[Yikes]

The RCA outs are a Line Level output (Approximately 2 Volts P-P) that are designed to drive a Higher Input Impedance Line Level Input (Usually 10,000 to 100,000 Ohms). Whereas the Headphone Jack Output is designed to drive a Headphone type load that typically varies from 16 to 600 Ohms. Also the input Impedance of an amp typically doesn't change much across the audio band, but the Impedance presented by most Headphones does tend to vary over the audio bandwidth.
 
So it's no surprise that the two outputs perform differently with different loads. They are designed for a specific use, if you use them outside of their intended application they won't perform optimally.

 

[lazpete]

Strange episode today. I noticed I wasn't getting a signal to my right speaker and swapped cables at the uDAC-2 RCA outs to confirm it was a DAC issue. While swapping cables I found the uDAC-2 to be really hot. I unplugged the USB cable from the back, waited a couple seconds, and after plugging it back in the uDAC is working normally and the temperature is back down to normal. What could cause it to get so hot?

Same thing has happened to me too, on both udac2's.

 

[jasonl]

Quote:

I just got feedback from Nuforce help desk, and they want me to send the UDAC2 back, for a replacement unit, so apperantly, they found something thats not right with the "tone" units.
 
Lasse

No we haven't found anything that's why we need to get your unit back for testing. May be it could be a few problem units due to parts problem as some have speculated. At this point we still don't have any "tone" units back at our lab or factory.

 

[jasonl]

 
Quote:

Same thing has happened to me too, on both udac2's

This temporary problem happened to uDAC too. Turn it off while you are swapping cables. Treat it like a piece of high-end audio

.
Unplug the USB cable power reset it and it will be fine.

 

[replytoken]

Quote:

No we haven't found anything that's why we need to get your unit back for testing. May be it could be a few problem units due to parts problem as some have speculated. At this point we still don't have any "tone" units back at our lab or factory.

 
Mine is now on its way.  You should have it by Wednesday.  I look forward to your test results.
 
Thanks,
 
--Ken

 

 

[BournePerfect]

Jason:
 
     Any word on why some of us are having 'dud' usb cables with the uDac-2? We're getting 'current exceeded' errors and the like, and cannot use the cable. I couldn't even START my computer until I unplugged this cable-my PC just kept shutting itself down, for safety reasons I assume.
 
-Daniel

 

[jasonl]

Quote:

Jason:
 
     Any word on why some of us are having 'dud' usb cables with the uDac-2? We're getting 'current exceeded' errors and the like, and cannot use the cable. I couldn't even START my computer until I unplugged this cable-my PC just kept shutting itself down, for safety reasons I assume.
 
-Daniel
 

 
Are you referring to uDAC2-HP?  A whole batch of 200 uDAC-2HP package has bad cables (these are the transparent cable and factory didn't even bother to test since the supplier has been very reliable but they made a careless mistake this time).  But with Nuforce, you could be lucky when you get a problem

.  We are contacting all the uDAC2-HP customers and will send them a 0.5m Impulse USB Cable ($19.95) free of charge as our apology and compensation for the defective USB cable.
The best way to handle a problem is to contact our support. 

 

[WarriorAnt]

Quote:

Wow - great support! 
 
Has anyone tried plugging their phones into the RCA outs yet?
 
Completely silent - no hiss whatsoever!

Are you speaking of the RCA oust on the back?  How do you connect your headphones there?
 

 

[jasonl]

"tone" problem update

 
I suspect a fair amount of the reported problems are due to noisy, bad quality or under powered USB hub.  Note that even when you plug the uDAC-2 to your laptop directly, internally it has USB hub. 
There might well be defective uDAC-2 out there that cause high pitch and loud "tone" problem, but so far we don't have any units returned to us.
The one and only tone problem we have received in the USA (and hundreds were sold here) is posted on our help desk and has been resolved:
 
"There is a quite audible high frequency tone in the background on my uDAC 2 (and I've seen other people with the same problem in various forum threads). I've tried with two different computers and it's the same on both computers. My guess would be that the problem lies in the uDAC 2 and not the computers. The tone appears when the uDAC 2 is turned on and remains constant in volume no matter how high the volume is turned up on the unit itself. I've tried with two different headphones, 32 ohm Beyerdynamic DT770 and 16 ohm Denon AH-C751. The tone is a lot louder on the 16 ohm ear plugs, to the point that it's easily audible while playing music on low volume."
 
The customer later replied:
"Hi, I've bought a USB hub (actually to try to rule out psu/mobo in the other problem I mentioned), and when connected through the USB hub, even if it's the same port, there is no tone (and no popping sounds either). I'm not quite sure why this is, however."
 
