[Spiral Out]

   
Thats the basic kit i used in my build, but you dont want to use that power supply, you will need a decent linear one.  You can buy that kit without the power supply parts here http://www.circuitsathome.com/products-page/usb-interfaces but to be honest you would be better off waiting for Tomb to finish his isolator/power supply kit and buy that instead.

The Doodlebug looks very interesting. What would be the advantage of the Doodlebug over the isolator I mentioned with a linear power supply?
 
Also I have never built anything on a pcb board. My only soldering experiance is repairing/building cables. Is an isolator difficult to build? One of the main reasons I was interested in the circuitsathome.com board was that it was pre built.

 

[00940]

  The Doodlebug looks very interesting. What would be the advantage of the Doodlebug over the isolator I mentioned with a linear power supply?
 
Also I have never built anything on a pcb board. My only soldering experiance is repairing/building cables. Is an isolator difficult to build? One of the main reasons I was interested in the circuitsathome.com board was that it was pre built.

 
The circuitsathome isolator and the doodlebug are very similar. However, the regulator used in the doodlebug is a linear one, while the circuitsathome usb isolator uses a switcher which is not particularly low-noise. Which led someone to hack the board: http://www.circuitsathome.com/measurements/linear-power-supply-on-usb-isolator-board
 
The doodlebug will also accept ac inputs, the other one is dc only.

 

[DNICE1]

I have been using an ODAC for a few weeks now and my experience is that when I connect it to the USB 2 port of my Asus Core i3 laptop the top end is slightly more prominent but very clear and sounds good connected to my CA 840A amp and B&W 685 speakers but when I connected the ODAC to my A1 amp with DT880 600 the treble becomes uncomfortable after half an hour.

So I bought this power supply and modded the usb cable to use the external power and the treble is now sweet and not fatiguing anymore with the DT880. So in my case the external linear power injection has made real difference and the ODAC sounds exceptionally good with my headfi now.

http://uk.rs-online.com/web/p/embedded-linear-power-supplies/0592076/

BTW, I didn't pay the full price for this power supply got it really cheap in an auction.

 

[mcandmar]

As above, the Doodlebug is the same isolator chip but with a nice power supply built onto the same board, and ultimately will all fit inside a nice enclosure.
 
Quote:

http://uk.rs-online.com/web/p/embedded-linear-power-supplies/0592076/

BTW, I didn't pay the full price for this power supply got it really cheap in an auction.

 
Interestingly, i just bought one of those boards from eBay last night to experiment with. What really caught my eye was the provision of a battery connection on it which would make a super quite power source, i'm thinking of using it to charge a 12v lead acid battery, then disconnect the mains and run off the battery pack for listening to music.  I will still use the low noise linear power supply i built, just with this unit & battery sitting in front of it.  I have no idea how good the regulator on that board is until i get the unit and test it, but at worst i will only use it as a battery charger circuit.

 

[MaciekN]

As stated on "the blog" ODAC does not need galvanic isolation to perform D/A conversion with no audible artifacts. Otherwise it would imply that the guy who designed it got it all wrong and doesn't know how it works. This especially relates to linear power supply - with the right (not necessarily expensive or complex) filtering modern switch mode power supplies can provide nice and clean enough power. Also remeber that ODAC has a built it 3.3 V power supply regulator.
 
You don't need to buy anothing extra to enjoy the sonic performance of this unit, that is how it was designed.

 

[gr34td3str0y3r]

My Odac no longer works with my main computer. I just came home from a long trip. I got back and my anti virus updated, flash, windows had 18 updates when I reset. I installed foobar and an adiational USB dac for my home theatre. 
Then my ODAC stopped working propably. I tried deleting foobar and the driver for the other USB dac. no good. 
JDSlabs has no idea, they said they have never heard of this. 
It is like the ODAC has the volume turned WAY down on the lower 2/3 of the frenuqncey range. The top 1/3 of sounds just fine. 
I plug it in, out. Nothing. Sometimes I try and it just works. I go to the other room come back. Messed up again. 
I tried it on my wifes computer and it works. I know it has something to do with drivers and all the updates I did in one sitting. 
I have no restore point. Do I really have to re-install just to get my ODAC working. 
To make matters worse I have a Japanese computer. I can do 98% of what I need to on this computer just fine. Now trying to track down drivers and messing around with system menus, the register, and error messages, that is the 2% that I can't do. 
NUTS! Just got my Fidelio X1s and can't even use my ODAC and O2 set up. 

 

[DNICE1]

As stated on "the blog" ODAC does not need galvanic isolation to perform D/A conversion with no audible artifacts. Otherwise it would imply that the guy who designed it got it all wrong and doesn't know how it works. This especially relates to linear power supply - with the right (not necessarily expensive or complex) filtering modern switch mode power supplies can provide nice and clean enough power. Also remeber that ODAC has a built it 3.3 V power supply regulator.

You don't need to buy anothing extra to enjoy the sonic performance of this unit, that is how it was designed.

I am not at all implying that the designer got it wrong, all I am saying is that in my hifi setup I quite like the sound when ODAC is connected directly to my laptop and drawing power from USB (maybe the amp and speakers are a little warm sounding) but in my headfi setup the treble becomes too fatiguing quickly, this probably has more to do with either the character of the A1 amp/DT880 and the noisy USB power from my laptop but nonetheless, I can clearly tell a difference in top end with and without the linear power supply, it's quite distinguishable.

