Specs:

• CM6631 USB chip, supporting 192K/24bit
• WM8740 DAC
• NE5532 opamps
• TPA6120 headphone amp
• ALPS potentiometer
• upc1237 headphone protection circuit

Total $89

http://www.ebay.com/sch/m.html?_odkw=192K&item=200883314472&pt=US_Home_Audio_Amplifiers_Preamps&_osacat=0&hash=item2ec5941f28&_ssn=pbuying.usa&_trksid=p2046732.m570.l1313&_nkw=192K+usb+amplifier&_sacat=0

@kronstadt

It is high quality headphone amps, ones that you use in studio with your headphones :-)

In same time works as DAC to your studio monitors,

Check topic title.

And you can use them in home just as headphone amp. Period.

I used to use a Presonus Firebox as a headphone amp DAC and of course a recording interface.

Yes, of course. But many people really do not need all the complexity. Plus usually DACs, opamps, power design, on complex devices are worse.

I've tested a bunch of these, for the high end I like the Mytek designs. But for the low end, small, beautifully made, with a clear, detailed sound I like this box. More than good enough for professional work:

http://www.ebay.com/itm/HIFI-NEW-Version-DAC-Decoder-TE7022-CS4398-24Bit-96Khz-USB-RCA-headphone-output-/140751305382?pt=US_Home_Audio_Amplifiers_Preamps&hash=item20c56e7aa6

There's a bunch of factors to consider in the DAC design, specifically whether it is really 24 bit or not--a lot of these DACs knock down the SR to 16 bit. Even some of the high end boxes fib about the bits.

But without going into the technical aspects, this is a great box for $50. Next step up are some of the musiland designs, they are very good.

I would stay away from boxes using the NEC 5532 chip, for long and complicated reasons. It can sound OK, but it often does not. This chip is the one most often replaced in an op amp upgrade. The CM6631chip is a pretty big seller in China, but as it is relatively new you may not have full driver support, so consider that. A lot of us use the Ploytec USB driver which gives low latency true ASIO for audio, other solutions, like the Musiland, use their own proprietary drivers. The box I linked to uses a OPA2132 op amps.

I used to make these with op amp sockets, so you could pop them out and try different ones, but there are now good ones available on line and I was never the best solderer.

If you want something in between the low end and the high end (and the $50 box is what I listen on most of the time), the mid level musilands are almost indistinguishable from the really expensive stuff, like this special dragon edition http://www.ebay.com/itm/2012-Musiland-Monitor-02-US-Dragon-USB-Sound-Card-Amplifier-DAC-/110937050590?_trksid=p3284.m263&_trkparms=algo%3DSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D21%26pmod%3D320978911528%26ps%3D54

And if you want the absolute state of the art, discrete electronics, this guy makes some very good boxes that have an isolated headphone circuit, with high gain throughout, all audiophile components http://www.audio-gd.com/Pro/Headphoneamp/Sparrow/SparrowEN.htm

Audio-gd stuff is mostly socketed, so you can swap out op amps and stuff. Like I said, though, the weiliang design is 24 bit, good converter and op amps, sounds good and is $50. Plus it is powered by USB.

Good stuff.

@kronstadt A lot of ppl who work with audio want an external soundcard, which means no interference from the computer, to monitor and master the audio for CD, film, etc. It should be external, high quality, preferably neutral and detailed, without being fatiguing. Ideally, it should be 24 bit (or higher) and have ASIO driver capability. Some people like exotic sample rates, like 192 or 384, as well. ASIO allows you to bypass the internal crap in your computer so if something goes wrong, you can figure out what it is. You don't want for example the computer's mixer to be mixing away in the background. It can also give you low latency for when you are listening back to recorded sound.

Other ppl want a high quality DAC for their home stereo, or even for their TV (yes, I have one hooked up to my TV to feed a pair of speakers). Some of these have a high current speaker amp built in, so you don't need an amplifier. Some ppl just want a $50 box that makes their music sound better and could care less about the rest of it.

@DrDave thanks for the detailed explanation. Now it makes sense. I'm guessing sound-editors and sound-mixers have something like this as a part of their editing computer.