NOTE
THE GFA-5500 IS POLARITY CORRECT AND DOES NOT INVERT PHASE. THAT IS, ANY POSITIVE GOING
SIGNAL AT ITS INPUT WILL APPEAR AS A POSITIVE GOING SIGNAL AT ITS OUTPUT,
Generally speaking, when making connections to the loudspeakers from the amplifier it is very important to use the
correct type and size of wire in order to avoid unnecessary loss of amplifier power in the cable, reduction of amplifier
damping factor and other undesirable conditions. For runs up to twelve feet, ordinary “zip" or lamp cord, made up of
AWG18 stranded wire and available in a variety of insulation colors may be used. For runs up to forty feet, AWG16
stranded wire should be used as a minimum to prevent power losses. For lengths over forty feet and not exceeding sixty
feet, use at least AWG14 stranded wire. Runs exceeding sixty feet require the use of heavier conductors such as
AWG12.
Regardless of the cables you select to connect your loudspeakers, there are some additional requirements which you
should observe in order to ensure maximum performance from your amplifier. It is most important that you make certain
the wiring you have selected has as low a capacitance as possible. All amplifiers, particularly wide bandwidth audio
amplifiers are susceptible to the capacitance cables present to their outputs at extremely high frequencies. This
capacitance, in conjunction with the inductance of the wire itself and the reactive load of the loudspeakers, can create
anomalies at ultrasonic frequencies which, although inaudible, can affect performance in the audible range.
There are several different ways to connect the wiring to the RIGHT and LEFT OUTPUTS, The methods used will
depend on the specific type of connectors supplied with the loudspeakers, the speaker cables, etc. As a matter of
course, we prefer to use banana plugs because it is generally the most secure method of connection. Also, the springs
of the banana plugs create a selTcleaning action which ensures the best contact between the binding posts and the
connectors themselves. There are “sockets" provided in the center of the binding posts’ studs which permit secure
seating of the banana plugs. Before inserting the banana plug into the binding post, ensure the binding post is securely
hand tightened in a clockwise direction.
Additionally, when connecting the cables to the amplifier and loudspeakers, it is important that you “tin” the wires with
good quality electronic solder in order to minimize contact resistance. Tinning prevents the buildup of surface
compounds which can form on copper wire and increase its contact resistance. It is partly for this reason that banana
plugs are preferred. However, make sure that the cable ends are tinned before you make the cable connections to the
banana plugs. Alternatively, you can use “crimped’’ pins or other lugs to ensure low contact resistance at the connection
to the amplifier and loudspeakers.
If you prefer to use other methods of connection, unscrew the insulated head of the binding post until the hole in the
binding post stud is accessible. You can then insert the bare or tinned wire, or terminal pin, through the hole. You can
also use the many variety of spade lugs available by simply placing the tines of the spade lug onto the binding post stud.
Turn the insulated head of the binding post clockwise until the wire or connector is firmly secured. Finger pressure is
sufficient and you should not use pliers or other tools which could damage or over tighten the binding post assembly.
The binding post has been designed in such a way that finger pressure is all that is required to cause a “pinching” action
among the different metal surfaces to ensure proper connection.
All loudspeakers having a nominal impedance down to 4 ohms can be connected to, and driven by the GFA-5500. The
amplifier can drive these low impedances at more than adequate power levels with no difficulty. It should be noted here
that many loudspeaker systems which are nominally rated at 4 ohms drop in impedance, in some parts of their frequency
range, to as low as 2 ohms (and some others to even less than 2 ohms). You will not experience difficulties even with
these very low impedance loads unless you demand excessively high volume levels from the system.
In most applications, you can drive two or more sets of loudspeakers. You should note, however, that when
loudspeakers are paralleled, the impedance presented to the amplifier is lower than the nominal impedance of each
loudspeaker. In other words, if you parallel two 8 ohm sets of loudspeakers, the resultant impedance presented to the
amplifier will be 4 ohms. If 8 ohm and 4 ohm loudspeakers are paralleled, the resultant impedance will be approximately
2.6 ohms. In this last situation, depending upon the lowest impedance of the nominally 4 ohm speakers, and if excessive
power demands are placed on the amplifier, you may trigger the THERMAL PROTECTION on the amplifier or blow one of
the EXTERNAL PROTECTION FUSES. See its respective section for more information. For convenient switching of
multiple sets of speakers with impedance protection for the amplifier, you should consider the use of an ADCOM speaker
selector. These are available from your local ADCOM dealer.
