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OLIMEX Usb Isolator

post #1 of 7
Thread Starter 

Hi everybody,

 

Any experience with this product? My Dac doesn't offer a Galvanic Usb input, and so, noise is passed onto the Dac from the computer.

 

I'm looking at a Usb isolator to clean that noise up without affecting the sound. The Olimex looks ideal for £30. 

 

I would appreciate any feedback on the particular model. 


Edited by fluidz - 11/3/13 at 6:35pm
post #2 of 7

Noise is usually generated by a ground loop in your system, have you checked if something is affecting your audio signal? 

 

regarding the USB isolator, some guys claim that the Olimex works well. 

post #3 of 7

First off are you hearing any distinct buzzing or popping noises, or are you just looking to clean up the backround noise as much as possible?

 

A majority of gains comes from disconnecting the USB power supply and feeding the device from a dedicated linear power supply. Second is isolating the ground line from the PC, and third is isolating the two data lines.

 

I've not used, nor can i find a pic of that unit with the heat shrink removed but i'm going to bet the power supply section is less an ideal for feeding an Audio Device.

 

From what i can see googling M1 DAC your unit has its own dedicated power supply with a decent amount of mains filtering so i suspect the USB power feed isnt required for the device to function.  To test that theory i would sacrifice a USB cable by cutting it open and cutting the black and red wire, basically disconnect the power supply lines from the PC. Then connect the cable to your DAC and test A) does it still get recognized by the PC and function, and B) is there any audible difference in backround noise.  I've also seen people suggest using bits of paper inside the plug to isolate the power pins in order to test the above, whatever works for you.

 

The results of the above will give us a better idea of what you need, plain isolator, or isolator with a dedicated power supply.

 

I documented some of my own Isolator build which is more focused on creating a super clean power supply but it may be of interest -> http://www.head-fi.org/t/684459/usb-isolator-build

post #4 of 7
Thread Starter 
Quote:
Originally Posted by mcandmar View Post
 

First off are you hearing any distinct buzzing or popping noises, or are you just looking to clean up the backround noise as much as possible?

 

A majority of gains comes from disconnecting the USB power supply and feeding the device from a dedicated linear power supply. Second is isolating the ground line from the PC, and third is isolating the two data lines.

 

I've not used, nor can i find a pic of that unit with the heat shrink removed but i'm going to bet the power supply section is less an ideal for feeding an Audio Device.

 

From what i can see googling M1 DAC your unit has its own dedicated power supply with a decent amount of mains filtering so i suspect the USB power feed isnt required for the device to function.  To test that theory i would sacrifice a USB cable by cutting it open and cutting the black and red wire, basically disconnect the power supply lines from the PC. Then connect the cable to your DAC and test A) does it still get recognized by the PC and function, and B) is there any audible difference in backround noise.  I've also seen people suggest using bits of paper inside the plug to isolate the power pins in order to test the above, whatever works for you.

 

The results of the above will give us a better idea of what you need, plain isolator, or isolator with a dedicated power supply.

 

I documented some of my own Isolator build which is more focused on creating a super clean power supply but it may be of interest -> http://www.head-fi.org/t/684459/usb-isolator-build

 

Hi, 

 

I was hoping the Olimex would clear up any injected noise as well as act as an isolator.  

Did try removing ground from a usb cable, it took away the ground loop, but also introduced a different type of buzzing noise. 

 

Thanks.


Edited by fluidz - 11/5/13 at 10:14pm
post #5 of 7
Thread Starter 

Haha, my Amp just arrived not long after writing the post above, no ground loop!

 

Happy!

post #6 of 7

Happy ending so.  With the + and - power line disconnected there is still a ground connection via the metal body of the USB plugs / cable shielding, i suspect that was passing through the noise you were still hearing.  An isolator should cure that issue if you should still have it, certainly the version of the isolator i used will.

 

The fact your XLR connection was causing it is interesting, although you have a + and - for the left and right channel, there is also a ground line tied to connector body / cable shielding if applicable so the issue may be an incomplete ground circuit there on either your source or speaker end.

post #7 of 7
Thread Starter 
Quote:
Originally Posted by mcandmar View Post
 

Happy ending so.  With the + and - power line disconnected there is still a ground connection via the metal body of the USB plugs / cable shielding, i suspect that was passing through the noise you were still hearing.  An isolator should cure that issue if you should still have it, certainly the version of the isolator i used will.

 

The fact your XLR connection was causing it is interesting, although you have a + and - for the left and right channel, there is also a ground line tied to connector body / cable shielding if applicable so the issue may be an incomplete ground circuit there on either your source or speaker end.

 

Regarding the new type of noise that started playing with Gnd and 5v disconnected, I found out it was only when the Gnd was disconnected, 5v made no difference, I found Unplugging my speakers from the wall outlet / or powering them on via a switch stops the sine wave noise - Speakers are self powered.

 

I've switched back and forth with the gnd and 5v connected / disconnected, and each time the tape is on the pins, each instrument in music has its own space (dependent of recording quality of course). Basically much cleaner sound. 

 

One small problem, the Dac sometimes randomly disconnects, and the pc fails to recognise it, happens a couple of times a day, I simply reboot the Dac,  I also have to unplug the speakers when I listen via the headphones - otherwise the sine wave noise returns, but imo a small tradeoff for the sound improvement. 

 

If anybody reading this has a Self powered Dac connected to a computer which has a lot of noise, ie gaming machine with a beast of a graphics card installed, try sticking electrical tape over 5v and gnd of your Usb cable and let us know if there is any difference. I bet there will be!

 

Having an Async Usb connection I really wanted to use Usb over Optical for Music listening, hence why all this bother. Optical is perfectly fine for gaming tho.

 

If an isolator could do the same job of disconnecting the Gnd and filtering out computer noise without me having to unplug my speakers I'm sold, but at £30+ its a large price to pay if it only does the same as what I've done here using couple pieces of tape.

 

Even though what I believe to be an improvement I have to admit, it could all be placebo. 


Edited by fluidz - 11/10/13 at 9:35am
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