[HaVoC-28]

And volume matching is done ?

 

[SilverEars]

No volume matching, but just a quick comparison to see find out what in the signal path that maybe affecting the headphone output.  I find that at all times, it turns out to be the ODAC, so I regard ODAC as a very good value for it's price.  OR SQ/price ratio.  I have not tried super expensive DACs or own any so, I cannot comment how good a DAC can get.  
 
I want to comment that I am speculating that it is the chip my ears may like as the ODAC is using ESS 9023 chip, whereas other DAPs/DACs I own do not.  To me the ESS implentation sounds to have most details and natural tones.  I want to try a more higher end DAC that utilizes the newer 9018 to see how much it scales.  I will write back if I do.
 
I read in another forum that 9023 is $2 each and the designer went for the cheapest components.  The new 9018 is said to be $65 a chip, so I'm curious how it fares.  I believe it's implemented on several DAPs out on the market now.
 
Now I believe DAC is very important in the signal path.

 

[Solrighal]

I'm in much the same boat. I'm happy the O2 is doing all it needs to but I'm not sure about the ODAC because, like you, I have no basis for comparison.

 

[firev1]

I remembered seeing stuff like "digital signals don't distort" yada yada. Fact: ODAC is not completely immune to noisy power supplies. I can get hold of more rigs to demonstrate it but I believe the fact that ODAC has poorish PSRR to be pretty conclusive regardless of setup. Something like the Doodlebug would be a great product with the ODAC. What happened on the blog was the lack of detailing in the test chain he used for the ODAC, if you are on battery all the time, its gonna work but what if you are using PC? or your laptop's usb is BS? or your monitor's hdmi grounds are introducing crud(it may happen)?
 
 
 

 

[SilverEars]

  I remembered seeing stuff like "digital signals don't distort" yada yada. Fact: ODAC is not completely immune to noisy power supplies. I can get hold of more rigs to demonstrate it but I believe the fact that ODAC has poorish PSRR to be pretty conclusive regardless of setup. Something like the Doodlebug would be a great product with the ODAC.
 
 
 

This is at audible level?  I guess usb carries lots of noise.  Have you tried without AC power?  Also, what is doodlebug?  Linear-PS?

 

[firev1]

  This is at audible level?  I guess usb carries lots of noise.  Have you tried without AC power?  Also, what is doodlebug?  Linear-PS?

This http://www.head-fi.org/t/703334/doodlebug-usb-isolator Yes I have tried without AC power and and rigs I'm using have sufficiently clean usb power which measures roughly the same(or a little worse at most) as the below graph. (take note that the graphs are not indicative of the ODAC's true performance as it exceeds the ADC). The signal to noise on rough calculation is approximately -87dbFS  which would be pretty audible.
 
Edit: Tested with my Fujitsu laptop(AC in situation) isolating the ADC side, got pretty clean results with the ODAC. Still got audibly better results as testing was done with monitor disconnected, my monitor is one of those which somehow 'dirties' the USB ground.

 

[adydula]

I  have tested with many other dacs and its very hard to hear any real world difference to me.
 
Being a purist I want the cleanest power for the dac and amp.
 
I would not even think of using a pc with a crappy USB power source???
 
A.

 

[mcandmar]

  This http://www.head-fi.org/t/703334/doodlebug-usb-isolator Yes I have tried without AC power and and rigs I'm using have sufficiently clean usb power which measures roughly the same(or a little worse at most) as the below graph. (take note that the graphs are not indicative of the ODAC's true performance as it exceeds the ADC). The signal to noise on rough calculation is approximately -87dbFS  which would be pretty audible.
 
Edit: Tested with my Fujitsu laptop(AC in situation) isolating the ADC side, got pretty clean results with the ODAC. Still got audibly better results as testing was done with monitor disconnected, my monitor is one of those which somehow 'dirties' the USB ground.

 
I have experience similar issues with HDMI connections injecting noise back over the ground line.  All i have to is wave my oscilloscope probe near my monitor and it picks up its switching power supply loud and clear.
 
I have just built and tested the Doodlbug along side my own Isolating supply and it performs very well indeed, certainly a lot cheaper and neater than my implementation. See pics of finished prototype here http://www.head-fi.org/g/a/872679/beezar/
 
The last image is my current experiment/project, replacing the AC side of my Linear supply with a UPS charging circuit and a sealed lead acid battery. Idea being i will end up with a battery>regulator>isolator>DAC.

