ALLEN&HEATH TB1403 - Qu-16 Phantom Power Hot Plugging Page 1/6
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TECHNICAL NOTE
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Allen & Heath Limited, Kernick Industrial Estate, Penryn, Cornwall, TR10 9LU, UK
www.allen-heath.com
Work to be carried out by a competent, qualified engineer.
Allen & Heath cannot be held responsible for the actions of third party engineers.
Risk of electric shock.
Switch mode PSUs may present up to 400VDC.
The factory supported warranty may be invalidated if work is carried out by non-authorized persons.
SUBJECT: Qu-16 +48V Phantom Power Hot Plugging
DATE: June 2014
MODEL(S): Qu-16
We have received feedback from a small number of users who have reported that,
when ‘hot plugging’ microphones on channels with +48V phantom power enabled,
noise can be heard on adjacent channels.
We do not recommend hot plugging condenser microphones when phantom power is
enabled as it could cause damage to your equipment.
However, we understand that occasionally a customer may accidentally hot plug a
microphone when +48V is enabled so we updated the design of the Audio Board
(AG8891) to reduce noise when hot plugging occurs. This update was published as
RECN2963.
We have recently updated the Audio Board to ISS_3 which is explained in RECN2996.
The ISS_3 Audio Board (AG8891_3) is installed in mixers with a serial number of
QU16X-444230 or later. ISS_3 boards do not produce noise when hot plugged.
If a customer complains about hot plugging noise, and has an ISS_2 Audio Board
(AG8891_2), then you can perform a modification to significantly reduce the noise.
If the mixer has a serial number earlier than QU16-003300
Please follow Step 1 (page 3) and Step 2 (pages 4-6) of the document.
If the mixer has a serial number between QU16-003300 and QU16X-444229
Please follow Step 2 (pages 4-6) only.
Please note that this is not a compulsory update and should be performed at your discretion
For further information contact Allen & Heath Technical Support at
www.allen-heath.com/support
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