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Maintain a consistent polarity with respect to the ‘hot’ and

‘ground’ wires to the speakers. Most dual banana plugs have a

tab  identifying one side,

which  is customarily made the

‘ground’ side. In stereo speaker installations it is important to

keep consistent phase relationships to preserve low frequency

response and stereo ‘imaging’ perspective. This means that the

same  wiring ‘sense’   should  be followed when wiring each

speaker.

D U A L   6AWAMA PLUG

S P A D E  

S I N G L E   BANANA

 

PLUG

The  black output terminals may be connected together

(common ground) when accessories utilizing a common ground

system,  such as headphone junction boxes, are employed.

However,  the 

red 

terminals  should 

never 

be  connected

together. Thus you should carefully check connections when

using a common ground device, to be sure there is no reversal of

the ground and high side.

Connecting Cables

The  permissible cable length for an unbalanced input is

determined by two factors: the cable capacitance per foot, and

the output impedance of the signal source, which is a function of

the design of the output stage of the source (control center).

Cable capacitance is part of the ‘load’ on the signal source. As

the capacitance increases, the effect is that of a progressive filter

which rolls off the high frequencies before they reach the power

amplifier.  The amount of the roll off increases as the output

impedance goes up. With most control centers and normal input

cables (under 20 feet) the filter effect will be above the audio

range. If the output impedance of the source exceeds 500 ohms

at 1000 Hz, a high cable capacitance may cause oscillation in

the  source equipment. Shortening the cable, or choosing a

special low capacitance cable type may solve the problem. If

very long signal cables are required, converting to a balanced

input is the best solution. The Hafler  BL500   balanced input

option may be installed in the  P505, and avoids the need for

hum-sensitive input transformers.

The  choice of shielded wire for input cables may involve

more than just the capacitance per foot. Where resistance to

abuse is a factor, the rubber-clad cables with woven shielding

outperform  vinyl coverings. The vinyl insulation is usually

supplied with a foil shield which can be easily tom, so plugs

must  be wired with great care. If permanent wiring involves

‘fishing’ cables through conduits, the vinyl cable is easier to use

because  it has less surface resistance, but the foil shield is

susceptible to splitting with undue stress.

Some thought should also be given to selecting the output

cables. When high power is demanded from the amplifier, the

impedance of the output cables becomes part of the loudspeaker

load.  The desirably high damping factor of Hafler amplifiers,

which  is an index of the amplifier’s ability to control the

speaker, is reduced by excessive cable impedance. Even more,

long  runs of inadequate wiring waste power. The following

chart illustrates typical power dissipation with a 4 ohm load.

The  lowest gauge, or heaviest practical wire size is always

preferred. When very long output cables are required, the use of

balanced  70 volt lines is recommended. The Hafler LX250

transformer can provide a 70.7 volt output from one channel of

the  P505.   The rated available power per channel is the

equivalent of its 8 ohm output of 255 watts. Predrilled holes in

the  amplifier’s cover can   accomodate two  transformers. The

output voltage of a  P505 operated in the monophonic bridged

mode is sufficient to drive a 70 volt line directly without the

need for a transformer.

Wire Gauge

Power Loss in Watts @ 4 ohms

(A.W.G.)

25’ 

cable

100’ cable

6

1.8

6.9

10

4.4

17.3

14

11.1

41.3

18

26.8

91.2

Monophonic Operation (Bridged Mode)

When very high power is desired, the P505 can be switched to

a single channel amplifier, capable of delivering more than 800

watts into an 8 ohm load. For this, the Stereo-Mono slide switch

is moved to Mono, and an input signal is applied to the Left

input jack only. The two output leads are connected only to the

Red  terminals, and no connections are made to the black

terminals. The output must be ‘floating’  - that is, neither side

can  be grounded, as both are ‘hot’ with respect to chassis

ground. The red terminals are identified ( + ) and ( - ) simply for

phasing reference. In this mode, the  P505 can drive a 70 volt

distribution  line directly. Sensitivity is adjusted by the Left

input level control.

