STEREO PREAMP-AMPLIFIER MA230 GENERAL DESCRIPTION 1 TECHNICAL DESCRIPTION Mechanical Specifications Electrical Specifications 1 3 3 FRONT PANEL INFORMATION 5 INSTALLATION CONNECTIONS TABLE OF CONTENTS AC Connections Ground Connection Tape Output Connections Loudspeaker Connections AC Power Input Connections 9 11 11 11 12 12 12 12 OPERATING INSTRUCTIONS 14 GUARANTEE 20 3-YEAR FACTORY SERVICE CONTRACT 20 MA230
MA230 PREAMP-AMPLIFIER GENERAL DESCRIPTION The new Mclntosh MA230 presents two outstanding "FIRSTS" for your home stereo listening enjoyment. . . . The MA230 is the FIRST stereo preamp-amplifier on one chassis that meets the traditional rigorous Mclntosh engineering performance standards. . . . The MA230 is the FIRST stereo instrument to combine a solid state preamplifier with a tube and transformer power amplifier on the same chassis.
each channel of the tone control section. The entire preamplifier has low noise, low distortion, and is not affected by normal room temperature variations. Typical Mclntosh care in design protects against input signal overload. Both the high level inputs (Tuner, Tape and Aux) and the low level phono and tape head inputs can accept much higher than average input signals without overload. For example, at 2000 cycles the phono inputs can-accept 150 millivolts of signal before overload.
couples the output tube cathodes into the transformer. Six db of negative feedback is produced in the output stage with this circuit. Twenty db of negative feedback around the entire power amplifier circuit is achieved by coupling a special secondary winding on the output transformer back to the first stage 12AX7 cathode. The fixed bias on the 7591 output tubes is adjustable over a small range with individual controls. These adjustments are factory set to 0.7 volts DC at the test points.
Frequency Range At 30 watts output both channels. + 0, -0.5db 20 cycles through 20,000 cycles. +0, - 3 d b 15 cycles through 70,000 cycles. Output Impedance 4 ohms, 8 ohms, 16 ohms. Internal Impedance/Damping Less than 10% of rated load impedance; damping factory of 10. Input Sensitivity and Impedance Auxiliary, Tape, Tuner, and Tape Monitor: .25 volts, 250K ohms. Phono 1 and Phono 2: 1.5 millivolts, 47,000 ohms. Tape Head: 1.5 millivolts, 1 Megohm.
FRONT PANEL INFORMATION Figure 1. MA230 Front Panel. INPUT SELECTOR 6. TAPE HD: Use the TAPE HD (Tape Head) position for a tape deck that does not have its own playback preamplifier. The Tape Head leads are connected to the back panel TAPE HD input jacks. MODE SELECTOR Figure 2. INPUT SELECTOR Switch. Select any of six program sources with the MA230 INPUT SELECTOR switch. 1.
Turn the MODE SELECTOR to: 1. L TO L & R: connects the "left" input to both loudspeakers. 2. R TO L & R: connects the "right" input to both loudspeakers. 3. STEREO REV: connects the "left" input to the "right" loudspeaker and the "right" input to the "left" loudspeaker. 4. STEREO: connects the "left" input to the "left" loudspeaker and the "right" input to the "right" loudspeaker. 5.
The MA230 TAPE switch makes it possible to instantaneously compare recorded material with the source signal. Use the MA230 TAPE switch to know instantaneously, as you are recording, that the music on the tape is acceptable. Tape monitor jacks on the back panel accept a signal from a tape recorder with a monitor head and preamplifier. NORMAL . . . the original program source is fed through the power amplifiers and the loudspeakers. MONITOR . . .
LF (Low Frequency Filter) LOUDNESS Use the LF filter to reduce low frequency noises created by a turntable, record changer, or vibration acoustically coupled to the phono player from the speakers. FLAT.. .filter disconnected; flat response. FILTER . . . low frequencies reduced sharply below 50 cycles. When you turn down the volume, music seems to lose much of its bass and some of its treble. This effect is due to the sensitivity characteristics of human hearing.
INSTALLATION The MA230 can be installed in furniture cabinets, custom built installations or professional relay racks. If the unit is to be used on a shelf or table top, it can be housed in an attractive Mclntosh cabinet. Allow sufficient cabinet space for air circulation. Minimum internal cabinet dimensions should be at least 16 inches wide, 14 inches deep, and 6 inches high. The back of the cabinet should be left as open as possible for ventilation.
