Electrovox Lc303Pre-Amp 电路图.pdf

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1、AD 15f MAGNETIC PHONO INPUT “LC” preamps are equipped with an RIAA equalizing amplifier circuit. This circuit can be connected or disconnected at time of installation by inserting the “short circuited phone. plug” in the “on” cu the “off” socket at rear of preamp. This circuit should be disconnected

2、 when not in use. us& The phone input cable shield should never be usedto ground the turn-table body tathe preamplifier. A separate conductor should be used and connected to the grounding screw provided on the preamp. near the phono input socket. Severe hum may result, especially with magnetic cartr

3、idges. if this precaution is omitted. TONE CONTROLS AND SPEECH FILTER “LC” preamps are equipped with “Bass” and “Treble” controls. Frequency response is flat when these controls are in center position. Tone controls have no effects on the mic inputs while the speech filter affects only the mic input

4、s. It is therefore possible to obtain high intelligibility from the microphone and at the same time “rich” music reproduction from the other sources. SOURCE SELECTOR While niost program sources can be turned off, turn-tables differ in that the cartridge remains alive and can pick-up noise and vibrat

5、ions even though the motor is turned off. Preamp LC203-U and LC603-U is equipped with a “Phono-Aux” selector. The “Phono” position turns on the crystal or magnetic phono input and the“Aux.” position turns on the other program sources. The Model LC303-U has a I-position source selector. RECORD-PLAYBA

6、CK SELECTOR “LC” preamps are equipped with a “Record-Play” selector. This selector mutes either function to prevent electronic feed-back between the preamplifier and the tape deck amplifier. SUPPLY AND OUTPUT CONNECTIONS “LC” ptermps,in prior productions,were equipped with a length of cable and a ni

7、ne pin plug for connection to the amplifier. On future productions, a screw terminal board will be used on the preamps and the amplifiers to facilitate remote and parallel connection. MASTER VOLUME CONTROL Preamp Model LC603-U is equipped with a master controlThis control should be used for fade-out

8、 only. It should be kept at maximum during all adjustments and normal operating conditions. Bush- ings are available to hide this control when inexperienced personnel is called to operate the pre- amplifier. CIRCUIT IMPROVEMENT The “LC” preamps have higher outputs with plenty of “head room”. A pream

9、p can drive a large number of amplifiers. Inversely 2 or 3 preamps can have their output in parallel to increase the input facilities. Simple bridging circuits and adaptors are available from factory. Inputs have a wide dynamic range, interaction between controls is very low. Frequency response, dis

10、tortion and noise factors are excellent. RadioFans.CN 收音机爱 好者资料库 PREAMPLIFIERS “LC” SERIES AD 151 These newly designed preamps are now replacing the L” Series. One of their main advantages is that the preamp can be mounted at a distance as a remote preamp or can be mounted directly over the amplifie

11、r to form a single unit. These preamps come with hardware for both types of mounting. The power amplifiers will now be supplied with a 7” (17.8 cm) front cover equipped with a monitor speaker. The suffix RM is added to the old number, e.g. LSO40 is now LS040RM. The power amplifiers come with 7” (17.

12、8 cm) mounting brackets. CABINET MODEL CP OlOLS FOR WALL MOUNTING Remains unchanged. . REMOTE MOUNTING OF LS PREAMP. - Install the 3” (7.6 cm) mounting brackets on each side of the preamp and then mount the unit on the rack in the conventional manner. MOUNTING THE “LS” PREAMP DIRECTLY OVER THE POWER

13、 AMPLIFIER IN A RACK Use the 7” (17.8 cm) brackets to mount the power amplifier in the rack, leaving 3-1/2” (8.9 cm) of space over the amplifier for the presmp. Keep the amplifier front cover open and mount the preamp over the cover top edge using the two screws provided. The screws should be pushed

14、 from the-front cover edge into the preamp. Place the nuts over the screws, inside the preamp. and tighten well. The two 3” (7.6 cm) side brackets are used as stoppers and should be mounted loosely on the rack over the 7” (17.8 cm) brackets. Close the cover carefuIly and adjust the 3” (7.6 cm) brack

15、ets to clear the preamp sides, then tighten. MOUNTING THE “LS” PREAMP AND AN AMPLIFIER IN A CP 01 OLS CABINET Diacard the mounting brackets. Mount the amplifier in the cabinet and install the preamp on the amplifier cover top edge as previously described. VUMETERANDOUTPUTLEVEL “LC” preamp comes equi

16、pped with a VU meter. The VU meter is factory adjuated to read t 3 VU with 0.78volt cd output when a steady signal (signal generator) is fed at the input. With an equivalent speech or music signal the reading will seldom exceed 0 VU reference. ADJUSTING THE PREAMP A N D A M P L I F I E R LEVEL . Mak

17、e sure that the loudspeakers and amplifier output taps are correct. Turn down the amplifier input volume control fully counterclockwise. This volume control is located at the extreme left inside the amplifier and should not be confused with the bias control located at center or right end of amplifie

18、r. Feed a signal at one of the preamp inputs (preferably music with strong passages). Adjust the preamp volume control to obtain a good reading on the VU meter, then raise the amplifier volume control until the loudspeakers deliver the desired level MICROPHONE INPUTS Microphone inputs are designed f

19、or low impedance balanced microphones and are now equipped with screw terminals. Cables for microphone lines shall consist of one shielded twisted pair of conduc- tors. The screw marked. “S” is used solely for the cable shield. The two screws marked “L” are used for the two conductors. When the micr

20、ophone or mic line transformer is equipped with a switch on one side of the line, this side, of the line must be connected on the left “L” screw (looking at it from the rear). This line is usually identified by number “2” on the microphone socket, while the other line is identified by number“3” and the ahield by number “1”. .On future productions the three . input screws will be identified as L1 ,L2 and Sl to match microphone and XLR sockets. RadioFans.CN 收音机爱 好者资料库