5

Summary of Contents for P505

Page 1: ...PERATION CAUTION IF THE SPEAKER FUSES BLOW SOME DISTORTED SOUND CAN BE HEARD THEREFORE IF AMPLIFIER MALFUNCTIONS ALWAYS CHECK FOR BLOWN FUSES FIRST LM135 THE DAVID HAFLER COMPANY 5910 Crescent Boulevard Pennsauken New Jersey 08109 Hafler P505 Professional Power Amp ...

Page 2: ...ferred to 1 watt into 8 ohms A weighting Input Impedance 47 000 ohms in parallel with 50K ohms input level control Input Sensitivity 2 35 volts for 255 watts into 8 ohms 0 14 volt for 1 watt 2 volts for 400 watts into 4 ohms 0 08 volt for 1 watt Damping Factor 200 to 1 kHz into 8 ohms 60 to 10 kHz into 8 ohms Rise Time 10 kHz 80 volts p p square wave 10 to 90 2 5µs Slew Rate 1 kHz 120 volts p p sq...

Page 3: ... and equipment service and provides a high level of protection to associated equipment and operating personnel P505 POWER AS A FUNCTION OF IMPEDANCE POWER PER CHANNEL BOTH CHANNELS DRIVEN The P505 incorporates a number of protective devices Separate power supply fuses for B and B on each channel individual thermal sensors on each heat sink a relay to disengage the output if excessive DC offset is ...

Page 4: ...avier 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 ...

Page 5: ...r the rubber clad cables with woven shielding outperform vinyl coverings The vinyl insulation is usually supplied with a foil shield which can be easily tom so plugs must be wired with great care If permanent wiring involves fishing cables through conduits the vinyl cable is easier to use because it has less surface resistance but the foil shield is susceptible to splitting with undue stress Some ...

Page 6: ...al having a specific porosity so exact replacement is best They may be ordered from the Hafler Company as part AF002 6 Back Panel Controls An input level control adjusts the sensitivity of each channel They are usually left at full clockwise rotation for maximum sensitivity and best signal to noise ratio Then 2 volts will drive each channel to full output 4 ohm load These controls have a B taper w...

Page 7: ...50 or 60 Hz power lines The Export version includes an additional terminal strip to terminate the extra transformer leads In units supplied for 200 volt and higher AC lines the line fuse is a 7 ampere slo blo type and a different fan is installed along with different fan controlling power resistors which are mounted on the underside of the audio module The diagrams below show schematically and pic...

Page 8: ...low impedance load where the fuse sizes may need to be increased If the amplifier requires factory service and the power transformer output appears normal when its secondary leads are disconnected from the diode bridge the transformer can be removed and the rest of the amplifier returned for service This greatly reduces the cost of shipping and the risk of damage in transit If you have isolated th...

Page 9: ...iven in the event of excessive signal levels The output current is limited by the B and B fuses and the speaker fuses A protective relay circuit has a j section low pass filter which prevents signals above 10 H z from triggering the relay This circuit allows direct current to pass to IC101 which senses any offset above 3 5 volts and then opens the relay to protect the load RI06 and R107 form the r...

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Page 12: ...ch QBI I5 TAI I2 RPOI I RPOI I RF036 TAI I6 TAI I7 SZI 13 SLIII s402 S403 TR40 I TR402 TR40 I TS40 I TS402 DPDT slide switch DPDT slide switch Thermal breaker Thermal breaker Inrush limiter Thermal sensor Thermal sensor Fan I20 volt Fan 200 240 volt alternate SCHEMATIC DIAGRAM P505 PowerAmplifier r Copyright 1985 All rights reserved SZl22 SZl22 S F 0 2 4 S F 0 2 4 RZOl6 S F 0 2 5 S F 0 2 5 AAI I4 ...

Page 13: ...anty 4 A description of the malfunction under occurred and whether it is intermittent what conditions it You are responsible for proper packing Insure it for the retail value United Parcel Service is suggested for domestic shipments and is the usual carrier for its return Units which required service under the warranty will normally be returned by UPS prepaid within continental USA Other return sh...

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