Bryston 280 b schematic

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TECHNICAL MANUAL

280-8

NOESE REDUCTION INTERFACE

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IMPORTANT INFORMATION
WHEN USING THE 2808 INTERFACE

BATTERIES: CAUTION - WEAK BATTERIES MAY BLOW 280B FUSE

THE 2808 USES A WIDE INPUT RANGE POWER CONVERTER TO
PROVIDE A REGULATED 24 VOLTS FOR THE NOISE REDUCTION
CARDS. WHEN THE BATTERY VOLTAGE FALLS THE CURRENT
REQUIRED INCREASES. SHOULD THE BATTERY VOLTAGE BECOME
LOW ENOUGH (8 TO 9 VOLTS) THE CURRENT CAN EXCEED THE
RATING OF THE PROTECTIVE FUSE. BATTERIES THAT APPEAR O.K.
IN THE UNATTACHED NAGRA IV-S MAY FAIL QUICKLY WHEN TRYING
TO POWER BOTH UNITS. (USE ONLY 2AG FUSE 2 AMPS)

USE ONLY FRESH ALKALINE TYPE CELLS AND CHANGE AS SOON AS
POSSIBLE SHOULD LOW POWER INDICATOR FLASH. NICAD CELLS
WITH 4 AMP HOUR RATING OR BETTER ALSO MAY BE USED WITH
REDUCED LIFE. (SEE BATTERY CHART IN TEXT)

THE 2803 DRAWS CURRENT WHEN THE NAGRA IV-S IS IN "STOP"
MODE. SELECT POWER AWAY FROM BATTERIES WHEN NOT IN USE.

POWER SUPPLY:
NAGRA "ATN" POWER SUPPLIES WILL NOT POWER BOTH THE 2808 AND
THE RECORDER. A 15 WATT REGULATED 24 VOLT SUPPLY WITH LOW
NOISE AND RIPPLE WILL POWER BOTH UNITS.

INPUT CABLE:
THE CABLE FEEDING THE LINE INPUT OF THE 280B MUST NOT HAVE
SERIES RESISTORS. SEVERE LEVEL LOSS WILL WILL RESULT.

MODIFICATION OF NAGRA IV-S FOR -IOR IN "TEST"

"TEST" POSITION ON THE NAGRA IV-S MAIN FUNCTION SWITCH WILL
CAUSE A FEEDBACK LOOP TO BE FORMED UNLESS THE RECORDER
OUTPUTS "-1OFI" IN THIS SETTING. BRYSTON CIRCUIT BOARD "2808-
NAG" SHOULD BE INSTALLED IN RECORDER TO PREVENT THIS
PROBLEM FROM OCCURRING. INSTALLATION DETAILS ARE INCLUDED.

AUDIBLE FEEDBACK LOOP DURING PLAYBACK:
CARE SHOULD BE TAKEN DURING DECODED PLAYBACK THAT THE
"TAPE/DIRECT" SWITCH ON THE IV-S RECORDER IS IN THE "TAPE
POSITION. SELECTING PLAYBACK WITH THE IV-S "TAPE/DIRECT
SWITCH SELECTED TO "DIRECT" WILL CAUSE THE SYSTEM TO
FEEDBACK, CREATING AN UNPLEASANT MONITORING CONDITION.