Use with Macs
No extra drivers are required. With the 751R switched to USB Audio 1.0 the
751R will work with the native Mac OS-X 10.5 (Leopard) or above Audio 1.0
driver and accept audio up to 24-bit/96kHz.
With the 751R switched to USB Audio 2.0 the 751R works with the native
Mac OS-X 10.5 (Leopard) or above Audio 2.0 driver and can accept audio up
Use with Linux
For most distributions of Linux with the 751R switched to USB Audio 1.0 the
751R will work with the native Audio 1.0 driver and accept audio up to 24-
Some very new distributions of Linux are now supporting USB Audio 2.0 for
which the 751R should be switched to Audio 2.0 support to accept audio up
For both cases because Linux distributions vary according to their creators
choice of software components including drivers it is not possible to
guarantee operation and Audio drivers may need to be loaded.
‘Class drivers’ as they are called for generic support of Audio Class 1.0 or
Audio Class 2.0 devices may be available from the Linux community, we do
not supply these.
Bit perfect transfer – ASIO and WASAPI Exclusive mode
The 751R USB interface hardware and software support bit perfect transfer.
Whether or not the audio sent to the 751R is bitperfect (i.e. not resampled
or mixed etc. by the PC) is actually a function of the playback application and
the operating systems audio engine.
By default the standard windows audio drivers (often called WDM drivers)
included in Windows XP support MME or DirectSound transfer, both of which
include a kernel mixer and re-sampler stage.
One way round this is to use ASIO to bypass this. Another is to use a playback
application that supports its own form of kernel streaming, i.e. if has its own
way of outputting the audio without invoking the kernel mixer.
For Windows Vista and Windows 7 a new method of audio transfer is
supported called WASAPI. This has two modes; Shared and Exclusive. Shared
mode is similar to MME or DirectSound but in Exclusive mode the kernel
mixer/re-sampler is bypassed and bit perfect transfer is possible with only
one audio playback program directed to the soundcard at a time (for
instance system sounds are not mixed in).
To ensure bit perfect transfer use a playback application that supports ASIO,
WASAPI in Exclusive mode (if you have Windows Vista or Windows 7) or some
form of kernel streaming.
This is a fast moving area so we would encourage you to check the web for
the latest media players to support these more audiophile playback options.
To use ASIO you will need the Cambridge Audio Sound Driver installed and
the 751R switched to USB Audio 2.0.
No further settings are required as the driver automatically supports ASIO
transfer, all that is required is to load and setup suitable ASIO enabled
ASIO (Audio Stream Input/Output) is a non Microsoft audio driver protocol for
Windows originally invented by Steinberg Ltd ASIO bypasses some of the
normal audio path from the playback application through the Windows audio
system (including the Kernel Mixer) for a more direct path to the 751R.
You will need to install and use a suitable playback application that supports
ASIO output either natively or via a plugin. One example of such an
application with a suitable plugin is Foobar, see http://www.foobar2000.org
for more details.
USB Audio (751R only)
The 751R is both USB 2.0 (Hi-Speed) and USB 1.1 (Full-speed) USB port
The 751R also supports two USB Audio protocols (not the same as the port
types themselves) USB Audio 1.0 (which works over USB 1.1 ports and
supports up to 24-bit/96kHz) or USB Audio 2.0 (which requires a USB 2.0
port and can support up to 24-bit/192kHz).
The default configuration is USB 1.1 and USB Audio 1.0 which works with
nearly all common operating systems and computer types without drivers
and supports up to 24-bit/96kHz audio, simply plug in and play.
In this configuration the 751R is able to work at up to 24-bit/96kHz by
declaring to your computer that it can handle any sample rate from 32kHz to
However in some Windows/Mac operating system variants the operating
system itself may restrict or fix the output sample rate or re-sample the
See our online guide at www.cambridge-audio.com/751RSupport on USB
Audio for more details on this. With careful choice of playback software and
settings many pitfalls can be avoided.
In particular our free Windows USB Audio 2.0 driver (available from our
website) supports up to 24-bit/192kHz audio and WASPI Exclusive or ASIO
modes that can give enhanced performance.
A brief explanation of your choices is below:
Switching between USB Class 1 and USB Class 2
Your 751R will come set to driverless USB Audio Class 1.0 by default, but it
can be configured to run in either USB Class Audio 1.0 or 2.0 mode. To
change USB Class, navigate to the Advanced Audio Setup menu and select
the USB Audio item.
Use with PCs
With the 751R switched to USB Audio 1.0 (this is the default setting) the
751R will work with the native Windows XP, Vista or 7 Audio 1.0 driver (no
need to load any new driver) and accept audio up to 24-bit/96kHz.
With the 751R switched to USB Audio 2.0 the 751R needs the Cambridge
Audio USB Audio 2.0 Driver to be loaded and can then accept up to
24-bit/192kHz (and support ASIO and WASAPI Exclusive if required).
The driver is available from www.cambridge-audio.com/751RSupport.
USB ‘B–A’ type lead