uDac 2 - High frequency noise is audible on "quiet" input

Ingvarr · « **on:** 17 Sep 2010, 03:55 pm »

Just got my new uDac 2.
I must say it performs music playback very well, however I instantly perceived very noticeable continuous high-frequency noise (10+ khz I think). It is noticeable when not playing anything or during quiet intervals in the music. It's not the DAC noise since I can distinguish actual DAC "white noise" by turning volume knob. This high frequency noise does not seem to be affected by volume knob.

I was quite baffled by this because even my laptop integrated headphones jack performs better in this respect - I hear only DAC noise there.

The headphones I've tried with is Etymotic hf2

Any advice on this? Maybe I've got a defective unit somehow or is this something inherent to uDac?

rustydoglim · « **Reply #1 on:** 17 Sep 2010, 10:47 pm »

We have heard about this problem. It is likely due to the computer noise coming through the USB cable.
Try:
1) use a better USB cable
or
2) external USB hub

Ingvarr · « **Reply #2 on:** 18 Sep 2010, 12:10 am »

Umm, not sure what is "better" cable, since I've used one that came with uDac 2 in the box.
I've tried the different spare cable I had anyway, and no change.

I've tried with powered USB hub from Targus - no change.
I even tried disconnecting the hub from PC. I heard brief change in noise "tone" when I unpluged hub from PC, but then noise was restored to exactly same "tone" and intensity like it always was.

So I doubt that's PC is the source of this

rustydoglim · « **Reply #3 on:** 20 Sep 2010, 12:12 am »

It is almost impossible to remotely diagnose this type of problem. It could just be your environment, or you might have very sensitive hearing. A defective uDAC2 is unlikely since these products are mass produced and it is functioning. Try with other laptop or PC and if the noise still persist, contact our support and send it back for a test (if it is defective, we can send you a new uDAC2) and refund (if we can't detect it, there is nothing we can do).

Ingvarr · « **Reply #4 on:** 20 Sep 2010, 06:41 am »

Will do. Before that I will wait for new Sennheiser HD595 to arrive and test on this too, maybe uDac2 does not like Etys hf2 somehow.

I have usual hearing, but with isolating canalphones like hf2 you can hear the slightest signal noise if its here.

However the major point is that there is no such noise at all on integrated sound card (or even my mp3 phone player), and I was disappointed that 100+ buck product can not perform at least no worse than that.

Ingvarr · « **Reply #5 on:** 22 Sep 2010, 04:19 pm »

Update: just did a test on Sennheiser HD595 and on completely different PC at work.
Noise still unchanged on other PC - instantly kicks in when knob clicked to "on" and stays at same level.

Noise is quite less audible on open headphones like HD595, but this is only mainly because outside noise is masking it - in the quiet room you can definitely hear that it's still there (especially the difference when volume switch is clicked off/on).

Creating a support ticket...

nuforce-casey · « **Reply #6 on:** 22 Sep 2010, 08:47 pm »

Quote from: Ingvarr on 18 Sep 2010, 12:10 am

Umm, not sure what is "better" cable, since I've used one that came with uDac 2 in the box.
I've tried the different spare cable I had anyway, and no change.

I've tried with powered USB hub from Targus - no change.
I even tried disconnecting the hub from PC. I heard brief change in noise "tone" when I unpluged hub from PC, but then noise was restored to exactly same "tone" and intensity like it always was.

So I doubt that's PC is the source of this

Which PC/Notebook do you have?

TopofRoc · « **Reply #7 on:** 23 Sep 2010, 12:11 am »

You aren't alone Ingvarr. I'm having the same problem...

I received my uDac2 last friday and I was very pleased with the sound. I've got it connected to a Mac Mini via USB. The Mini also serves as a storage server, so it's on for several hours at a time (the uDac2 is on during this time too). When I went back to my system (after a couple of days) to listen to some music, the same high pitched whine you mentioned was present. I tried different cables (USB and interconnects) but the noise is still there. It isn't consistent however. I shut my mini down for a couple of days and the noise went away. But now it's back.

I'm opening a ticket for it now...

Ingvarr · « **Reply #8 on:** 23 Sep 2010, 06:42 am »

Quote from: nuforce-casey on 22 Sep 2010, 08:47 pm

Which PC/Notebook do you have?

I've tried with Thinkpad W701 (notebook), hub in Dell 2407WFP monitor, and powered 7-port hub from Targus. It does not matter, noise always the same and present even on hub not connectecd to PC - it just something uDac2 generates when supplied with power.

