PREAMP-AMPLIFIER - sportsbil.comsportsbil.com/mcintosh/Integrated Amp/MA230/MA230_own.pdf · with a tube and transformer power amplifier on the same chassis. The Mclntosh MA230 has

STEREOPREAMP-AMPLIFIER MA230

TABLE OF CONTENTS

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GENERAL DESCRIPTION

TECHNICAL DESCRIPTIONMechanical SpecificationsElectrical Specifications

FRONT PANEL INFORMATION

INSTALLATION

CONNECTIONS

AC ConnectionsGround ConnectionTape Output ConnectionsLoudspeaker ConnectionsAC PowerInput Connections

OPERATING INSTRUCTIONS

GUARANTEE

3-YEAR FACTORY SERVICE CONTRACT

MA

230

MA230 PREAMP-AMPLIFIERGENERAL DESCRIPTION

The new Mclntosh MA230 presents twooutstanding "FIRSTS" for your home stereolistening enjoyment.

. . . The MA230 is the FIRST stereo pre-amp-amplifier on one chassis that meets thetraditional rigorous Mclntosh engineeringperformance standards.

. . . The MA230 is the FIRST stereo instru-ment to combine a solid state preamplifierwith a tube and transformer power amplifieron the same chassis.

The Mclntosh MA230 has eliminated allprevious limitations of single chassis preamp-power amplifiers. The compact design of theMA230 preamplifier allows adequate spaceon the same chassis for a cool running 30watt per channel tube power amplifier. Youcan now enjoy Mclntosh performance andreliability with the convenience of a completesingle chassis stereo instrument.

The dramatic difference in the quality ofmusic reproduction through Mclntosh instru-ments is due directly to low distortion per-

formance. Mclntosh Laboratory is the onlymanufacturer in the entire industry to guar-antee and deliver the lowest distortion at allaudio frequencies.

Long life, flexibility, and highest qualityconstruction are characteristic designs inevery Mclntosh instrument. Wide electricaland thermal margins of safety for all com-ponents, transistors and tubes add to thelong life built into every Mclntosh product.Advanced engineering and cool operating de-sign insure reliability and low maintenancecosts. A Mclntosh instrument is withoutdoubt the most economical and worthwhilelong term investment in the high fidelityindustry.

Once you have enjoyed the outstandingperformance of the MA230, you will under-stand why Mclntosh products have earnedtheir reputation as "THE BEST." Your Mc-lntosh MA230 stereo preamp-amplifier willgive you years of the finest possible per-formance and will become a highly valuedpart of your home music system.

TECHNICAL DESCRIPTION

The new Mclntosh MA230 combines, forthe first time, a Mclntosh engineered stereosolid state preamplifier and tube power am-plifier on the same chassis. Long months ofdiligent research by the Mclntosh engineer-ing staff have produced a compact solid statepreamplifier which meets all the traditionalMclntosh performance standards. The MA-230 solid state preamplifier eliminates thedrawbacks and limitations of all previoussolid state circuits. The compact design ofthis preamplifier has allowed sufficient spaceto properly position a 30 watt per channelstereo tube power amplifier on the samechassis.

The MA230 continues the Mclntosh repu-tation for cool and efficient operation. Carefulchassis planning has permitted the output

tubes to be spaced well apart. This widespacing allows more air circulation aroundthe tubes. Better air circulation means cooleroperation. Cooler operation means longertrouble free life. The large Mclntosh outputand power transformers are positioned acrossthe center of the chassis for mechanicalstability and strength.

The MA230 preamplifier section is de-signed around the latest type Silicon-Planartransistors. Silicon-Planar transistors wereselected because of their high thermal sta-bility, low leakage, low noise, and superiorhigh frequency response. A total of 12 tran-sistors are used. Three transistors are usedin each channel of the phono preamplifiersection. Three transistors are also used in

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each channel of the tone control section. Theentire preamplifier has low noise, low distor-tion, and is not affected by normal roomtemperature variations.

Typical Mclntosh care in design protectsagainst input signal overload. Both the highlevel inputs (Tuner, Tape and Aux) and thelow level phono and tape head inputs canaccept much higher than average input sig-nals without overload.

For example, at 2000 cycles the phonoinputs can-accept 150 millivolts of signal be-fore overload. No magnetic phono cartridgenow available is capable of even one half thisoutput voltage.

PREAMPLIFIEREach channel of the Phono preamplifier

section uses 3 transistors. The first inputstage is a high gain amplifier. The output ofthis transistor feeds a pair of transistors con-nected in a Darlington configuration. A nega-tive feedback loop connects from the outputof the Darlington pair back to the emitter ofthe first stage transistor. This feedback loopreduces noise and distortion and also pro-vides accurate frequency compensation forphono records and tape head playback. Neg-ative feedback remains in effect even at 20cycles where gain is highest, to insure lowdistortion over the entire frequency range.

