REVIEW (in progress) - Nuforce HDP 24/96 USB-Optical 24/192 Coax DAC Preamp and Headphone Amp - Page 102

http://www.nuforce.com/index.php?option=com_k2&view=item&id=32:linear-power-supply&Itemid=204

Was messing around with my HDP and stumbled upon something cool/wierd. Here's the experiment:

 

http://mdf1.tripod.com/test-tones.zip

 

Play the 1000Hz sound on loop and then change the volume, do you guys get any noise? My volume pot usually doesn't generate much noise, but for some reason, playing 1000Hz pure tones causes the pot to generate an incredible amount of noise

 

Can anybody with a degree provide an easy to understand explaination for this phenomenon?

Edited by vysis - 11/13/12 at 11:06am

My volume pot likes to make noise in large volume swings, like if I suddenly turned it from 11 o clock to say 2 o clock.  I've heard it fairly common in the unit and not a reason for concern

edit: nevermind

Edited by Armaegis - 1/14/13 at 9:26am

Sorry for the ridiculously old necro.

 

Got my HDP serviced after it was making noise, but instead of repairing it, they sent a new unit. This new unit is rather wimpy and cannot power my headphones much compared to my old unit. It uses the 15V 24W AC adapter. Would I get more power if I used a Toshiba PA2450U laptop AC adapter, which is rated at 15V 45W? Would a 90W (6 amp) AC adapter damage the unit?

Edited by colgatetotal - 2/6/13 at 10:25pm

If youre going to upgrade the power supply, build a Sigma 11.

Or get the actual LPS power supply from Nuforce... but the wattage shouldn't make that much of a difference. Something rated for higher wattage will make no difference; the HDP will only draw what it needs, and that would only be a couple watts at most. If you were driving something like the Icon amp which powers speakers, then it'd be a different story.

 

But in any event, if the new unit is not performing well, maybe contact customer service first? There shouldn't be any reason why the two are different. What headphones are you using?

Yea what you'd want is a linear power supply as that would be about the only power upgrade that would yield any audible difference. Maybe you got swapped with a defective unit. I'd call NuForce.

The HDP comes with a 24W PSU as standard issue. Earlier in this thread it was stated that NuForce had offered a 42W PSU upgrade which did provide a bit more power. That is why I'm wondering if getting a Toshiba 45W laptop PSU would work. Unfortunately, I don't know whether my old unit used the 24W PSU or the 42W PSU. By the way, I paid $100 to have it serviced along with another $25 in shipping to send my old unit back. If this new unit is indeed defective, I'd want them to foot the entire bill.

 

The NuForce Linear PSU is 60W, but I can't justify paying more for the PSU than for the HDP itself. That is bordering on silly.

 

Oh, and the headphone? A Grado SR225i with ReplayGain (89dB), and it's not loud enough at 2 o'clock. At 3 o'clock it's OK but at that point the unit starts hissing. My old unit could reach the same volume at 11 o'clock.

Edited by colgatetotal - 2/7/13 at 3:41pm

Sounds like something is definitely wrong with your unit. Shoot them an email and ask for a prepaid fedex return label.

 

As for spending money on power supplies... well, that's the world of diminishing returns for you. I have the HDP and the fully upgraded LPS. I use the LPS bridge to feed optical to the HDP, which then outputs to my Icon2 (also powered by the LPS) which powers my HE-6. It's a nice little triple stack going. 

 

The LPS does give an improvement, but it's a very small one. In my case, it improves on three areas in my system so that makes it much more worthwhile. 

I got a response from NuForce:

 

If there is no distortion, noise, etc., then this behavior is within normal limits.  All volume controls vary in their range a bit from one to the next.  If you are NOT able to turn the unit up to sufficient volumes, then there might be something wrong.  Otherwise, the difference you note is just the result of normal variations from one unit to the next.  We hope this helps.

 

What a disheartening reply. I don't have any grounds to send it back because the unit sounds OK up to 3 o'clock. (Other people have reported hissing from 3-5 o'clock, so this is "normal") It's just that it's not very loud. Also, I question the production variance in a mass-produced unit such as the HDP.

 

I got the Toshiba PA2450U PSU today, but the tip is larger than the HDP's. I'll get the tip spliced later in the week and tell you how that turns out. I will also put up a video to prove that I'm using direct optical out and that it's not my system at fault.

Edited by colgatetotal - 2/9/13 at 10:22am

Wow that's pretty lame. I haven't had any issues like this with my HDP and still consider it a great bang for buck dac and amp. You could try pressing the issue with them and flat out state you'd like a replacement.

And specifically say that there is no way such a large variance in gain is attributed to "normal variations". Do you know anyone nearby who has an HDP to confirm the difference?

Pardon me if this has been asked before, but since the HDP doesn't "support" 24/88.2 via USB, does this mean if I try to play a track at that sampling rate there will simply be no audio output?  Or will the device "downsample" if that's even possible.