 

[SilverEars]

  This http://www.head-fi.org/t/703334/doodlebug-usb-isolator Yes I have tried without AC power and and rigs I'm using have sufficiently clean usb power which measures roughly the same(or a little worse at most) as the below graph. (take note that the graphs are not indicative of the ODAC's true performance as it exceeds the ADC). The signal to noise on rough calculation is approximately -87dbFS  which would be pretty audible.
 
Edit: Tested with my Fujitsu laptop(AC in situation) isolating the ADC side, got pretty clean results with the ODAC. Still got audibly better results as testing was done with monitor disconnected, my monitor is one of those which somehow 'dirties' the USB ground.

How much noise is caused by the monitor relative to the power supply?  It would be nice to find out.  The noise I'm seeing on the graph, is that harmonics?  Or is it from something that output high frequencies?  Wonder how the noise is be created in the power line. I guess the usb line is picking up all the high frequency noise of the circuit around it.  I wonder what would happen if you use a better shielded USB cable, and also USB cable with ferrite bead?

 

[adydula]

The ODAC has circuitry that helps eliminate this noise essentially.....yes using a USB cable with a ferrite bead will help reduce, attenuate or eliminate an HF being indiuced or picked up etc...
 
Remember that all the specs and plots on the designers site were done with "dirty pc usb" power....and it still exceeds what is defined by the designer to be transparent and world class....
 
I took a DC supply, a Lamda commercial instrument supply highly regulated and filtered and did blind listening tests and could NOT hear any difference that was noteable.
 
Again the neat thing about the ODAC is that it performs so well with a variety of PC's...I have used, Gateway, Acer, Lenovo, IBM, Home DIY ASUS, EVGA etc...all work well with the ODAC. Also USB 2 vs USB 2. Your DC power has to be realy crappy to make a real difference and if its that bad then hey....get rid of the crappy pc.
 
A.

 

[firev1]

I'm at least half sure that a battery may be overkill but hey have fun! I would love to do battery power electronics as well. Here is ground pollution from my VGA monitor, not sure about how newer monitors would work. Rig this time is Monitor >Fujitsu Lifebook-> ODAC->ADC-> Adum4160 isolator-> Lifebook. Taking out the monitor gives me a clean spectrum.
 
Maybe the rigs you have been using are cleaner then most but I find that its not the case with some of us which may explain some's negative experiences with the ODAC.Just making a Y cable to inject extra power may not get you the results you really want as you are really concerned with common mode noise which though the ODAC does an okay job, it won't withstand ground loops. Well, whether you believe me ain't my problem so YMMV. 
 
The really bad pollution you see in the previous graph comes from a small switch mode PSU for the Acer. Coupled with the fact that the usb port happens to be exceptionally close to the power input and bam, distortion. In desktops this may come from power built PSUs or you have some crazy graphics(or monitors) or some crappy fans or whatever polluting your usb. 

 

[mcandmar]

"battery may be overkill", nah there is no such thing as overkill

 
One interesting observation i found with USB noise is that my desktop machine i built for gaming with a high end motherboard, power supply, video card, and i7 is actually much noisier than a simple office PC or my HP laptop running off battery. So it seems the more simple the machine with the less going on inside the better, not the machine with the high end parts inside.

 

[adydula]

So are you able to hear any of this while your listening with a set of sensitive headphones or not?
 
Alex

 

[mcandmar]

Absolutely, less distortion and a lower noise floor is always noticeable using headphones or speakers.

 

[adydula]

hmmm....ok firev1 what do you hear??
 
I don't think it necessarily correlates to a simple machine or a system with high end parts...I have been in the PC business since day 1 with IBM and Lenovo.
In development etc...seen LOTS of stuff that I can not still talk about.
 
That said...if you have a crappy USB power supply its most likely due to poor design or rather a poor mechanical setup or design.
 
The way things are routed and wired can make a difference.
 
There is a lot of HF inside a PC chassis but most of can be trapped or eliminated and even if the noise level is still there it can be attenuated with filtering in the external device and or cables...again if done correctly.
 
Being a purist I have only the needed amount of stuff going or attached to a system while listening.
 
You might want to try HDMI cables etc all with ferrite beads if yours doesn't already have them...
 
A.