LAFAYETTE LA-224T 30W Solid State Stereo Amplifier Instruction Manual

LAFAYETTE LA-224T 30W Solid State Stereo Amplifier

GENERAL DESCRIPTION

• The lA-224T is on all-transistor integrated amplifier designed for high-quality stereophonic or monophonic reproduction. It combines o stereophonic control p, amplifier and 30-wot stereophonic power amplifier in one compact and handsomely designed unit. The advanced all-transistor design offers all the advantages expected from solid-state circuitry-instant worm-up.
• low current consumption … cool operation \ … low distortion and noise … good transient response … wider frequency response at full power. The amplifier has inputs for every type of stereo or monophonic program source­record players, multiple, FM tuners, tape recorders, etc.
• A phonograph input is provided for record players equipped with o magnetic cartridge.
• Tope recorder outputs let you record all stereo or monophonic programs reproduced through the omp­lilier. Speaker outputs consist of just two terms,’°ls for each channel-ail speaker, regardless of whether they are of 4, 8 or 16-ohm impedance, connect to these terminals A full range of controls provides complete flexibility of operation and ensures the finest sound reproduction at all times, regardless of the variations in program sources or room acoustics.
• A special protective circuit employing a fuse in each channel offers protection ogoinst the destruction of Output transistors due to short-circuits in the speaker line. This arrangement is completely effective and will act instantaneously to protect the output transistors
• To obtain the best pertormance from your high-fidelity stereo system. we recommend that you carefully read all the instructions contained in this marual
• Also, we suggest that you keep the manual close at hand and in a safe place so that you can reter to it when necessary.

INSTALLATION

• The amplifier may be used in any convenient location Such as an equipment cabinet, shelt, table or bookcase. Modern and attractive in appearance, the lends itself to this type of installation.
• The amount of heat generated by this amplifier is amplifier
• relatively small compared to vacuum-tube amplifiers.
• Even so, provision must be made tor some ventilation in order to disperse the small amount of heat that is generated.

CONNECTING YOUR ASSOCIATED EQUIPMENT

WARNING
Never insert or remove input cables on the amplifier unless the volume control is at minimum or the amplifier is switched off.

LOUDSPEAKERS
The interconnecting diagram illustrates how speakers are connected to this amplifier. For indoor installations, ordinary plastic-covered lamp cord (No. 18 gauge)
should be used to connect the speakers to the amplifier Before doing so, however, we recommend that you read the following information.
It will enable you to understand one of the basic differences between vacuum- tube amplifier and a transistorized one.

SPEAKER IMPEDANCE

• Transistorized amplifiers which do not employ output transformers in their design need only be equipped with one pair of speaker terminals(for each channel). Thus,
  all speakers, whether 4,8 or 16 ohms impedance, are

• The absence of output connected to these terminals.
  transformers enable the amplifier to produce maximum power ot low distortion levels. In addition, it permits a wider trequency range to be reproduced at high power-particularly in the bass range where large amounts of power are required for proper reproduction.

• With such an amplifier, however, the amount of output power produced will depend upon the impedance of the speaker to which it is connected In this amplifier, maximum output power and minimum distortion will be developed when it is connected to an 8-ohm speaker.

• When connected to a 4 or 16-ohm speaker, the amplifier will develop somewhat lower power. In view of this, it is recommended that identical speakers be connected to
  eoch channel of this amplifier. Speakers of unequal impedance will develop unequal power and thus cause an unbalance in speaker outputs which can only be over-
  come by a considerable increase in the volume of one channel or the other. This would not bea desirable condition.

STEREO HEADPHONES

This amplifier is also designed for stereophonic headphone listening. Simply plug 1he stereo headphones (4, 8 or 16 ohms impedance) into the jock in the front por,el designated PHONES. If you wish 10 si lence 1he Speakers, set the SPEAKERS switch to the OFF position.

TAPE RECORDERS

Recording
All source material selected for reproduction through the amplifier ore internally corrected by the INPUT SELECTOR 10 the TAPE REC jocks.
Use shielded cables with phone plug-type connectors (see LAFAYETTE catalog index CABLES and CONNEC­TORS) 10 connect lo ei1her the high or low-level input of your tape recorder. The output level or frequency response 01 the TAPE REC jocks is unaffected by the settings of the VOLUME, BASS or TREBLE controls.

