Appendix D – Audio Interfacing
Appendix D: Audio Interfacing
All analogue audio inputs and outputs are electronically balanced. The screen pins are all directly connected to the chassis at the point of entry to comply with AES/EBU grounding and EMC recommendations.
Balanced Circuits
It is strongly recommended that balanced connections are used wherever pos sible using high quality screened cable. The following diagram shows the recommended connection with both screens connected to the chassis:
| Balanced – Balanced |
| both screens connected to chassis |
| (recommended) |
chassis | chassis |
On some older items of equipment the screen connection may still be referenced to the circuit 0V rather than the | |
chassis. In these cases it may be advantageous to disconnect the screen at this connection. Note however that this | |
practice will degrade the EMC performance. |
|
| Balanced – Balanced |
| one screen connected to chassis |
chassis | 0V |
Connecting to Unbalanced Equipment
Connecting to unbalan ced equipment can be much more problematic. It is much more likely that earth and induced RF currents will become referenced to the audio 0V which will give rise to audible hum and buzz.
The recommendation for connection of balanced to unbalanced equipment is to isolate unbalanced connections | ||
by using a balancing transformer. |
|
|
|
| Balanced – Unbalanced |
|
| one screen connected to chassis |
chassis | 0V | (recommended) |
| ||
|
| |
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