Adcom High-Current Power Amplifier GFA-555se - Manual (Page 7)

7
CONNECTING THE GFA-555se
When connecting the amplifi er to the loudspeaker, it is vital to maintain proper polarity (positive to positive, negative to
negative). On the GFA-555se , the positive terminal is color coded RED and labeled “+”, and the negative is color coded
BLACK and labeled “-”. The positive terminal on the speaker will be color coded RED, or will be labeled “+”, “pos”,
“positive”, “8 ohms” or “4 ohms”. The negative terminal on the speaker will be color coded BLACK, or will be labeled
“-”, “neg”, “negative”, “C”, “Common”, “G”, or “ground”.
It is recommended that your speaker cables be terminated with “U” type spade connectors. These will give the most
contact area insuring long-term reliability. The spade connector should have a maximum width of 0.57 inches and an
opening width of no less than 0.25”.
To properly connect the speaker cable to the binding posts, turn the insulated head of the binding post clockwise until the
wire or connector is fi rmly secured. Finger pressure is suffi cient and you should not use pliers or other tools which could
damage or over-tighten the binding-post assembly. The binding posts have been designed in such a way that fi nger pressure
is all that is required to cause a “pinching” action among the different metal surfaces to ensure proper connection.
It is very important to use the correct size of wire in order to avoid unnecessary loss of amplifi er power in the cable,
reduction of amplifi er damping factor and other undesirable conditions. Sound audio engineering practice suggests the
use of at least AWG16, stranded, copper cable. Recommended capacitance of the speaker wire should not exceed 5OpF
per foot. This insures high frequencies will not be rolled-off.
All loudspeakers having a nominal impedance down to 4 ohms can be connected to and driven by the GFA-555se. The
amplifi er can drive these low-impedance speakers at more than adequate power levels with no diffi culty. It should be
noted 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 sometimes less). You will not experience diffi culties even with these very low
impedance loads unless you demand excessively high volumes levels from your system.
It is suggested to follow this chart for speaker lengths and wire gauges. If longer runs are needed, it is best to consult
with your ADCOM Dealer to maximize the performance of your system with your exact conditions.
up to 24 feet AWGI6 up to 36 feet AWGI4 up to 58 feet AWGI2
STEREO/BRIDGED MONO INPUT/OUTPUT
The GFA-555se can be used as a very powerful mono amplifi er to drive 8-ohm impedance loudspeakers when in its
“bridged” mode. No modifi cation to the amplifi er is necessary for operation in the bridged mode, nor are any additional
accessories required. However, you will need two GFA-555ses for stereophonic reproduction, if you are using them in
the bridged mono mode.