4. Cut out the rectangular opening. Figure 19. Installation Cutout. 5. Secure the mounting strips to the inside of the panel. Tighten the flat head screw so that the screw head pulls in the wood panel level with the panel surface. Repeat this with the second mounting strip on the other side of the rectangular cutout. 6. Left and right metal mounting brackets are packed with the MA230. Fasten these two mounting brackets to the cabinet panel using four of the fillister head screws.
CONNECTING AC CONNECTIONS There are three AC outlets on the back panel of the MA230. The black receptacles have a maximum power rating of 350 watts total. The power to the two black receptacles is controlled by the front panel power switch. Use these receptacles for accessories such as a tuner and tape recorder. The red receptacle is not switched. Use the red receptacle for powering a turntable or record changer.
gram source should be twisted together and the ground wire from each source can be wound or twisted in with these cables. To avoid hum, make sure the ground wire does not make any connections to shields of the left and right channel cables except for the connection provided with the MA230 ground post. TAPE OUTPUT CONNECTIONS The TAPE OUTPUTS on the back panel provide the program material with sufficient level for feeding a tape deck or recorder.
DIRECTIONAL FM ANTENNA ROTATOR GROUND TO 12OV AC OUTLET 8 OHM SPEAKERS SHOWN 13
If a phono cartridge requires less than 47,000 ohms load impedance, a resistor can be added across the terminals of the car- tridge to achieve the correct termination. The following chart may be used as a guide: Desired Impedance Resistor Across Input 47,000 37,000 27,000 15,000 6,800 No Resistor 180,000 ohms 62,000 ohms 22,000 ohms 8,200 ohms ohms ohms ohms ohms ohms (47K) (37K) (27K) (15K) (6.8K) (180K) (62K) (22K) (8.
source of sound should appear to be directly in front of you. Alternate the PHASE switch between 0° and 180°. If the sound is not directly in front of you in the 0° position, reverse the leads to one loudspeaker. The PHASE switch is used to correct phase in the source material whenever necessary. ADJUSTING FOR SPECIAL EFFECTS HF FILTER If you wish to reproduce badly worn records, you can minimize the surface noise by switching the HF filter to the FILTER position.
(See page 15 ADJUSTING FOR SPECIAL EFFECTS.) 5. Set the LF filter switch to FLAT. (See page 15 ADJUSTING FOR SPECIAL EFFECTS.) 6. Set the LOUDNESS switch to NORMAL. (See page 15 ADJUSTING FOR SPECIAL EFFECTS.) 7. Set the TAPE switch to NORMAL. 8. Set the BASS CONTROLS and TREBLE CONTROLS so that the indicators are centered between the panel markings L and R. (See page 15 BASS and TREBLE CONTROLS.) 9. Adjust the VOLUME control to the desired volume. 10. Adjust the BALANCE control if necessary.
as for TAPE input. 1. Set the TAPE MONITOR switch to MONITOR. 2. Turn the MODE SELECTOR switch to MONO (L+R). 3. Set the HF cutoff filter switch to FLAT. (See page 15 ADJUSTING FOR SPECIAL EFFECTS.) 4. Set the LF filter switch to FLAT. (See page 15 ADJUSTING FOR SPECIAL EFFECTS.) 5. Set the LOUDNESS switch to FLAT. (See page 15 ADJUSTING FOR SPECIAL EFFECTS.) 6. Set the BASS CONTROLS and TREBLE CONTROLS so that the dial indicators are centered between the panel markings Land R. 7.
BASS AND TREBLE CONTROL RESPONSE 20 RESPONSE IN DB 10 0 -10 -20 20 100 1KC 10KC 20KC FREQUENCY RUMBLE AND HIGH FREQUENCY FILTERS 0 RESPONSE IN OB -5 -10 -15 -20 -25 -30 20 100 1KC FREQUENCY 18 10KC 20KC
LOUDNESS CONTROL 20 15 RESPONSE IN DB 10 5 0 -5 -10 -15 -20 20 100 1KC 10KC 20KC 10 KC 2 0 KC FREQUENCY EQUALIZATION CURVES 25 20 15 RESPONSE IN DB 10 5 0 -5 -10 -15 -20 -25 20 100 1KC FREQUENCY 19
Your Mclntosh MA230 tuner will give you many years of pleasant and satisfactory performance. If you have any questions concerning the operation or maintenance of this tuner please contact: Customer Service Mclntosh Laboratory Inc. 2 Chambers Street Binghamton, New York Our telephone number is 723-5491. The direct dial area code is 607. GUARANTEE Mclntosh Laboratory Incorporated guarantees this equipment to perform as advertised.
LABORATORY INC. 2 CHAMBERS STREET, BINGHAMTON, N. Y. Mods in U.S.A.