Quote from: TopofRoc on 23 Sep 2010, 12:11 am

You aren't alone Ingvarr. I'm having the same problem...

Now that's interesting. Defective batch or inherent quirk of uDac2 I wonder?

Awgy · « **Reply #9 on:** 24 Sep 2010, 08:01 am »

I just received my uDAC-2 today and have not heard the high frequency tone on my SRH840's, so it may be a bad batch.

There is a thread over on head-fi where about 4 people are having the same problem.

palhenf · « **Reply #10 on:** 29 Sep 2010, 08:54 am »

I'm experiencing the exact same problems as mentioned here. Using Shure ec4. Have also tried different cables and pcs without difference. Though I can't hear it using Koss Porta Pro. The sound is probably drowned in background noise or because the Porta Pros can't render high frequencies as good.

lazpete · « **Reply #11 on:** 7 Oct 2010, 09:35 am »

Im hearing the exact same thing. Tried it with my SHR840, on three different computers, and even a standalone, travel battery charger, without any connection to the normal power network. So, there is a fault in the UDAC2, no doubt.
As I have already sent my icon mini back for other issues, Im kinda losing faith now...

Lasse

mr-teatime · « **Reply #12 on:** 7 Oct 2010, 11:44 pm »

same here - very apparent with low impedance cans - almost not with higher impedance cans - makes it unusable with "small" headphones ...
various sources and cables tried ...

lazpete · « **Reply #13 on:** 8 Oct 2010, 07:12 am »

Strange thing is, that this morning, after the udac2 has not been connected at all, the high pitch noise is gone, only to return after the unit gets warm.
I'm exchanging mine today at the dealer here, will be back with news this afternoon.

lazpete · « **Reply #14 on:** 8 Oct 2010, 11:46 am »

I have now warmed the exchanged udac2 up for half an hour, and the high freq noise is very very much lower on this one. I will let it go completely warm, and we'll see what happens.

Lasse

lazpete · « **Reply #15 on:** 9 Oct 2010, 03:27 am »

So, the conclusion of this, is that there is still a high frequency tone present, but on my second udac2, its very much more subtle. The talk that its a design thing from Nuforce seem kinda strange, as the two variations of tones I have encountered, suggest two different designs.
So there is definetly a bad engineered batch thats out there.

Lasse

Ingvarr · « **Reply #16 on:** 9 Oct 2010, 08:10 am »

In my case nuForce told me that they will not be able to fix it, and I have returned my uDac2 for a full refund.

Lasse, even if tone is "subtle", this is still wrong for high-quality device. With proper design you should hear no parasitic noise at all, as long as volume knob is in low position (in high position you will start to hear white DAC noise).

lazpete · « **Reply #17 on:** 10 Oct 2010, 04:16 am »

The thing I find strange, is that there seem to be udacs without the "tone".
Well, I heard that Ljudmakarn in Stockholm sent back 6 pcs Friday, and that the agent i Sweden is well aware of the problem.

Ingvarr, I agree, there should not be any tones at all, and the noise will rise with the level of output, thats for sure.

serlu · « **Reply #18 on:** 11 Oct 2010, 02:52 pm »

Have just bought µDAC2 and first thing I noticed was "hissing" with volume turned low.

This was with Apple in-ear head phones. Well those have been mistreated and gone through the washer twice.

I tested with my Grados - could not hear any noise with them. But ambient sound may "kill" the noise.

Tested with Etymotic ER-6. Noise
Tested with Shure 310. Noise.

So I get audible noise from three out of three in-ear phones.

This is the same noise I get with some iPod models with a bad headphone "amp". Actually had to return a pair of Shures (highest end canalphones thay had at the time) due to that they were so sensitive that slightest noise in headphone out was perceptible.

Besides this noise - they are fantastic. Best sound I ever got out of my Etymotics. Much more dynamics from them.

serlu · « **Reply #19 on:** 11 Oct 2010, 03:03 pm »

After doing some more testing one thing I find quite confusing is that I still get sound with the volume knob turned way down "sitting on the click" so to speak.

Also turning the knob to increase the volume is not givin a smooth increase in volume. The first 2-3mm gives no change. next 0,5-1mm engages left canal, before the right canal starts to increase in volume.

And no - I do not have "Golden" ears. Normal hearing for my age.

But I do not find this acceptable for a "lower middle high-end" product.