The phono input impedance is 47,000ohms to match most magnetic phono car-tridges. Other resistors may be added tomatch the occasional cartridge which re-quires a different input impedance.

The Tape Head input impedance is slightlyover 1 megohm for uniform high frequencyresponse with typical tape playback heads.

The Tape Outputs come directly from theSelector Switch and provide signal level suffi-cient for feeding a tape recorder. For ex-ample, 10 millivolts of signal at the phonoinput results in 1.6 volts at the Tape Output.

The high level inputs feed through theBalance and Volume controls into a transistorconnected as an Emitter-Follower. This tran-sistor is the first stage of the Tone Controlsection. The impedance of the high levelinputs is 250,000 ohms. Any conventional

tuner or tape recorder may be connected tothe MA230 without loss of low frequencies.The emitter-follower provides the requiredhigh input impedance and low output im-pedance for feeding the tone control negativefeedback circuits. The last two stages of thetone control section are two transistors in aDarlington configuration similar to the phonopreamplifier. The high gain of these stagesis used to advantage for the tone controlnegative feedback circuits. This type of cir-cuit assures low distortion and the correctshape for the tone control response curves.Negative feedback is maintained at all fre-quencies, even with the tone controls turnedto full boost. Distortion is, therefore, keptvery low, even at the frequencies wheremaximum boost occurs. The total distortionof the entire MA230 preamplifier circuit isactually only a few hundredths of 1 percent.

POWER AMPLIFIERThe output of the solid state preamplifier

feeds into one half of a 12AX7 dual triodetube. The two triode sections of the 12AX7are the first stage voltage amplifiers in eachchannel of the power amplifier. The output ofeach 12AX7 is direct-coupled to a 12AU7tube used as a grounded-grid inverter-driver.The balanced output voltages of the grounded-grid inverter are precisely maintained inamplitude over the entire audio frequencyrange. The inverter output balance is con-trolled by precise plate load resistors. Anadjusting control is also included in the in-verter plate circuit to insure exact signal bal-ance and minimum low frequency distortion.This control is factory set using a distortionanalyzer. Normally, the mid point setting ofthis control is adequate to keep overall dis-tortion less than ½ of 1% at full output.

The outputs of the 12AU7 tubes are cou-pled through mylar-insulated capacitors tothe output tube grids. These capacitors arethe only coupling capacitors used in thepower amplifier circuit, which keeps phaseshift very low at low frequencies.

The 7591 output tube plates are coupledto the speaker through a special Mclntoshengineered output transformer. A separatetertiary winding on the transformer also

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couples the output tube cathodes into thetransformer. Six db of negative feedback isproduced in the output stage with this circuit.

Twenty db of negative feedback aroundthe entire power amplifier circuit is achievedby coupling a special secondary winding onthe output transformer back to the first stage12AX7 cathode.

The fixed bias on the 7591 output tubesis adjustable over a small range with indi-vidual controls. These adjustments are fac-tory set to 0.7 volts DC at the test points.Convenient test point jacks are provided nextto each output tube. The setting of these con-trols is not critical and need not be touchedin normal use. To assure best possible per-formance of the MA230 over long periods ofoperation, or whenever output tubes arechanged, the bias can be checked and resetif necessary.

A pair of stereo headphone jacks is pro-vided on the front panel. The jacks are con-nected to the amplifier outputs through 100ohm resistors for low impedance head phones.The speaker switch turns off the speakersfor headphone listening.

POWER SUPPLYA silicon rectifier voltage doubler power

supply assures stable voltages and cool oper-ation. A zener diode holds the transistor pre-amplifier operating voltages at exact valuesand eliminates all traces of hum.

A thermistor is used in the primary ACcircuit of the power transformer to protectagainst line voltage surges and extend tubeand transistor life. The thermistor placesslightly more than 25 ohms in the AC circuitwhen cold. As the amplifier warms up thethermistor also warms and its resistancethen drops to less than 0.7 ohm. The ampli-fier then operates at normal line voltages butis protected during the initial warmup period.Again, Mclntosh care in engineering protectsyour investment in listening pleasure.

The combination of these features resultsin performance available only from a Mc-lntosh amplifier. The MA230 delivers 30watts RMS continuous power from bothchannels at the same time, 20 cycles through20,000 cycles with harmonic distortion lessthan ½ of 1%. This superior level of per-formance is unequaled by any other preamp-amplifier. A listening test quickly proves thesuperiority of the Mclntosh MA230.

MECHANICAL SPECIFICATIONS

SizeFront panel, 16 inches wide by 57/16 incheshigh; chassis, 15 inches wide by 4½ incheshigh by 14½ inches deep, including connec-tors. Clearance in front of mounting panelincluding knobs, 1½ inches.

