Going Beyond 96 kHz:

Introduction

The vast majority of currently available music files are at sample rates of 96 kHz or below. As computer audio continues to mature there will be an increasing number of files available at 176.4 kHz and 192 kHz. If your music is 96 kHz and below, skip this page and return to the main menus. All of the instructions on the main setup pages apply to sample rates up to 96 kHz.

Before you attempt to work with files beyond 96 kHz, please go through the normal setup instructions. Make sure that everything is working properly and you are familiar with your system and its software. Only then should you attempt to work with files beyond 96 kHz.

Class Two Audio

Standard computer audio with files up to 96 kHz typically operate under what is called "Class One Audio" which is a subset of USB 1.1. The transmission rate for Class One Audio is 12 MHz. To go beyond 96 kHz requires the use of a protocol called "Class Two Audio", which operates in conjunction with USB 2.0. Class Two Audio uses a transmission rate of 480 MHz, or forty times faster than standard USB computer audio. This means that there is forty times less margin for timing error, and that everything in the signal path must be essentially perfect to achieve good results.

D/A Converter Requirements

All Ayre DX-5 universal audio engines and all QB-9 USB D/A converters manufactured after the summer of 2010 have the capability to handle music files up to 192 kHz and 24 bits of resolution. Older QB-9's may be updated for a nominal fee, either by the factory or by the distributor in your country. In either case, simply take the unit to your local dealer and they will make the necessary arrangements.

To determine if your QB-9 is capable of accepting music files beyond 96 kHz, look at the serial number on the rear panel. The letter in the serial number determines when the unit was made. If the serial number is 18Fxxxx or beyond (e.g., 18Gxxxx), then the unit was manufactured at the factory with the high-speed USB input PCB required to go beyond 96 kHz. If the unit was updated, then the letter "F" (or beyond) will be appended to the original serial number (e.g., 18CxxxxF). If you have any questions, contact your local dealer or distributor.

On the rear panel of both the Ayre DX-5 and QB-9 is a bank of DIP switches. The default that works well for most users is that all switches will be in the "up" position. The switch labeled "Rsrv A" (up) and "Rsrv B" (down) selects the operating class of the unit. Rsrv A puts the unit into Class One Audio mode, and will work without any special drivers as outlined on the main setup pages. Use a toothpick or ball-point pen to flip the switch down to Rsrv B and now the unit will operate in Class Two Audio mode.

Changing the D/A converter from Class One to Class Two is actually one of the last things steps you will want to take during the system setup. There are several more steps to perform with a Mac computer, and many more steps to perform with a Windows machine. You may encounter problems if you change the DIP switch too soon. Don't worry though— you can always just flip the switch up to return to Class One Audio and get sound with music files up to and including 96 kHz.

The USB processor chip only "reads" the position of the "Rsrv A"/"Rsrv B" rear-panel switch upon start-up. As the processor is powered by the USB connection, it is critically important to disconnect and then reconnect the USB cable after changing the position of the rear-panel switch. This will "re-boot" the USB processor and it will then "read" the new position of the switch.

Computer and Operating System Requirements

The requirements for proper operation at the high speeds of Class Two Audio are rather more stringent than for standard (96 kHz and below). These will be detailed on separate pages for Apple and Windows machines.

USB Cable Requirements

The USB cable connecting your computer and D/A converter is one of the most critical components of a Class Two Audio system. Most of the time that we experience reports of problems, it is simply the cable that is at fault.

The USB 2.0 specification lists a maximum cable length of 5 meters (~15 feet). This is marginal with the best of cables, and many "audiophile grade" cables will run into problems even with far shorter lengths. There have been many credible reports of improved sound quality with some cables, but these have almost all been in systems using Class One Audio, with a maximum data rate of 12 MHz. When the data rate is boosted by a factor of 40x to 480 MHz, there are very few "audiophile" cable companies that have the tools and experience to ensure good results.

Regardless of the brand you are best off to use the shortest practicable cable, usually between 1 meter (3 feet) and 2 meters (6 feet) in length. If you need to go longer, be sure to test the actual make and model and length to ensure that it will work properly. Ayre includes an inexpensive USB cable with each unit that provides a good starting point, as it is known to work. The bottom line is to get the system working properly first. Then you can worry about fine-tuning for the best possible sound later.

USB Controller Requirements

The second most common cause of problems with Class Two Audio is the USB controller. This is an electronic circuit ("chip") inside your computer, driving the actual USB connector that is familiar to you. When USB 2.0 was first introduced, the controller chips were simply not finished products. We have had several instances of laptop computers (circa 2005-6) that nominally had USB 2.0 ports but would not work properly. Adding a newer external USB controller via the PC-Card port solved the problem. There is additional detail on this subject on the page for Windows machines.

Regardless of how new your computer (and USB controller) is, there is one cardinal rule —for Class Two Audio the Ayre USB D/A converter cannot share a USB controller with any other devices. Again, we will cover this in more detail in the individual pages for Apple and Windows machines.