User manual MCINTOSH MAC4280

[. . . ] Your Mclntosh authorized Service Agency can expedite repairs when you provide the Service Contract with the instrument for repair. To assist, record your Service Contract number here: Service Contract Number Your MAC 4100 Solid State AMFM/FM Stereo Receiver will give you many years of pleasant and satisfactory performance. If you have any questions, please contact: Contents INTRODUCTION . . . 2 INSTALLATION. . . 3 HOW TO CONNECT. . . 5 WHAT THE FRONT PANEL CONTROLS DO AND HOW TO USE THEM. . [. . . ] Here are some suggestions from which to start: Problem Equalizer Correction Bass too weak Raise 30 and/or 150 Male vocalist needs reinforcing Raise 150 Female vocalist reinforcing Raise 500 Hum on program Reduce 30 Violins, trumpets dull Raise 1500 Drum "brushes" not audible Raise 10 K BALANCE and LOUDness The BALANCE and LOUDness controls are concentric. The BALANCE control [large outer knob] adjusts for equal volume of either the left or right channels. The volume of the channels can be varied relative to each other without affecting their combined volume. turning the control to the left accents the left channel by reducing the right channel output. turning the control to the right accents the right channel by reducing the left channel output. The LOUDness control [small center knob] increases both bass and treble frequencies of both channels as it is turned clockwise. Adjustment of the LOUDness control allows life-like frequency balance when playing music softly. Its contour is the same, regardless of the position of the volume control. This contour is accurately modelled after the family of "Equal Loudness" curves identified by Fletcher and Munson. The loudness circuitry is completely independent of the volume control. Therefore, any desired amount of compensation can be introduced regardless of volume control position. 1 dB. With POWER GUARD operating the output waveform distortion is limited to 1 %. INPUT INDICATORS At the bottom right of the tuning dial area are eight LEDs, six indicate the status of the INPUT SELECTOR switch. The illuminated LED indicates the program source selected. The two remaining LEDs indicate AFL and FM MPX. AFL indicates the operation of the automatic frequency lock circuit showing that the tuner is correctly tuned to the center frequency of the FM station. FM MPX - indicates the FM station is broadcasting a 19 kHz pilot signal necessary for the transmission of FM stereo programs. It denotes the station is broadcasting stereo. Balancing Your Stereo The performance and enjoyment of a stereo system is greatly increased when the sound is properly balanced. The balance of the stereo system is affected by many things including room acoustics, furniture placement, room shape, small differences in loudspeakers etc. Factors that affect proper stereo balance are correct phase for both channels and equal program loudness. If the sound is not directly in front of you, reverse the leads on one of the loudspeakers only. When the sound comes from the midpoint between the speakers they are in phase. If there is a difference in loudness, turn the BALANCE control toward the speaker that is not as loud. Adjust the BALANCE control until the sound is balanced between both speakers. TO ADJUST PHASE Press the MONO pushbutton. [. . . ] The MAC 4100 power amplifier is direct coupled to insure maximum low frequency performance. In most direct coupled circuits, failure of any transistor in the power amplifier will cause a DC potential to appear in the output. To assure that no damaging or interfering DC appears across the output terminals, a special, very fast acting protector circuit constantly monitors the output circuit for DC. If, at any time, a constant DC level appears, the speakers are disconnected. [. . . ]