Weight43 pounds net, 57 pounds in shipping carton.

FinishAnodized gold and black (Front Panel).

ELECTRICAL SPECIFICATIONS

Power Output30 watts continuous per channel with bothchannels operating simultaneously. 60 wattscontinuous, monophonic.

Harmonic DistortionLess than 0.5% at 30 watts output, 20 cyclesthrough 20,000 cycles. Distortion decreasesas power output is reduced.

Intermodulation DistortionLess than 0.5% for any combination of fre-quencies from 20 cycles through 20,000cycles if instantaneous peak power is 60watts per channel or less.

Phase Shift, Power Amplifier-Less than ± 5° 20 to 20,000 cycles.

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Frequency RangeAt 30 watts output both channels.

+ 0, -0.5db 20 cycles through 20,000cycles.+0, -3db 15 cycles through 70,000cycles.

Output Impedance4 ohms, 8 ohms, 16 ohms.

Internal Impedance/DampingLess than 10% of rated load impedance;damping factory of 10.

Input Sensitivity and ImpedanceAuxiliary, Tape, Tuner, and Tape Monitor:.25 volts, 250K ohms.Phono 1 and Phono 2: 1.5 millivolts, 47,000ohms.Tape Head: 1.5 millivolts, 1 Megohm.

Total Noise (including Power Amplifier)High level inputs: 75db below rated output.Low level inputs: 60db below rated output;less than 4.0 microvolts at input terminals.

Tape Output.25 volts into 25,000 ohms with rated input;1.6 volts with 10 millivolts at Phono input.

Left Plus Right Output10 volts from generator impedance of 5,000ohms.

Bass Controls±18db at 20 cycles, with friction clutch forindependent adjustment of each channel.

Treble Controls± 18db at 20,000 cycles, with friction clutchfor independent adjustment of each channel.

Comp (Compensator) SwitchRIAA or LP phono equalization.

Tape SwitchNormal or Tape Monitor.

Phase SwitchNormal (0°) or reverse (180°).

Speaker SwitchSpeakers ON, or OFF for headphone listening.

HF FilterFlat, or 5,000 cycle cutoff, 12db per octave.

LF FilterFlat, or 50 cycle cutoff, 12db per octave.

Loudness SwitchNormal or compensated bass and treble.

Headphone JacksTwo, for two pairs of headphones.

Input Selector6 positions: AUX, TAPE, TUNER, PHONO 1,PHONO 2, TAPE HD.

Mode Selector7 positions: L to L and R, R to L and R,STEREO REVERSE, STEREO, MONO (L+R),L+R to L, L+R to R.

Transistor Complement (Preamplifier)8-2N2926 Silicon Planar4-11BQ101 Silicon Planar

Tube Complement (Power Amplifier)4-7591 Power Output2-12AU7 Driver/Phase Inverter1-12AX7 1st Audio Voltage Amplifier

Power Requirements120-125 volts AC, 60 cycles. 150 watts atzero signal output; 210 watts at rated output.

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FRONT PANEL INFORMATION

INPUT SELECTOR

Figure 1. MA230 Front Panel.

Select any of six program sources with theMA230 INPUT SELECTOR switch.

1. AUX: Use the AUX position for anyauxiliary program source requiring flat ampli-fication, such as a tuner or television sound,connected to the back panel AUX input jacks.

2. TAPE: Use the TAPE position for a self-contained tape recorder (tape recorder hav-ing its own playback preamplifier), connectedto the back panel TAPE input jacks.

3. TUNER: Use the TUNER position forany AM, FM, or FM stereo tuner connected tothe back panel TUNER input jacks.

4. PHONO 1: Use the PHONO 1 positionfor any magnetic phono cartridge connectedto the back panel PHONO 1 input jacks.

5. PHONO 2: Same as PHONO 1. (For ex-ample, PHONO 1 can be connected to arecord changer while PHONO 2 is connectedto a manual turntable.)

6. TAPE HD: Use the TAPE HD (TapeHead) position for a tape deck that does nothave its own playback preamplifier. The TapeHead leads are connected to the back panelTAPE HD input jacks.

MODE SELECTOR

Use the MODE SELECTOR to:Listen to normal stereo (see 4 following

and page 15);Reverse the left and right arrangement of

musical instruments (see 3 following andpage 15).

Balance the amplifiers and loudspeakersin a stereo system (see 6 and 7 following andpage 15).

Listen to monophonic sound (see 1 and 2following and page 15).

Listen through both loudspeakers toeither channel of a stereo program source(see 1 and 2 following and page 15).

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Figure 2. INPUT SELECTOR Switch.

Figure 3. MODE SELECTOR Switch.

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 tothe "left" loudspeaker and the "right" inputto the "right" loudspeaker.

5. MONO (L+R): adds the "left" inputand the "right" input and then connects theL + R program to both amplifiers and loud-speakers.

