The Mclntosh output circuit, superior in its performance, demands a superior method of
coupling the amplifier output to the loudspeaker load. The MC300 incorporates Mclntosh
designed and manufactured Autotransformers to insure peak performance and protection, as
well as outstanding compatibility between amplifier and speakers.
The MC300 Output Autotransformers have 3 different output impedance tapes for optimum
matching to the particular speaker or combination of speakers being used. Use the following
table to determine which tap should be used. It may be desirable to consult your dealer, or the
manufacturer of your speaker for the best impedance tap to use.
SPEAKER IMPEDANCE AMPLIFIER OUTPUT
IN OHMS CONNECTIONS
2 to 4 COMmon and 2 ohm outputs
4 to 8 COMmon and 4 ohm outputs
8 and up COMmon and 8 ohm outputs
Use high quality speaker cables. The total resistance of the cables must be as low as
possible, so larger diameter, (lower gauge number), cables are most desirable. The longer the
speaker cable is, the lower the gauge number must be to keep resistance low.
RECOMMENDATIONS FOR SPEAKER CABLE LENGTHS AND GAUGE (SIZE)
These speaker cable lengths represent a resistance equal to approximately 5% of the
speaker impedance. The cable sizes are the minimum that should be used. If there is a choice,
the larger diameter cables, (Lower gauge number), should be used.
For 4 Ohm Load
Feet
15
25
40
60
100
Meters
4.6
7.6
12.2
18.3
30.5
For 8 Ohm Load
Feet
30
50
80
120
200
Meters
9.1
15.2
24.4
36.6
61.0
Wire
Gauge
18
16
14
12
10
STEREOPHONIC OPERATION
Connect a cable from the left speaker common terminal to the amplifier LEFT OUTPUT COM
terminal. Connect a cable from the left speaker hot terminal to the amplifier LEFT OUTPUT
(impedance tap desired) terminal.
Connect the right speaker in an identical manner to the amplifier right output terminals of the
correct impedance for your speakers.
If the actual load impedance of a speaker is lower than the specified impedance, particularly
at different parts of the frequency range, it will cause no problems. The high current output
capacity of the MC300 will produce the extra current necessary to properly drive the speaker
under these conditions.
If the impedance of the speaker is higher than the 8 ohm tap, no change in performance
quality will occur. The available power output will simply be slightly less.
The common and hot terminals of both speakers In a stereo Installation must be
connected in an Identical manner to the proper amplifier output terminals. This is essential
for keeping both speaker systems operating IN PHASE. This means that the driving
surfaces of each channel speaker system will move back and forth together. Almost all
speakers have their hot and common terminals color coded, with red usually as hot.
BE SURE THE REAR PANEL MODE SWITCH IS SET TO STEREO.
HOW
TO
CONNECT
OUTPUTS
11
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