The linear power supply in my case does tone down the top end a little but still not enough to my own liking for my headfi setup so out of curiosity, I have ordered an O2 from Epiphany Acoustics just to compare it with the A1. Maybe that will fix the problem if not then HD650 will be next on my upgrade list.

 

[DNICE1]

I have no idea how good the regulator on that board is until i get the unit and test it, but at worst i will only use it as a battery charger circuit.

I will be interested in your tests of this power supply.

 

[MaciekN]

DNICE1 try a quick test - see if there is any sonic difference when running your laptop off battery vs power line. This should make a lot more difference than with that beefy external PS.
 
Do report back when you get the O2 - it would be very interesting to know if it takes away the unpleasant treble. Anyne knows the PSRR figure for the A1?

 

[DNICE1]

MaciekN that's how I always listen to music if using USB with the switching power supply disconnected and laptop running on battery.

I will report back once I have the O2 and have compared it to the A1 to see if makes any difference.

 

[DNICE1]

DNICE1 try a quick test - see if there is any sonic difference when running your laptop off battery vs power line. This should make a lot more difference than with that beefy external PS.

Do report back when you get the O2 - it would be very interesting to know if it takes away the unpleasant treble. Anyne knows the PSRR figure for the A1?

While reading this thread http://www.head-fi.org/t/703334/doodlebug-usb-isolator/105 a guy built and tested a USB Isolator called Doodlebug with an ODAC and not surprisingly got the exact same results which I did, check post #108 on page #8

 

[MaciekN]

Yes, nice. Now, pay a tribute to ODAC's designer and go measure it before and after after inserting external PS into the system, then compare the results with your subjective impressions, I'm sure that the whole community will appreciate your efforts. I, for one, am very eager to see your findings.
 
BTW is there a change to the sound when your laptop is running off the mains and ODAC uses USB power? If so, how would you describe it?

 

[tomb]

Well, PCB's have been ordered and I hope to have things done sometime in April. Keep in mind that this is a team effort with the primary designer, Avro_Arrow.

 
Those of you that follow the ODAC may have learned to despise RMAA, but if used for direct comparison rather than absolute measurements, I don't think you can fault it:
 
Noise Level

 
Dynamic Range

(note that RMAA uses a 1K carrier signal, hence the spike anomaly)
 
More details are available on the DIY section of the Head-Fi, but I don't want to risk the accusation of doing nothing but shilling.
 
The PupDAC is admittedly, a Beezar product.  However, it is a quite sophisticated USB-powered DAC, having as many as 5 separate regulators onboard in addition to numerous electrolytic power caps. The USB for the DAC communicates via the TI PCM2706/7 chip, which is limited to only 16-bit/48kHz, maximum.  The DAC chip is a TI PCM1794, which is rated to -129dB S/N in stereo configuration.  Nevertheless - except for the tiny spikes, one can see that the total DAC implementation is less than -125dB S/N for pretty much everything from 300Hz to 20kHz.  (Oops!  That was an absolute reference.

)
 
Anyway, whether the DoodleBug provides a benefit depends on the power supply inherent on a USB-powered DAC's PCB.  For those DACs with few or no regulators, little performance improvement will be seen.  (Low-fi is still low-fi, IOW.)  For those DACs that are more sophisticated and include many regulators on the PCB, it will provide an improvement by ensuring sufficient voltage for the regulators to be within their regulating regime, if nothing else.  Some regs operate super-close to the bottom tolerance of USB voltage.  If there's not enough voltage available on the USB buss, they're not going to regulate as designed.
 
Other USB isolator products do not provide a completely separate, linear-regulated power supply.  The DoodleBug will definitely be superior to those.  Similarly, as for USB hubs, I am not aware of any - including the Belkin - that uses a true, linear-regulated power supply ... except for the $200 iFi iUSB product.  Except for the iFi, they will all add to the distortion in the USB power supply for an audiophile device.
 
In the tests that I've conducted through the years, it is absolutely amazing how poor USB power is, relative to audiophile needs.  Laptops and docking stations are absolutely atrocious.  Desktop/towers are very little better, except that the DAC may not knock offline as much due to irregularities in the USB stream.  One might go so far as to say the difference between a low-fi DAC and mid-fi/hi-fi DAC is whether it is USB-powered or not.  The DoodleBug can correct that.

 

 

[DNICE1]

Yes, nice. Now, pay a tribute to ODAC's designer and go measure it before and after after inserting external PS into the system, then compare the results with your subjective impressions, I'm sure that the whole community will appreciate your efforts. I, for one, am very eager to see your findings.

BTW is there a change to the sound when your laptop is running off the mains and ODAC uses USB power? If so, how would you describe it?

I think that the ODAC is a great sounding DAC and I am all for objectivity but in my experience with the ODAC with my own gear I am convinced that it can benefit from a good linear regulated PS to tame that little fatiguing top end. I would love to measure the change before and after the external PS if I could afford some decent test equipment but I can't so for the time being I would have to use my ears which of course is very subjective and affected by personal preferences.

I can hear a very slight change in sound when the laptop is running off the mains but it's very difficult for me to describe it. I connected and disconnected the PS multiple times while the music was playing and listened for any change in sound. The best I can describe it as the music sounds very slightly congested and unclear when I connect the mains power.

 

[DNICE1]

Those of you that follow the ODAC may have learned to despise RMAA, but if used for direct comparison rather than absolute measurements, I don't think you can fault it:

If possible, could you run the same tests on an ODAC with and without the external PS and post the results? I think that many here including myself will be interested in your findings.