Adequate ventilation is a primary consideration when
installing any high power amplifier, because of its appreciable
heat output. Cool air is drawn in through the foam filters on the
sides, and the warm exhaust is to the rear. Make sure this flow is
not impeded, and do not allow the system to work in a closed
box. The
filters
must be kept clean - just slip them out, wash
them, and squeeze dry. Replacements are available from the
Hafler Company, but if you choose to obtain them locally, make
sure you use ‘open cell’
foam for air conditioner filters.
Amplifiers supplied for overseas use with line voltages above
200 VAC use a different fan than those intended for 100 - 120
VAC. If conversion to the other line voltage range is indicated.
be sure the correct fan is obtained from the factory. See “AC
Line Connections for Overseas Use.”
The front panel is designed for mounting in a standard EIA
19” wide rack, using four #l10-32 screws and countersink
washers. It is sufficiently rigid to support the P505 safely. The
panel is slightly under the 7” height to allow clearance between
adjacent units. The feet may be unscrewed from the bottom to
facilitate such installation.
A power transformer of this size will radiate a noticeable hum
field, even though Hafler transformers are specially engineered
to reduce this effect. If the amplifier is likely to be installed
close to equipment which may be sensitive to such a field, such
as microphone amplifiers or other high gain audio stages, be
sure you have adequate separation.
CONNECTIONS
AC Line
A 3-wire grounded power cord is provided on the P50.5. It
must be connected to a properly grounded (earthed) AC
receptacle for your safety. Never break off the ground pin on the
plug to avoid obtaining the proper adapter for 2-wire
receptacles. Do not use cords which are frayed, or whose plug is
damaged. Do not disconnect by pulling on the cord. Grasp the
plug itself.
High power output puts heavy demands on the supply wiring.
Each P505 requires 15 amperes (at 120 VAC) for proper
operation. A separate 20 ampere line is recommended. If
extension cables must be used, keep them short, and use #14
gauge or heavier 3-wire cord.
Input
The amplifier is supplied with standard 2-circuit (tip-sleeve
or T-S) ‘phone’ jacks for normal unbalanced input connections.
These use single conductor shielded cable (shield connected to
the sleeve), or you may choose two wire shielded cable. With
two wire cables, and an unbalanced input, the signal, or ‘hot’
(black) lead connects to the plug tip and the ground (white or
red) lead connects to the sleeve. Hum is usually minimized in
two wire cable by connecting the shield to the ground wire at
one end only.
¼’ PHONE PLUG
INSULATING PLUG BODY
SLEEVE
SHIELDED
CABLE
SHIELD
MAY BE CONNECTED
G R O U N D LUG
(see
TEXT)
TO
If very long input signal cables are required, a balanced input
is usually advisable, using two wire shielded cable, and adding
the Hafler BL500 option, which eliminates the need for
hum-sensitive external input transformers. Then the 2-circuit
(T-S) phone jacks may be replaced by 3-circuit (tip-ring-sleeve
or T-R-S) jacks, wired with the ‘low’ (white or red) lead to the
ring, and the shield to the sleeve. Or, 3-pin ‘Cannon XLR’
connectors may be installed via the chassis knockout provided.
The XLR connectors are often preferred for either balanced or
unbalanced lines because of a locking provision. Because there
are two wiring standards, you want to make sure all your
equipment is consistent. The IEC International standard
connects the shield to pin # 1 and the signal (‘high’ - black wire)
to pin #2. On a balanced line, the return (‘low’ - white or red
wire) would go to pin #3. The defacto American standard,
which is not as widely used, interchanges the connections to the
#2 and #3 pins.
Some applications may require the use of an input
transformer, to convert balanced lines to unbalanced
connections ahead of the power amplifier. Such transformers
are very sensitive to magnetic fields, such as those generated by
the power transformer. You may have to install them a fair
distance from the P505 to avoid hum pickup.
Output
The red and black binding posts were chosen for heavy duty
construction to handle the high currents which may be involved.
They are spaced for dual banana plugs, or you can connect bare
wire ends through the vertical holes in the shafts, which are
visible when the cap is unscrewed. To be certain that no wire
strands are unsecured, a tinned end, or a spade lug soldered to
the wire is recommended.
4
filters
