usb dac for hi-end system

And to add what to Jeff said, it doesn't make a difference if you use firewire or USB because all you are doing is sending bits from one place to another. The better implementations using either interface do not try to recover clocking from the input data stream. So, in this case if the sound is really different (vs imagined) and all other things being equal, the bits would have to be changed to account for the difference in sound. This is easy to prove right or wrong. Just copy files between a USB drive and something else with data integrity checks. How many times will the target data not match the source data?

And, most likely many "professional" studios/people use firewire because it was the interface of choice on MACs where just about all the "good" music software started and still exists. And it does have some advantages over USB, especially for multiple devices which not the setup most people use to take PCM from a disk drive and send it to a DAC.

I'm at a loss with your Scarlatti why you would not just use the matching dCS USB interface?

http://www.dcsltd.co.uk/product/scarlatti-upsampler

Surely this is matched and surely dCS would not release anything inferior? Thoughts?

I use the Paganini equivalent set up and as far as I can tell, with J River Media Center /Wasapi exclusive / ASUS EB1501 USB / Paganini USB interface, the sound is every bit as good as the Paganini transport via AES EBU. Adding room correction (Audiolense), it is clearly better than the transport.

I've not compared other DACs but have reports from two reviewers who have, that you the dCS gear is definitely in a different league to the cheaper DACs.

Look forward to hearing of your experiences.

When asynchronous mode is used, Firewire and USB are identical in performance (in theory), assuming that the USB interface is well implemented. This means good design, layout and parts choices.

However, the implementation is where the differences happen, and it's due to the fact that most of these designers are not digital designers with a a lot of high-speed experience, even at the larger, older companies.

All it takes is for the designer to throw the schematic over the wall to the layout guy. This will usually ruin the design. If the designer does not do the board layout manually himself, the design will undoubtedly be compromised. He/she must be both a good circuit designer and layout designer to achieve a stellar result. There are literally thousands of critical design decisions along the way in both the circuit and board design.

Steve N.
Empirical Audio

I agree with the posters who have recommended that you consider a USB to S/PDIF converter, such as this one. You have such an amazing digital front end already. Adding a converter to it would be a very economical way of getting your feet wet with computer based audio.

definetly I agree with you on dcs gear but I just wanted to check wheter there is some other dscs or converters to be tried.
and actually ı have tried last weekend direct from mac mini via minijack to toslink adpater to dcs dac, result was really satisfying.