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Can a USB powered DAC, headphone amplifier, etc. filter out power supply noise from the USB line?

post #1 of 17
Thread Starter 

I am thinking of upgrading to audiophile grade equipment. Mostly to watch music videos on my big-screen flat-panel television. I have a 82 foot USB extension cable with its own far end power supply. This is what gets my music videos from my computer to my sound system. If I replace my present sound system with a USB DAC, headphone amplifier, etc. does this type of equipment have provisions to filter out power supply noise from the USB connector?

post #2 of 17
USB is digital - there is only the timing and the data packets. What noise are you talking about? If there is noise on the USB, then wouldn't it just cause resends or data drops?

I'm not quite understanding the point of the 82 foot USB connection. Wouldn't a network streaming device that could pull the media directly off a shared folder be better?
post #3 of 17
Thread Starter 
Quote:
Originally Posted by billybob_jcv View Post

USB is digital - there is only the timing and the data packets. What noise are you talking about? If there is noise on the USB, then wouldn't it just cause resends or data drops?

I'm not quite understanding the point of the 82 foot USB connection. Wouldn't a network streaming device that could pull the media directly off a shared folder be better?

OK
perhaps I can better explain. I perceive the digits going over the USB 82 foot cable are arising at the other side with good data integrity and rightly or wrongly I am not worried about quality of the data on the 82 foot cable degrading the music on the video playing on my computer due to data  losses. The reason I'm using and 82 foot cable is I wish to use one computer for web browsing and television watching on my big-screen television.

 

 I was understanding rightly or wrongly that some DAC's and headphone amplifiers and what every else audiophiles use to drive headphones are sometimes powered, I mean DC Voltage powered, over the USB connector and not plugged in to your AC house current. I was thinking that perhaps noise, I mean DC Voltage  noise from the way these devices are being powered DC Voltage  wise, can creep in to the audio output from the way these devices are powered. I thought perhaps if there was some sort of DC purification or extra filtering or regulation of the DC Voltage  coming over the USB connectors those DACs, headphone amplifiers, etc. would have better audio, I mean lower noise.


Edited by bbmiller - 1/31/14 at 1:36am
post #4 of 17
OK - I think I understand - and I don't know enough about USB power supply circuits to answer the question. There are probably capacitors in the circuit that are intended to clean-up the incoming power and provide a voltage supply that can handle peak demands. This might be a question better suited for the head-fi DIY forum, or for the propeller heads over at http://www.diyaudio.com/
post #5 of 17

Yes, USB DACs and headphone amps can typically filter out power supply noise. Some are better at it than others. I don't know how much noise that monster USB cable would cause, but if you find that it is noticeable, here's something you can try [credit to member zilchm0d]:

LL
LaCie USB DualPower Sharing Cable for Rikiki - closeup of "tape" mod

This will allow you to power the hot pin of the USB from a battery. I suppose you would also need some kind of female to female adapter to connect the splitter to your 82 foot USB cable. 

I have done this with my USB DAC and laptop. I didn't hear any noticeable improvement, but I'm using a short USB cord and my laptop's noise on the power line must be well within my DAC's filtration abilities. Someone who had a laptop with terrible USB power found that it made an improvement. Depending on which Anker model you pick, the battery and cable will run you around $50 or $60. 

I would just try a USB DAC without this setup first, and if you have problems, this would probably fix them. 

post #6 of 17
Thread Starter 
Quote:
Originally Posted by manbear View Post
 

Yes, USB DACs and headphone amps can typically filter out power supply noise. Some are better at it than others. I don't know how much noise that monster USB cable would cause, but if you find that it is noticeable, here's something you can try [credit to member zilchm0d]:

LL
LaCie USB DualPower Sharing Cable for Rikiki - closeup of "tape" mod

This will allow you to power the hot pin of the USB from a battery. I suppose you would also need some kind of female to female adapter to connect the splitter to your 82 foot USB cable. 

I have done this with my USB DAC and laptop. I didn't hear any noticeable improvement, but I'm using a short USB cord and my laptop's noise on the power line must be well within my DAC's filtration abilities. Someone who had a laptop with terrible USB power found that it made an improvement. Depending on which Anker model you pick, the battery and cable will run you around $50 or $60. 

I would just try a USB DAC without this setup first, and if you have problems, this would probably fix them. 

