extremely bad noise with O2+Odac combo connected to hifi

AuFX

Member
This is 'Digital' version of the 02+odac combo from Head n' Hifi, its only input is USB.
Im pretty sure the noise is coming from the USB input on the combo which is connected to my PC. If I unplug the power adapter from the combo and just have it connected with USB the noise is exactly the same, I believe the ODAC is running solely on USB power while the power input is just for the O2 amp... this eliminates the headphone amp as the problem.... which is odd because I didnt expect there to be any issues using the ODAC with a hifi.

Headphones are completely unaffected, no noise at all... only happens with the hifi.

its digital noise, like really inconsistent sounding noise; changes in tone constantly, a not smooth hum or buzz and cuts out now and again for a second, its definitely some sort of data stream thats getting amplified. I can hear it through my hifi on all channels and even when the volume is at zero.

I have all the devices in the chain connected to power strip in one wall socket so it dont think its a grounding issue...

do you guys have any ideas what the problem might be?

EDIT: Im not sure the cause of this problem but I think I may have a simple potential fix... slicing open the USB cable and connecting an external 5V supply to the USBs power wires for the ODAC.... well this would be the easiest way if it will work but IM sure there are better but more complicated/expensive ways to fix this.
 
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If your PC is a laptop see if running it on battery helps. Powering from an external 5V supply as you describe isn't a very good idea and may not work at all. A USB isolator between your PC and the DAC might help, like:

http://hifimediy.com/high-speed-usb-isolator-480Mbps

or

http://ifi-audio.com/portfolio-view/accessory-idefender3-0/

Also see this discussion:

http://audiokarma.org/forums/index.php?threads/high-pitch-whine-from-usb-on-docked-laptop.749059/
Its a desktop (should have mentioned this important detail sorry, 'PC' and 'Desktop' and synonmous in my head at this point)

Ive ordered the USB isolator and hopefully it will fix my issue.. if not I will have to switch over to an optical SPDIF supported DAC.

Thanks for the advice
 
Ive ordered the USB isolator and hopefully it will fix my issue..

Which one did you order? Please report if it helps and if any issues using it, I'm suffering from milder but similar issues as well and wanted to try the isolator.
 
Which one did you order? Please report if it helps and if any issues using it, I'm suffering from milder but similar issues as well and wanted to try the isolator.
it was Hifime's adum4160 based isolator, the cheaper one from them, It was between that and the slightly more expensive 'Jitterbug'... I read about hifime products having very good price to performance ratios and the ODAC tops out at 24/96000Hz and draws a mere 50mA so its limitations didnt apply to me.

I will report back to you... but to be honest Im having my doubts about it being a 100% perfect isolator. Im looking for a crystal clean signal , as digital should be, even the faintest noise would ruin my listening experience.
 
It should work, my concern is it may affect sound quality. Some better DACs have built in galvanic isolation, iirc Centrance was bragging about their DACmini CX being fully isolated, iCron USB over Ethernet extenders would also fully isolate as would Intona USB isolator, so there are other options besides optical but the price goes up and you'd be better off spending your money on an isolated DAC instead.
 
Also as far as Jitterbug, I don't think it provides any isolation at all. IDefender from IFI should be good however. Their original USB iPurifier provided isolation too if memory serves.
 
Also as far as Jitterbug, I don't think it provides any isolation at all. IDefender from IFI should be good however. Their original USB iPurifier provided isolation too if memory serves.
So after some use all seems good with the isolator, its does its job perfectly as you predicted but I have really no way to judge if SQ is being affected, no obvious digital glitches or hiccups but you never know, they could be occuring at extremely high frequencies and blending in with the music. The SQ is noticeably more sibliant which im pretty sure is due to the huge increase precision with ODAC, I think the ODAC's transparency is not really as good a thing as I thought, especially with this HiFi. I cant understand why technically less accurate but far more expensive DACs would be used, its about sounding good... not sounding true
 
While there were some reports about ODAC being somewhat harsh in the treble the sibilance may well be introduced by the isolator. I've just impulse purchased a USB iPurifier but after reading the specs after the fact it turns out it doesn't provide full isolation, it was the SPDIF variant that had it, oh well it does have some sort of filtering I'll see how it goes. Someone on headfi reported a Furman power conditioner helped with the buzzing, would be interesting to try as at least in my case it seems to be related to both the computer and the amp being grounded, it might be a better solution than an isolator if it actually helps as there would be no need for an additional component before the DAC that can affect the SQ.
 
While there were some reports about ODAC being somewhat harsh in the treble the sibilance may well be introduced by the isolator. I've just impulse purchased a USB iPurifier but after reading the specs after the fact it turns out it doesn't provide full isolation, it was the SPDIF variant that had it, oh well it does have some sort of filtering I'll see how it goes. Someone on headfi reported a Furman power conditioner helped with the buzzing, would be interesting to try as at least in my case it seems to be related to both the computer and the amp being grounded, it might be a better solution than an isolator if it actually helps as there would be no need for an additional component before the DAC that can affect the SQ.
You should understand Im extremely sensitive to sibliance, im 98% sure its the ODAC now. I was also using a 3rd Gen Ipod Nano as a source before the ODAC and Ive recently discovered that it sounds good except for it absolutely butchers the highs, possibly a design choice but their is significant dB drop above about 11k . Additionally I was using a gimmicky 'bi-amp' setup with 2 integrated amps for these tests because I had the use of a second amp for a few days and was curious what it would be like, the amp was a Pionner A30 and it was driving the high frequencies, I had found it very thin on its own especially in the high end. my usual amp is a Pioneer A400x, the other amp is gone and back to using this now and I realised the A30 had a tad better seperation but everythign else about it I hated, all it provided to the 'Bi-amping' was more watts. the ODAC and A400X sound abosolutely gorgeous together, the warm creaminess of the A400 and crisp sound of the ODAC compliment each other nicely.
 
Another note, perhaps you're doing this already, when/if playing from PC/Windows you need to bypass Windows mixer and ensure there is NO resampling in the audio path prior to the DAC to ensure best SQ, Windows mixer + resampling is a recipe for sibilance from my experience. If you don't know what I mean lookup ASIO and/or WASAPI.
 
Another note on the subject, came across this device. Someone on head-fi mentioned it works great for audio, probably best if used on Gigabit network. Reasonable price, much better than iCron extenders and should work across existing hubs/switches if one needs to send signal to another room. Apparently it also provides galvanic isolation, likely due to impulse transformers on the device. I imaging you could also make it work over a short direct CAT5r/6 cable provided your PC has a free Ethernet port. You could also power the box from a linear PSU to further reduce noise on the USB.

https://www.amazon.com/Silex-DS-510-Device-Server-Ports/dp/B00U9UDSH8
 
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