Playback
The output from recorders hoving their own pre-amplifiers should be connected to The AUX jocks.
To avoid overloading the amplifier, use the volume control of the recorder preamplifier for setting the output level of some. The VOLUME, BASS and TREBLE controls of the amplifier can then be used in conventional manner

STEREO RECORD PLAYERS

The two shielded cables from your stereo record player should be terminated with phone type plugs. To ovoid loss of high frequencies, 1hese cables should not exceed 10 feel in length.

PHONO

Magnetic or variable reluctance (constant velocity type) cartridge should be connected to the jocks designated MAG,

TUNERS

The input jocks designated TUNER ore for use with FM or AM tuners, FM multiplex adoptors, TV receivers and other equipment with at least 0.25 volt output, Shielded coble complete with phono-type plugs should be used lo connect any ol these sources to the amplifier.
The ovtpu1 ol on FM stereo multiplex tuner should be connected as follows:
Connect the tuner’s left channel output to LEFT TUNER jock; connect the tunar’s right channel output to RIGHT TUNER jack. Some applies to AM/FM stereo multiplex tuners. In the case of monophonic tuners, use either LEFT or RIGHT TUNER jocks

OPERATING CONTROLS

INPUT SELECTOR
This switch selects one of the program sources connected to the inputs of the amplifier. The designation on eoch switch posi1ioo indicates the correSponding input which is selected. For example, if the switch is set to TUNER, any equipmen1 con• nec1ed to the TUNER ,nput jocks will be selected.

MODE
The position of this switch determines the manner in which the program source (previously selected by 1he INPUT SELECTOR) shell be reproduced through the amplifier

STEREO position·

• This provides narrator stereo reproduction for stereo programs connected to the inputs of the amplifier

MONO position

Setting the MODE switch at the MONO position combines the s,gr,ols connected 10 L and R channels and provides the same ou1puI on both channels

VOLUME
These ore concentric controls which permit individual adjustment of the volume for each chonnel.
This will allow the scund output of both channels to be “balanced” (see Speaker Phasing and Balancing). The knob closest to the front panel controls the right channel, and rhe other knob controls the left channel.

BASS
This control acts as a master tone control for both channels, either increasing or decreasing the relative level of the bass Oow) tones. When the , indicator line on the knob is in the vertical (12 o’clock) position, response of 1he amplifier is normal)f. Clockwise rotation (from vertical) increases the boss lanes. and counter-clockwise rotation de­creaSG•s rhem.

TREBLE
This control operates in 1he same manner as the BASS control, except tho1 it provides adjustment of the treble (high) 1ones for both channels.

SPEAKER
For Speaker operation, th,s switch must be set 10 the ON Position. To silence the speakers during headphone listening set rhe switch ro OFF.

POWER
Placing this switch In the ON position will switch the unit oo and cause the pilot light to be illuminated.

OPERATING PROCEDURE

Before attempting to operate the amplifier, make Sure that you have connected your program sOurces (record player, tuner, etc.) and correctly. Betore plugging in the amplitier, be loudspeakers
Sure that the power source to be used is 105-125 volts, 50/60 cycles AC, and that the power switch is in the OFF position.

READ CAREFULLY BEFORE PROCEEDING
High-fidelity amplifiers that employ transistors instead of vacuum tubes offer many advantages.
These include such features as instant warm-up, low Current consumption, low heat, low distortion and noise, good transient response and wider frequency response at full power. However, transistorized amplifiers cannot normally be subjected to the same electrical overloads or misuses that vacuum-tube units can survive unless special circuit-protecting devices are incorporated. This has been done in the case of the LA-224T. A special fused circuit is included in the unit to guard against output transistor damage
short circuits at the speaker outputs. The electrical overload which would result from this condition will cause the protective fuse to blow, and thus prevent damage to the output transistors. Blowing of a protective fuse in one or both channels (depending where the short circuit occurs) will cause the sound output to go off permanently in that channel.
Therefore, before proceeding to operate this unit, check
Make sure your speaker connections very carefully that you have not inadvertently created a short-circuit at the amplifier speaker terminals or at the speakers
themselves by allowing strands of the connecting wires to touch the opposite terminals.
Also, if you  have used staples anywhere to secure the speaker cables these staples should be of the insulated type to guard against short-circuits
The protective tuse used in each channel is abampere tast blow type. Do not under any circumstances, use o type of higher rating or one that is not a taste blow type.