The 82 foot USB cable I was referring to is a "monoprice 82ft 25M USB 2.0 A Male to A Female Active Extension / Repeater Cable Product ID 7644" and can be powered at the far end with a optional power adapter of the proper barrel size and voltage which is 5 volts. I am wondering if there are power adapters of sufficient quality that they would introduce no noise that could not be filtered out? At the moment I have the far end of that cable going to a powered hub which also might have an extra high quality power adapter available for it. I guess I could do something like continue to use a power hub on the far end whether or not I hub out to more than one USB device. I could then cover the power pin going to the USB hub and continue to power the repeat a portion of my USB 82 foot cable. So it would be a matter of finding an extra high quality low noise 5 volts power supply to power the USB hub. Do any of you all know anything about whether or not extra high quality power adapters are available?


Edited by bbmiller - 1/31/14 at 11:08am
post #7 of 17

If you can power the hub from a USB port, one of those Anker batteries might do the job. They output 5V / 2A. Or here is another USB power supply: http://www.ab-system.hk/index.php?route=product/product&product_id=64 

Teradak has a lot of other power supply products as well. 

I am not sure if this answers your question. 

post #8 of 17
Thread Starter 

Thanks manbear
I do not know if I will turn out to want to buy one of those you link to, but it is turning out to be a good starting point for keywords to search on.

post #9 of 17
Quote:
Originally Posted by billybob_jcv View Post

USB is digital - there is only the timing and the data packets. What noise are you talking about? If there is noise on the USB, then wouldn't it just cause resends or data drops?

I'm not quite understanding the point of the 82 foot USB connection. Wouldn't a network streaming device that could pull the media directly off a shared folder be better?

 

 

Quote:
Originally Posted by bbmiller View Post
 

Thanks manbear
I do not know if I will turn out to want to buy one of those you link to, but it is turning out to be a good starting point for keywords to search on.

 

The USB standard limits line length to 5 meters (a little over 16 feet).  The primary reason for that is that the USB standard includes 5VDC power.  With that little voltage to begin with, a length over 5 meters begins to have serious voltage drop issues (in the context of 5V total).  There are many USB "booster" cables available.  These are specifically designed to compensate for the voltage drop.  A powered USB hub is not.

 

Beyond that, there is the entire question of USB power quality relative to audiophile quality requirements.  Any high-quality, audiophile-like device that uses USB will need to have it's own power supply or a guaranteed linear-regulated separate power device.  There are such things available.  Some are quite expensive, such as the iFi device.  Like many things that are overly-expensive when first-released, there is also a DIY alternative. ;)

post #10 of 17

Edit - I should qualify that post above:

 

There are two issues that you're talking about:

1. Voltage drop compensation over an extended length USB cable.

2. Audiophile-quality power on the USB bus.

 

AFAIK, there are no solutions that cover both.  You need to buy the USB length-booster cable, first.  They are available if you use the proper search words.  I bought one at Frys years ago that was good to 30+ feet, I believe.  One of these cable-boosters is good for basic USB operation over the lengths specified.

 

Audiophile-quality is an entirely different matter.  Audiophile-quality in almost all instances means a "linear-regulated-power-supply."  That's distinguished from the most common power supply in use today, commonly known as a "switcher power supply."  A switcher power supply is adequate and cheap in all aspects, except for audio quality.  The basic power supply in a PC is a switching power supply, for instance - so is the adapter on any laptop or the charging adapter for a cell phone.  However, none of those is adequate for truly high-quality audiophile sound.  A "linear" regulated power supply uses a voltage regulating circuit that depends on the wasting of voltage - in terms of heat - for achieving regulation.  The results are most similar to battery power, but at the price of voltage and great amounts of heat (relatively speaking).

 

A typical linear-regulated power supply will be much larger than switching power supplies and will contain many slots for ventilation and cooling.

post #11 of 17
Thread Starter 
Quote:
Originally Posted by tomb View Post

Audiophile-quality is an entirely different matter.  Audiophile-quality in almost all instances means a "linear-regulated-power-supply."  That's distinguished from the most common power supply in use today, commonly known as a "switcher power supply."  A switcher power supply is adequate and cheap in all aspects, except for audio quality.  The basic power supply in a PC is a switching power supply, for instance - so is the adapter on any laptop or the charging adapter for a cell phone.  However, none of those is adequate for truly high-quality audiophile sound.  A "linear" regulated power supply uses a voltage regulating circuit that depends on the wasting of voltage - in terms of heat - for achieving regulation.  The results are most similar to battery power, but at the price of voltage and great amounts of heat (relatively speaking).

