Optional Phono Preamp Module

Asynchronous Audio

The asynchronous mode USB converter in the m905 represents significant improvement over any previous type of USB DAC. Previously, a USB DAC worked under standard adaptive mode USB audio, which means the DAC’s clock would have to sync to the non-audio related computer USB buss master clock. As you can imagine, the computer has a lot else to do, so the incoming clock signal to which the DAC’s clock would have to sync was not ideal and would result in unwanted jitter.

With asynchronous mode USB, the m905’s USB DAC becomes the master to which the computer’s USB buss gets synced. So the computer is now synced to a crystal-based audio clock signal and the systems works with dramatically lower jitter. No phase-lock loop or sample rate conversion necessary, which means bit-perfect playback from a computer with zero interface-induced jitter.

Computer Audio Requirements

Regardless of the type of computer you will use to playback audio from, it must have at least one available USB port. The m905 ships with a standard USB type A to type B cable. The type A connector plugs in to the computer and the type B connector to the USB m905 input.

The m905’s asynchronous mode USB DAC supports standard driverless operation on MAC to 192kHz and on PC to 96kHz. For sampling rates above 96kHz, PC users will need to download and install a free driver on their computer. This driver can be found on our website – http://www.gracedesign.com/support/support.htm
Driverless operation basically means ‘plug and play’. The m905 will automatically show up in your computer’s list of supported audio devices as ‘Grace Audio Device’. In most cases, simply choose that as your audio playback device and the system will work.

Different operating systems may pose their own set of complications in setting up the m905 as the audio playback device. In the event that ‘plug and play’ operation does not occur, you will need to look at some specific setup variables for your OS. In this case, we will direct you to a very well written and comprehensive docu­ment by our friend and colleague Charlie Hanson from Ayre Acoustics. http://www.ayre.com/USB.htm. This is an invaluable resource for computer/USB audio setup information for most all current operating systems, and we strongly urge you to familiarize yourself with the information pertaining to your specific OS.

Another excellent resource is Wavelength Audio’s website: http://www.USBdacs.com
In the event that you have any setup issues which aren’t addressed by these resources, feel from to contact us directly at 303.443.7454 Monday through Friday 9 – 5, MST.

Using the m905 for DAW playback

With the extremely high quality audio playback achieved with this USB interface, the m905 can be great option as an stereo output device directly from your digital audio workstation. For playback only, this will work very well. However, using it in conjunction with other USB audio devices connected to your workstation computer’s USB will require some adjustments to your computers audio settings and for best results, some external clock routing between audio devices.
For Mac OS X, this is achieved by setting up the m905 in an ‘aggregate audio device’ setup, with the m905 as the output device. For Win 98 – Win 7, you must use ‘asio4all’ drivers- http://www.asio4all.com/. There is currently no support yet for windows 8.

With both of these setups, if you are using multiple I/O devices, you will need to pay careful attention to clocking. In Mac / Core audio aggregate setups, you are able to set which device is the clock master. However, this means that other devices will be sample rate converted, which we do not recommend.

Jonathan Wyman is a producer/mixer/engineer based out of Portland, Maine. For a number of years, the m904B was at the heart of his monitoring system. Recently, he retired that unit in his A room and installed a new m905. Here’s what he had to say about the new rig:

“The monitoring in a studio informs every decision I make, so it’s been a priority for me to have the most accurate chain possible. I need the flexibility to be able to compare various sources: my mix, the rough mix, commercial references, even something my client wants to play me on their iPhone. Finally, it has to be musical, so I don’t hate the entire world at the end of a long day.

“The m904B was a game changer when I got it nine years ago, and the m905 is a step up that is not subtle at all. Improved ergonomics on the remote, built in SPL metering, and super flexible calibration have made a positive difference in my daily workflow. The sub mute is cool for visiting engineers who may not be used to the 2.1 setup, and the third set of speaker outputs make it a breeze if a visiting engineer wants to use their own speakers.

“But the biggest difference is the sound of the unit. The imaging is really detailed, and the speakers just kind of go away. The DAC sounds awesome, and it’s great to have a common converter to compare all my digital sources. It’s super musical and pleasant to listen to when things are right, but it’s not shy at all about showing me where things are wrong. It was immediately an improvement over the already great sounding m904B (which is still going strong in our B room – testament to how well these things are built!).

“My m905 helps me to instinctively make quick, confident decisions about my work. I absolutely love it.”

Please visit Jonathan’s website here

Owner’s manual Rev E