OPERATION

1. Set the INPUT SELECTOR to the input you wish to Use, the MODE switch for the type of operation desired, and set VOLUME control to minimum. BASS and TREBLE controls should be set to their mid-position, SPEAKER switch to ON

2. Set the Power Switch to ON. Operate your associated equipment (record player, tuner, etc ) ond increase amplifier VOLUME control for desired level of sound. If you are using a single monophonic program source connected to either LEFT or RIGHT channel, set the MODE switch to MONO. If your program source is stereophonic or separate monorail sources, se1 the MODE switch to STEREO.

3. Adjust, BASS and TREBLE controls to your listening preference.

SPEAKER PHASING AND BALANCING

Correct phasing and balancing,s, important in o stereophonic system. If the Speakers are out of phase. they will work in opposition to each other and there wil1 be o noticeable loss in the low fre­quencies (boss) If the speaker ootput levels ore not equal there will be an unnatural distribution of the musical program, resulting in o loss of the stereo
effect To obtain correct balancing and phasing, use the following procedure. It is based on a simple listening principle which says that if two speakers send an identical sound and you ore equidistant from them, your ears will place the apparent source of sound halfway between the two speakers, as indicated in Figure 2.

• Set the INPUT SELECTOR to PHONO.
  Set MODE switch to STEREO

• Play a monophonic record containing heavy bass tones. Set VOLUME to desired listening level from the speakers.

• For this test, the speakers should be placed about 6 to 8 feet apart and facing inward slightly as shown in Figure 2. You may also require the help of another person to operate the amplifier controls while you position your selt mid-way between the speakers as shown.

• Adiust the VOLUME controls on the amplifier so that the sound output is approximately the same trom both speakers. Listen to the sound output carefully then have someone reverse the speaker leads( and of one channel

• When the speaker output are in phase there will be a slight increase in the bass response and, if the output levels are equal and balanced, the sound source
  will appear to come from a point between the two speakers, as shown in Figure

2. It may be necessary to reverse the speaker leads repeatedly until the correct or
   in-phase condition becomes apparent. Thereat ter, the speaker leads should remain permanently in the positions determined by this test

SERVICE
If any trouble is encountered with this amplifier we recommend that you do the following

1. Make sure that the amplifier is plugged into the correct power source (105-125 volts, 50/60 cycles AC). If the pilot light is not lit, switch the unit off and check the AC 1A. MTH screw-in fuse at the rear of the unit. If the fuse has blown, replace it with one of the same ratings and reinsert it into the amplifier. If the fuse blows again, a fault in the amplifier must be suspected. DO NOT ATTEMPT TO USE A FUSE OF A HIGHER RATING THAN SPECIFIED
2. Check l and R output protective fuses and refer to section under “Operating Procedure which deals with the possibility of failure in output circuits. Also. external speaker selector switches that cause a momentary short circuit when switching from one set of speakers to another may blow these fuses To replace these fuses, press down on the top of the inverted V spring and remove the plastic cover
3. Check for possible errors in control settings. During the following check, never insert or remove interconnecting cables while the amplifier switched on. This could lead to damage.
4. Check all connecting cables between equipment.
5. If trouble was experienced during the initial operation of the system, check all interconnections tor accuracy. Make sure you are using the proper inputs and outputs on the amplifier as indicated in this instruction manual
6. Check to make sure your program source is not at fault (record player, tuner, etc)
   If you have definitely established that there is trouble in the amplifier, DO NOT ATTEMPT TO SERVICE
   IT YOURSELF. Retur n the amplifier to the store from which it was purchased or to LAFAYETTE Service Division, where it will be carefuly checked and any trouble corrected.

SHIPPING INSTRUCTION

Tog the amplifier with your name, complete address and a brief description of the difficulties encountered.
Wrap the unit in heavy paper before inserting into the carton, which should be large enough to permit the use of at least three inches of shredded paper or excelsior between all sides of the unit and the carton. Bear in mind that the carrier will disclaim responsibility for damage it, in his opinion, it was caused by improper packing. Mark the carton FRAGILEELECTRONIC EQUIPMENT” and clearly address as follows:

SERVICE DIVISION
LAFAYETTE RADIO ELECTRONICS CORP 111 JERICHO TURNPIKE SYOSSET, L.I, NEW YORK
Include your own name and address on the carton and ship by prepaid express. The unit will be returned to you express collect

SCHEMATIC DIAGRAM

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