When using non-powered USB hubs, the power is drawn from the USB controller. The amount of power that can be drawn from the controller is rather limited.
Non powered USB hubs are nice for mobile use or when you just need a few small devices on the USB bus, but they have a downside. Although modern software (like Windows XP) detects when you are "overloading" your USB bus, some hardware can't take it and becomes unstable. Although this isn't common, it's wise to use powered USB hubs whenever you can (unless you have good reasons not to, such as for mobile use).
uDAC-2 works in most laptops and desktop computers. But in a few cases, due to the design of USB ports on your computer, or the usage, you should use a powered USB hub (and get a good quality one).
 
If you are from Sweden, we are waiting for the "tone" units. If you are from any other countries, please contact us. At this point, we have no other report of tone problem from anywhere else (other than the one problem from USA as reported above but resolved with a USB hub).  Again, it is very important that you contact Nuforce support directly. The more feedback we have, the better we are at addressing customer's issues. Posting your problem here is fine, but won't help our support staff unless I come across it and report to them.

 

[mr-teatime]

well, as one could read a couple of posts back - when connecting to an unpowered usb hub or a very long usb cable (resistance) the "tone" is not audible anymore - couple of independent tests from customers let to the same result. the customer you are quoting isn't mentioning powering his hub ...
anyway - curious to hear feedback from ken's device. i haven't any feedback from the helpdesk yet - i guess they need a coule of days to plough through the requests ...
and again - owning a relatively high quality macbook pro i'm not willing to attach some funny stuff to it to attach the udac2 to it, since the udac2 was designed to be an elegant solution and no diy whatsoever for just this kind of set-up ...
luckily the sound quality is still outweights this quirks and i'm still a kind of lucky customer ...
greetings from london ...

 

[replytoken]

Thank you for the update, Jason.  As you have not questioned our hearing the tone, I am open to your theory of bad usb hubs.  What might be a bit helpful to us, though, is to let us know the machines that you use to test the uDACs.  I do not doubt that many computer companies use cheap usb hubs, but it would be nice to know who might be problem free.  I am sorry that I did not do more systematic testing before sending my unit back to you, but I am hopeful that you will be able to reproduce the noise, even if it is exclusively from an underpowered USB hub.  I look forward to your analysis, and I miss having my DAC.  I had hoped to bring it on an upcoming trip to use with my laptop or netbook and my ETY's, but that is where this problem began in the first place. 

 
One follow-up question.  If a good, powered hub is the solution, is there any loss of sound quality from the additional cables, hub and power supply being added between the PC and the DAC?
 
--Ken

 

[BournePerfect]

Jason:
    Thanks for the quick response! Yes mine is the uDac-2 HP that came with the short clear usb cable. I bought it through Amazon, but the seller was Audio Advisor. How do I go about getting the replacement cable?
 
-Daniel

 

[lazpete]

Jason, I really appreciate you being here, answering our questions.
I spoke to my dealer, and they listened to all 6 units that's been returned, and all of them made the noise. The SE distributor did the same, with the same result.
The reason I'm hesitating in sending my second unit back, is the fact that even after three weeks since shipping my Icon mobile back, I still ha vent heard anything from you guys. And buying gear, that needs weeks of shipment time, is not what I like, even though I really thank you for your efforts.
So, if you find something with the units that should be heading your way from the SE dist, I feel it's lot more secure to trade my unit at the dealer, than sending it overseas.
 
And, as a comment to the USB hub thing, I tried two different hubs (HP USB Dock, Kingston , Target 7 port USB hub), and a non mains connected battery charger, the tone is there.
If I connect the UDAC2, via RCA to my Little Dot 1+, or my M-audio monitors, and try listening for the tone, it is not there. This is no matter what USB connection is used.
 
So, the coward in me will wait and see whats happening, and if it becomes necessary, I will for ship my UDAC2 back, but a prefer using my local dealer, if possible.
 
Lasse
 
Quote:

No we haven't found anything that's why we need to get your unit back for testing. May be it could be a few problem units due to parts problem as some have speculated. At this point we still don't have any "tone" units back at our lab or factory.

 

[tinseljim]

Quote:

Are you speaking of the RCA oust on the back?  How do you connect your headphones there?
 

I posted a picture a while back...plug an RCA to hp jack (male) into a female-female hp jack and voila. of course you could make/find a RCA to female hp jack adaptor (but these are harder to find). The hiss is completely gone with my fairly sensitive IEMs and I would imagine the tone problem will disappear as well (i don't have this problem so can't say). Could at least one person try this! 
 
 
 

 

[JackG]

Quote:

 
This temporary problem happened to uDAC too. Turn it off while you are swapping cables. Treat it like a piece of high-end audio

.
Unplug the USB cable power reset it and it will be fine.

  Thanks Jason. Mine is fine after the reset I was just a little concerned about the amount of heat produced. I only swapped cables after it happened.