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Rear Panel Connections

1. Power On/Off  
Switches the 851N on and off.  

2. Mains Voltage Selector Switch (CU Version)  
Switches the mains voltage between 100V and 115V.  

Note: For use by Cambridge Audio service personnel only. 

3. AC Power Socket 
Once you have completed all connections to the amplifier, plug the AC power cable into an appropriate mains socket then switch on. 

4. USB Sockets 
Pre-fitted Wi-Fi dongle and connection for USB HD/flash disk or optional BT100 Bluetooth audio receiver. 

The USB ports are not intended for connection to Apple mobile devices, no functionality, charging or otherwise, is supported. 

The Wi-Fi dongle is pre-fitted. Your unit will default to an Ethernet connection if one is made, however it is advised to remove the Wi-Fi dongle if using an Ethernet connection. 

If you are using this 851N with Wi-Fi please make sure your unit is positioned within range of your wireless router.  

Important Note: Do not connect/disconnect the Wi-Fi dongle when the unit is on. 

5. Ethernet 
Use to connect the 851N directly to a router. 

6. Digital Inputs (D1, D2, D3 and D4) 
TOSLINK Optical and S/P DIF coaxial digital inputs.  

Coaxial – Use a high quality 75 ohm digital RCA Phono interconnect cable (This is different from an analogue audio phono interconnect). This input is suitable for 16-24 bit content up to 192kHz. 

TOSLINK Optical – Use a high quality TOSLINK fibre optic interconnect cable designed specifically for audio use. This input is suitable for 16-24 bit content up to 96kHz (TOSLINK is not recommended at 192kHz sampling rates).  

Note: To obtain the best results from your system we recommend using only high-quality Cambridge Audio interconnects. This will ensure that you hear your system as we designed it. Please ask your dealer for details.  

7. Digital Outputs 
TOSLINK Optical and S/P DIF coaxial digital outputs.  

8. USB Audio In
A USB B type socket to enable the playback of audio from a computer running either Microsoft Windows or Apple Mac OS X operating systems. Some builds of Linux may also be supported but due to the open-source nature of the Linux operating system cannot be guaranteed. 


  • Always use a high-quality USB connection cable certified as USB Hi-Speed. USB cable connections longer than 3m may result in inconsistent audio performance. 

  • Always turn the volume to minimum, switch to another input or turn the 851N off before plugging/unplugging cables to the USB input or whilst booting up/shutting down your PC/Mac. 

  • The use of USB hubs is not recommended for this input. 

9. RS232C Interface 
The RS232C interface enables external serial control of the 851N in custom installation applications, as well as for use by Cambridge Audio service personnel for software updates. 

10. IR In 
Allows modulated IR commands from an IR repeater or custom install systems to be received by the amplifier. 

Commands received by the IR In socket are not looped out of the Control Bus. 

Note: The IR input doesn’t provide any power, so any device connected to this input will need to have its own power source. 

11. Control Bus 
RCA sockets used to send and receive power and volume commands from other connected 851 Series products. For more information on the Control Bus, see Control Bus section. 

12. AES/EBU Balanced  

In – For sources with a balanced (AES/EBU) digital output. This input is suitable for 16-24 bit content up to 192kHz.  

Out – For external devices incorporating a fixed (AES/EBU) digital input. 

13. Line Output 
Line Output (fixed or variable) used to provide a signal to an amplifier or a recording device. 

14. Balanced Audio Output 
For use with balanced XLR connections. The balanced connection is the higher quality option and can reject noise and interference in the cable when used with other equipment that supports this function.  

Note: XLR connectors should be wired as follows: Pin 1: Ground, Pin 2: Hot (in-phase) and Pin 3: Cold (phase-inverted).