Harman Kardon A12 Owners Manual - Page 4

TERMINALS." For speakers with an impedance of 12 to 24 ohms place the Impedance Selector Jumper located near the speaker Terminal strip so that the center terminal is connected to the terminal marked 16. For speakers with an impedance of 4 to 12 ohms place the Impedance Selector Jumper so that the center terminal is connected to the terminal marked 8. The front panel Speaker Selector Switch should then be placed in the "A" position. CAUTION: A jumper is connected between "A" and "B" terminals on the Speaker Terminal Strip on the rear of this instrument. When only one loudspeaker is used, this jumper must be connected at all times. It should he removed only when two separate speakers are connected. This precaution will prevent the set from appearing to be inoperative when only one speaker is connected, and the Speaker Selector Switch is improperly set. Connecting two loudspeakers: if you wish to operate two loudspeakers with the Prelude II and use either one or both together, connect the second speaker to terminals "G" and "B" on the Speaker Terminal Strip. For best operation, both speakers should have the same impedance, although a slight mismatch will not disturb the overall response. To select speaker A, rotate the front panel Speaker Selector Switch to position "A." To select speaker B rotate the switch to position "B." To activate both speakers simultaneously rotate the front panel Speaker Selector Switch to the position marked "AB." OPERATION In general, every control on a well designed, honestly considered high fidelity instrument has a specific useful function, related to each of the other controls. Although this cannot be a treatise on the subject, an explanatory note on the relationship of the various front panel controls will doubtless prove useful in organizing and clarifying them for the user. Your Prelude II incorporates the following operating controls located on the front panel. Viewing the instrument from left to right you will find a Function Selector Switch, Bass Control, Treble Control, and Loudness Control (on/off switch is ,incorporated into this control). Located in the lower right hand corner you will find a Contour Selector Control, and directly above this control is the Speaker Selector Switch. To operate, turn the Function Selector Switch to the RIAA position, and place a recording on your turntable or changer. Turn the amplifier on by rotating the Loudness Control in a clockwise position; now set this Loudness Control at 1/3 volume. Set the Bass and Treble Controls so that the white lines on the knobs point straight up. This will assure a flat response. The Contour Control should remain on zero at this time. Now activate the changer or turntable and play the recording. (If you do not own a changer, a tuner may be used. Merely turn the Function Selector Switch to the "Tuner" position and operate as above.) Now adjust the volume so that the music is played at a comfortable level. Adjust the Bass and Treble tone controls to correct for the electro-acoustical characteristics of the loudspeaker you are using and the acoustic characteristics of the room in which you are listening. Modify each control until settings are chosen which in your total system create the proper sense of aural balance and evenness. Reduce the Loudness (Volume) Control setting to a level somewhat lower than normal listening level in your room. You will note that the full-bodied lifelike quality you experienced at high listening level has disappeared (this because of the Fletcher-Munson effect described in the paragraph on the H/K Dynamic Loudness Contour). With all other controls unchanged, select the best contour setting for you. Do this by switching quickly through the several positions until you find the one which most nearly duplicates the fullbodied sound you enjoyed at high level. Now turn the Loudness control up to the level at which you wish to listen (perhaps the maximum level you can permit in your home). You'll find that there is automatic compensation of contour wherever you set the Loudness control thereafter. In fact, under normal circumstances you should not find it necessary to readjust the tone controls or the contour selector once having chosen the correct settings for you, your room and your system. TECHNICAL EXPLANATION OF THE CONTROLS The Function Selector Switch has 7 positions: Tuner, Aux, RIAA-Rumble, RIAA, LP, EUR, and Tape Head. Its use is to select the desired type of program. Listed below is the explanation of the various functions: Tuner: This position on the Function Selector Switch activates the Tuner jack located on the rear of the chassis. Previously explained under "Tuner Input" section. Aux: This position on the Function Selector Switch activates the AUX jack located on the rear of the chassis. Previously explained under "Auxiliary Input" section. RIAA Rumble: Often, records, record changers and even some turntables produce an objectional low frequency signal that is strong enough to be picked up by the sensitive phonograph cartridge and introduced into the playback system. Known as "Rumble" this undesirable signal can be eliminated by the special Rumble Filter incorporated into the unit. Located on the Function Selector Switch and designated as "RIAA-Rumble" this position effectively "rolls off" the very low frequencies and eliminates rumble. The Rumble Filter is used in conjunction with the RIAA playback curve and the "roll off" is 10 db at 20 cycles. Record Equalization: (RIAA, LP, Eur) In order to assure good reproduction of the wide range of frequencies in music, and to make necessary 3