 

A typical linear-regulated power supply will be much larger than switching power supplies and will contain many slots for ventilation and cooling.

I believe I've read examples of audiophile setups which included an external power supply. Could you or anybody names of equipment, links, or pictures of audiophile quality headphone driving equipment that either incorporates the linear power supply you recommend or has provisions to be powered externally. Also I am wondering if there can be a very high frequency switching power supply which will be all the same to me when powering my headphone set up. I am a 63-year-old man and fear I may have some high-frequency hearing loss. When I equalized what probably is a less than audiophile quality headset I began to get the best music listening I have ever had in my life. However I was not able to equalize to hear frequencies above 12 1/2 K. So I am wondering if the switching frequency of a switching power supply was high enough in my set up if it would be all the same to me.

post #12 of 17

I find Apple USB chargers to be very clean and somewhat cheap.

 

A properly designed power supply should work at frequencies far above human hearing.

 

Something like a Fiio E07 will let you turn off USB charging when you're listening, so it runs off battery power which won't suffer from noise.

post #13 of 17
Thread Starter 
Quote:
Originally Posted by higbvuyb View Post

 

A properly designed power supply should work at frequencies far above human hearing.

What about switching power supplies that keep the noise frequency far above human hearing.  Do they exist?

post #14 of 17

I wouldn't bother.

post #15 of 17
Quote:
Originally Posted by bbmiller View Post
 
Quote:
Originally Posted by tomb View Post

Audiophile-quality is an entirely different matter.  Audiophile-quality in almost all instances means a "linear-regulated-power-supply."  That's distinguished from the most common power supply in use today, commonly known as a "switcher power supply."  A switcher power supply is adequate and cheap in all aspects, except for audio quality.  The basic power supply in a PC is a switching power supply, for instance - so is the adapter on any laptop or the charging adapter for a cell phone.  However, none of those is adequate for truly high-quality audiophile sound.  A "linear" regulated power supply uses a voltage regulating circuit that depends on the wasting of voltage - in terms of heat - for achieving regulation.  The results are most similar to battery power, but at the price of voltage and great amounts of heat (relatively speaking).

 

A typical linear-regulated power supply will be much larger than switching power supplies and will contain many slots for ventilation and cooling.

I believe I've read examples of audiophile setups which included an external power supply. Could you or anybody names of equipment, links, or pictures of audiophile quality headphone driving equipment that either incorporates the linear power supply you recommend or has provisions to be powered externally. Also I am wondering if there can be a very high frequency switching power supply which will be all the same to me when powering my headphone set up. I am a 63-year-old man and fear I may have some high-frequency hearing loss. When I equalized what probably is a less than audiophile quality headset I began to get the best music listening I have ever had in my life. However I was not able to equalize to hear frequencies above 12 1/2 K. So I am wondering if the switching frequency of a switching power supply was high enough in my set up if it would be all the same to me.


The iFi device is a linear-regulated supply, but it's extremely expensive.  HiFimeDIY has a USB isolator that they claim has an improved power supply, but it is not powered externally, so performance can't be dependable.  There is an inexpensive DIY solution in the works, but I'd be accused of shilling if I spoke about it in detail.  There is information in the DIY section.  Another user on Head-Fi - mcandmar built his own device awhile back with proven results.  Other than these, I'm not aware of another truly audiophile solution.

 

Switching power supplies are often very noisy.  They claim to have "pushed" the noise well above the audible threshold, but there are many artifacts, phase distortions, etc., that cause harmonics into the audible band.  Let me emphasize, however, that "noise" in the power supply is rarely something that's heard.  Instead, it's a general lack of quality in sound: maybe a glare in the high-end, a general loss of dynamics, sloppy bass, etc.  It simply causes effects that result in sounding blah vs. GREAT.  Only extreme examples - not worthy of any consideration at all - result in noise that's directly audible in the sound signal.

 

Also, switching power supplies can sometimes be used with amplifiers (including headphone amplifiers) with good success.  However, every amplifier circuit has a calculated property known as PSRR - Power Supply Rejection Ratio.  It's a measure of how much noise in a power supply will affect the amplifier circuit itself.  Good circuits have very high PSRR's.  However, powering a source such as a DAC does not qualify.  Once noise is introduced, it'll propagate throughout the signal stream.


Edited by tomb - 2/2/14 at 5:54pm
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