8
amplifier will amplify any extraneous turn-on noises
those components might generate, which could
potentially damage the loudspeakers.
Good
operating practice dictates that the amplifier should
be turned on last, and turned off first in an audio
system.
The Reference 750 uses a grounding system that
does not require a ground-lifter adaptor plug on the
A. C. power cord to minimize hum. The power cord
supplied with the Reference 750 has a standard
grounding plug to provide maximum safety when
properly connected to a grounded wall
receptacle. If there is any question regarding
proper grounding procedures in your installation,
seek help from a qualified technician. Caution
should be taken before using custom after-market
power cords: they must be at least 12-gauge and
have a standard grounding plug properly installed.
These power cords are to be used with caution, at
the sole risk of the owner.
If electronic crossovers or other AC powered
equipment is used with the Reference 750 it may be
necessary to use “ground lifter” adapters on the
power plugs of that equipment to minimize system
hum. Generally, the lowest hum is achieved when
the only direct connection between audio
common “ground” and true earth ground occurs in
the preamplifier, through its grounded power cord.
Other equipment in the system should have some
form of isolation to prevent ground loops and
associated hum.
Operating Procedure
Start-Up:
1.
Secure input connection between the amplifier
and your preamplifier; attach speaker leads to
the appropriate output terminals.
2
. Attach supplied power cord to rear IEC inlet of
amplifier, and plug other end into grounded A. C.
power receptacle.
3.
Turn on preamp and input source components;
mute preamp output.
4.
Press Reference 750 front panel power switch to
turn unit on; a 45 second mute/warm-up cycle will
follow.
5.
Unmute preamplifier output, initiate source
component signal, and adjust gain as
appropriate.
Shut-Down:
1.
Mute preamplifier output.
2
. Press Reference 750 front panel switch to turn unit
off
3.
Turn off preamplifier and then the associated
input source components.
NOTE: Once you have turned off the
amplifier, please allow at least five
minutes for the power supply to
discharge before turning the amplifier
on again. Turning on tany tube amplifier
immediately following a turn off could shorten the
life of your vacuum tubes or cause tube failure.
Installation of Optional Cover
To install the optional fan-cooled tube cover, first
align the front of the cover with the top front edge
of the amplifier, making sure the fans are positioned
at the rear. Note that there are five holes along the
top edge of each side panel; these should match
up with corresponding holes along the bottom side
edges of the tube cover. Before settling and
aligning the tube cover at the rear, insert the 12V
D.C. plug attached to the fans into the 12V socket
located at the back edge of the anodized top
plate. Then secure and align the tube cover
completely, insert supplied screws and tighten
moderately.
