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What USB ASIO you are referring to ? Where I can download and try?

Before you make conclusion of hi-def files, please note that that may be performance bottleneck due to PC noise, PC background program interruption, foobar setting and quality of M-Audio Transit. After you optimize your computer audio system, you may be able to hear a big difference. I can hear big difference between 24/96 and 16/44.1 files from Linn Records. I'm using Cplay + ASIO4ALL, Benchmark DAC1 PRE (USB connection). I have optimized the PC so that ASIO buffer can set to minimum 64 samples and it absolutely no click. I even stopped my windows desktop when I play music. I use notebook power by battery which is lower noise than desktop PC. I have also use the TOD2 USB cable to stop noise from PC entering my DAC. So don't give up. Try investigate more and you will have fun getting each performance bottleneck removed and hear what you expected with hi resolution music.

I fully understand that people who has product implemented Asyn USB will try convince that Asyn USB is one of the most important factor to get good audio performance. I won't be surprise Gordan said "... all the audio companies are flocking to the Asynchronous technology." Similarly, other vendor with 24/192 would say 24/192 on USB/Firewire is a must. Every manufacturer should rush to implement 24/192. If they are all correct, it is better buy EMU 0404 USB support Asyn USB and 24/192 sampling rate. And it is only around US$200 and have the 2 most important features for DAC. It is even worse. For Firewire DAC, they would say Firewire is the only true asyn technology with the DAC being the master of communication. USB technology only allow PC be the master. "Asyn USB", "24/192", "firewire" are not new but unfortunately becoming sales tools of audio engineers (a.k.a. sales engineers). It is like in the analog audio world, one may say balanced XLR connection is better than RCA and every manufacture should go and use XLR. But in reality. there are excellent and poor implementations of XLR and RCA. We choose the ability to deliver music, not the technology hype. It is annoying that vendors argue here. Especially when one ask question about a product and its competitor come to attack. I rather want to see vendors save their time arguing and spend time helping their customer to get best sound. Customers will tell which one is better.

For Benchmark DAC1 Pre, USB interface support up to 24/96. If you want 24/192, you need to use the SPDIF (coaxial) digital interface which support up to 24/192. What is your source? Can your source output 24/192 SPDIF format? Buy a source which can output 24/192 SPDIF (it can be a PC with profession sound card, a profession recording equipment or even a notebook plus a EMU0404 USB or M2Tech Hiface USB interface),and then you can use it with your DAC1 PRE with sampling rate 24/192. By they way, where you can buy 24/192 audio record? I found it very difficult to find 24/192 records available for consumer. If you try upsample 16.44.1 to 24/192 and then send to DAC for processing, you better think twice. I tried many different software upsampling, they are not improving overall sound quality. And 24/192 may not sound better than 24/96 as some DAC chip is under stress with 24/192 and actually producing higher jitter.

There are lots of discussion here regarding audiophile USB cable with better material and construct. I'm more interested in cable which pass digital audio signal but not noise from PC. Here is what I recently read and it makes more sense to me than yet another USB cable with better material & construct. http://www.tnt-audio.com/accessories/tod2_usb_lead_e.html

Just confused by reading various post regarding asyn usb implementation. I think it is implemented in some control feedback to adjust USB to send faster or slower to match with the DAC clock. But what that means is that the incoming data rate is constantly being adjusted and always slightly different from DAC clock. Is it being resampled? What would DAC do to handle this problem. I'm thinking of CD player, the CDP is constantly adjusting the CD spinning rate to have a constant data stream. This process may create a lot of jitter.<br /> <br /> Another question, if DAC clock is slower than the speed of player software. With Asyn USB, the USB transmission follow the DAC clock. So we have a player software keep sending data with its own speed, which is faster than the USB transmission rate. What the PC is going to do to handle it?<br /> <br /> I think if the player software also slave to the USB transmission speed, it should be fine. But how to make a player software slave to USB transmission speed? Is there such a player.<br /> <br /> If we can test whether wavelength DAC is bit perfect, it is going to help understand whether the implementation slave the audio play and USB from end to end. If not, then there would be some resampling by PC which may impact audio quality. <br /> <br /> Anybody test whether Wavelength is bit perfect with USB interface?