nuforce icon uDAC-2 in the nude

Hard to figure out which is the right forum, here or computer audio. Anyhow, if anyone was wondering (as I was) what the insides of the little beastie look like, wonder no longer:

Revealed: a pretty dense layout, most SMT, with a daughterboard for the volume control and headphone section. At least five ICs, plus voltage regulators. A number of passives on the reverse side of the boards, too. Quite a feat of engineering, packing it all such a tiny volume. I'm pretty pleased with my purchase.

I've noticed Nuforce taking some flak in these forums for not disclosing which chips it uses. fwiw the ICs in the uDAC-2 have what appear to be custom markings with "nu" (for nuforce?) printed on them, a date code, and some other alphanumerics which turns up squat in Google.

That get's a fat "no comment" from me. At this price point they can do whatever they like: I have very low expectations regarding the actual cost of the chips and and I won't complain if the decide to protect their I.P. like this. Good circuit design matters as much or more anyway.

some other misc notes:

A single length of red wire as a jumper suggests some last minute revision, or an unsolvable routing issue.

The two large orange capacitors are curious. They are 2.2uF 50V polar electrolytics marked "L.L". All the other caps are SMT types, and rated for much lower voltage, 16V or less. Why go out of your way to use these big and bulky radial caps with such a low capacitance value? Beats me. A pair of 10uF 16V SMT caps sit nearby.

Yeah, a number of people were unhappy with that. I've had no problems with my uDAC-2 with 16ohm 104dB Denon AH-C700's.

Quote:

Originally Posted by techenvy 

hey thanks we appreciate this.  any idea what dac cip she uses?

 

thanks

I'd be willing to bet money it's a rebadged ESS ES9022.

http://www.esstech.com/PDF/ES9022_PF_090731.pdf

(16SOP package: check, 2Vrms output: check, no DC blocking capacitor: check, minimal components: check, decent specs: check, single supply 3.3V DC operating voltage: check.)

I feel I'm on a roll. Let's take a guess at the headphone amp: most likely the MAXIM MAX4411 or possibly the MAX4409. 

http://datasheets.maxim-ic.com/en/ds/MAX4409.pdf

http://datasheets.maxim-ic.com/en/ds/MAX4411-MAX4411B.pdf

DC coupled output: check, 80 mWpc at 16 ohm: check. 20 pin 4x4mm package, check. 3.3 VDC single supply operating voltage: check.

re: distortion at high volume. "cranking it" can sometimes harden the sound, depending on program material. Typical for it's class (portable audio) and pretty much unavoidable given the low supply voltages (+3.3V, -3.3V from charge pump circuit).

To clarify, the uDAC-2 has a different pot from the original, and does not have any problems with channel imbalance, etc.

FWIW the uDAC-2 has an improved headphone amp.

Setting the volume level to 3/4 is likely to cause clipping in either product, unless the original recording is of an unusually low level. No reason to think the unit is defective.

Assume program material peaks are -6 dB, so 1 Vrms of the 2 Vrms line output from the DAC. Assume the headphone amp has a gain of 6dB (MAX4411B). If the volume exceeds -6 dB (3/4 turn), the output signal will exceed 1 Vrms.  The clipping point for the amp with 16 ohm headphones, 80 mW, is 1.1 Vrms.

80 mW is also in excess of 140 dB for most headphones. Keep it safe out there kids.

Quote:

Originally Posted by tranhieu 

Thanks, perhaps I got a defective unit, but a friend of mine also experiences the same problem. It's a great little unit with a nasty pot though.