sampler pack).

They only have the 1 in black (yeah, the on 1 the top right) and the TF10vi is not listed

 

[ProtegeManiac]

They only have the 1 in black (yeah, the on 1 the top right) and the TF10vi is not listed

 
I've actually considered just making one, basically hacking a cheap headset with a small enough clip-on mic and then braid it around my existing cable (this will be an everyday cable that will get knocked around a lot), wrap it with some kind of tubing from the y-junction to the plug, then have the mic hanging off and clipped on my collar (I barely wear collarless shirts out of the house, and when I do I'm probably wearing a coat or jacket over it), then wire them all up to a compatible plug. Problem is I can't seem to find any compact enough 4-pin ("balanced") TRRS plugs that will be small enough to fit through my phone case, except for  what comes with stock headsets. I pried one open and I couldn't put it back together properly - they don't seem to be designed to be serviceable to begin with (one other problem is that my IEM cable's conductors don't fit through them, even with me carving out a section on the side to accommodate it).

 

[JaRGoNzZ]

I've actually considered just making one, basically hacking a cheap headset with a small enough clip-on mic and then braid it around my existing cable (this will be an everyday cable that will get knocked around a lot), wrap it with some kind of tubing from the y-junction to the plug, then have the mic hanging off and clipped on my collar (I barely wear collarless shirts out of the house, and when I do I'm probably wearing a coat or jacket over it), then wire them all up to a compatible plug. Problem is I can't seem to find any compact enough 4-pin ("balanced") TRRS plugs that will be small enough to fit through my phone case, except for  what comes with stock headsets. I pried one open and I couldn't put it back together properly - they don't seem to be designed to be serviceable to begin with (one other problem is that my IEM cable's conductors don't fit through them, even with me carving out a section on the side to accommodate it).

Diy would be a great idea but I'm not a very hands on person. Can't help u on that. Sorry