Ayre QB-9 USB DAC

AES/EBU is just balanced S/PDIF.

Ayre's asynchronous USB implementation is courtesy of the software written by Gordon Rankin of Wavelength Audio, which Ayre licensed. dCS also has a true asynchronous USB implementation and apparently Resolution Audio's new unit does also. Some other companies throw the term around but I don't think they are legit async USB.

The Weiss Minerva mentioned above, which is now replaced with the new DAC202, uses Firewire, not USB.

Yes aes is the same as spdif but takes more electronics to implement so aes is worse for shorter cables.

Afaik there is only one real asy USB chip in existence in the world and i think none of the mentioned companys use it?

I would refer you back to Hansen's white paper on clocking of data and how SPDIF clocks vs the USB Asynchrounous mode previously mentioned by Almarg.

The only problem with all of this is that some DAC chip designers have designs that are very tolerant of jitter because they already buffer the data onto the chip. IN the case of the Pico seconds of jitter as on SPDIF, the data is already de-jittered by the chip. This is what some video chip designers do.

So, the impact of jitter is not absolute but depends on the chip and implementation. Having said that, the best way around any issues with jitter is to buffer data and reclock it with a new master clock. As long as the device feeding the data (the computer in this instance) is able to keep up with the buffer requests, the DAC will never have to deal with a loss of data condition.

I listened to this dac for 3 straight days in my system and I like it, and respect what it does and how it sounds, but I personally find it lacks excitement and is too laid back for my tastes. Just listen to the Ayre in your system before you give up on the Monarchy. You can get some pretty cool USB adapters that would allow you to hook up the Monarchy to a computer.

Yep, good advice, I plan on taking it slow and learning more before I jump in. I am currently playing with the J-River Media Player and have already discovered that I cannot Rip my SACD's with my current computer (I don't have too many anyway) I also need a bigger hard drive although a firewire drive is cheap these days. It is important to use firewire so you don't overburden the USB bus.

Anyway, will definitely be experimenting and trying things before purchasing but I think it is in the not to far distant future.