I am happy with the Audiotrak DR.DAC2 DX. My headphones are AKG K701s.
Hardware and Software
I am using the DR.DAC2 DX in Linux Ubuntu 10.04 64 bit on an HP Elitebook 8540w via USB. I have trouble with kernel versions v2.6.32-22,23,24,25 (the system freezes when plugging in the DR.DAC2 DX) but downgrading to 2.6.32-21 solved that. I also tried it briefly in Windows 7 on the same machine and in Debian Lenny, kernel 2.6.26-22lenny1, on an old Thinkpad T43p, which both worked fine.
So far I had no success with the USB3 ports in Ubuntu - I haven't really tried for long and in Windows 7 the DR.DAC2 DX works also on the USB3 ports.
The following combinations of input and output all work:
- USB in -> headphone out
- USB in -> line out (confirming what Pricklely Peete and SaiSai said)
- line in -> headphone out
- line in -> line out
I do not have an S/PDIF source available. Note that I only checked that the line out works in principle by connecting it to my headphones - I don't have active speakers yet.
I was able to send 44.1 kHz, 48 kHz, and 96 kHz files via USB and the corresponding LED lighted up as expected. Via USB 88.2 kHz, 176.4 kHz, and 192 kHz do not work. (That's all as stated in the user manual.)
Listening
A main reason for buying a USB dac/amp was that the headphone out of the HP Elitebook 8540w did not deliver enough power for the K701
on low volume passages of some classical recordings. (The 92HD75B in my laptop is rated between 31 and 40 mW at 32 Ohm.) Specifically, when I wanted to listen in closely to the first part of Bolero on MFSL UDSACD 4002 I could not turn up the volume up as loud as I wanted on the laptop headphone out. The DR.DAC2 DX solved that problem. I use the low gain output.
When connecting the DR.DAC2 DX via a USB hub rather than directly to the laptop then I hear some crackling noises. I checked 2 USB hubs, 2 cables, all 3 USB2 ports, operation with and without power to the USB hub and the laptop, and Ubuntu and Windows: same result. Moreover, the amount of noise seems to depend on the laptop USB port to which the USB hub is connected: via one port its somewhat listenable, while via the worst port is completely unlistenable. On the other hand the crackling did not occur when connecting the DR.DAC2 DX via USB hub to the Thinkpad T43p. Can anyone shed some light on whether this is solely a property of the computer side or are there some USB implementations on the DAC side that are less susceptible to these problems that others?
Seller and Shipping
Buying from gyrocom was almost perfect.
I had to ask for a tracking number by email rather than being it sent automatically; that is the only thing I would improve.
Communication was always very quick.
I ordered the item on a Sunday afternoon, it was shipped via EMS Monday morning, and I picked it up at the courier's depot Wednesday one week later. EMS turned out to be TNT in my case. Somewhat contrary to the information on the seller's ebay webpage I did not have to pay any additional fee for shipping to Italy. I had clarified that via email in advance. 2 or 3 days of the overall shipping time are probably owed to importing this to Italy. I guess the following are pretty standard for Italy: the courier service contacted me via phone/email to provide them (via fax) with my Italian tax code, a copy of the ebay offer, and a copy of the paypal receipt. Once I had sent that to them the item was forwarded from the "entry point" in Italy (Milano) to the courier's depot close to my place. In addition to the ebay price of about 300 EUR I had to pay about 90 EUR import taxes, tariffs, and handling fee. (I've seen a reduced price by gyrocom on ebay recently.)
Those are my impressions after about 3 weeks. Thanks to everyone who answered my questions before, in particular Scrivs, SaiSai, and Pricklely Peete.
HTH