6. L + R TO L: connects both left and rightinputs to the "left" loudspeaker only.

7. L+ R TO R: connects both left and rightinputs to the "right" loudspeaker only.

VOLUME

Use the MA230 VOLUME control to regu-late the volume level of both channels. Turn-ing the VOLUME control clockwise increasesvolume level.

BALANCE

Use the MA230 BALANCE control to bal-ance unequal volume in the left and rightchannels of a program source. The volumeof each speaker system relative to the othercan be varied, at the same time the combinedroom volume level is not changed.

LEFT . . . turning the control to the leftaccents the left channel by reducing the rightchannel output.

RIGHT . . . turning the control to the rightaccents the right channel by reducing theleft channel output.

BASS

Figure 5. BALANCE Control.

The BASS control is a dual-concentriccontrol. The two are friction coupled. Thecenter knob controls the left channel. Theouter ring controls the right channel. With theBASS control it is possible to vary the bassloudness relationship existing between theleft and right speakers. Both controls can be,turned together as a single adjustment or onemay be held as the other is turned. Clockwiserotation increases bass loudness; counter-clockwise rotation decreases bass loudness.

TREBLEThe TREBLE control is dual-concentric

control. The two are friction-coupled. Thecenter knob controls the left channel. Theouter ring controls the right channel. Withthis control it is possible to vary the treblerelationship existing between left and rightspeakers. Both controls can be turned to-gether as a single adjustment or one may beheld as the other is turned. Clockwise rota-tion increases treble loudness; counterclock-wise rotation decreases treble loudness.

Figure 6. BASS Control.

Figure 4. VOLUME Control.

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Figure 7. TREBLE Control.

COMP (Compensation)

Use the COMP switch to correct for phonoequalization introduced by the recordingprocess. The recording industry has agreedto record all current LP and stereo recordingswith RIAA equalization. On earlier stereo andon mono recordings use the position thatsounds best to you.

The MA230 TAPE switch makes it possibleto instantaneously compare recorded ma-terial with the source signal. Use the MA230TAPE switch to know instantaneously, as youare recording, that the music on the tape isacceptable. Tape monitor jacks on the backpanel accept a signal from a tape recorderwith a monitor head and preamplifier.

NORMAL . . . the original program sourceis fed through the power amplifiers and theloudspeakers.

MONITOR . . . the recorded sound on thetape is fed through the power amplifiers andspeakers.

The PHASE switch corrects for loud-speaker or program phasing. When thisswitch is in the 180° position the phase in theleft channel is reversed.

Figure 9. TAPE Switch.

The loudspeakers are turned off when theSPEAKER switch is in the OFF position, toallow listening through headphones. Theheadphone jacks are on at all times.

Figure 8. COMP (Compensation) Switch.

TAPE

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Figure 11. SPEAKER Switch.

SPEAKER

Figure 10. PHASE Switch.

PHASE

LF (Low Frequency Filter) LOUDNESS

Use the LF filter to reduce low frequencynoises created by a turntable, record changer,or vibration acoustically coupled to the phonoplayer from the speakers.

FLAT.. .filter disconnected; flat response.FILTER . . . low frequencies reduced

sharply below 50 cycles.

When you turn down the volume, musicseems to lose much of its bass and some ofits treble. This effect is due to the sensitivitycharacteristics of human hearing. The re-sponse of the human ear to bass and treblepitch decreases more rapidly than its re-sponse to the mid-tonal range. The LOUD-NESS switch automatically provides the cor-rect amount of bass and treble boost re-quired to compensate for this change inresponse of the human ear at low loudnesslevels. Use the LOUDNESS switch in theCOMPENSATED position to listen at lowvolume and still hear full frequency range.

HEADPHONE

S P E A K E RON

POWERON

HEAD PHONE HEAD PHONE

OFF OFF

Use the HF filter to minimize surface noisewhen reproducing old or badly worn record-ings.

FLAT... filter disconnected; flat response.FILTER . . . high frequencies reduced

sharply above 5000 cycles.

Two pairs of low impedance stereo head-phones can be connected to the MA230.Both front panel headphone jacks are con-nected to the MA230 output through 100ohm resistors. These resistors provide thecorrect output volume level for headphoneoperation.

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HF (High Frequency Filter)

INSTALLATION

The MA230 can be installed in furniturecabinets, custom built installations or pro-fessional relay racks. If the unit is to be usedon a shelf or table top, it can be housed in anattractive Mclntosh cabinet.

Allow sufficient cabinet space for air circu-lation. Minimum internal cabinet dimensionsshould be at least 16 inches wide, 14 inchesdeep, and 6 inches high. The back of thecabinet should be left as open as possible forventilation. Proper ventilation will insure youramplifier a long and trouble-free life,

The MA230 installs conveniently from thefront of the cabinet into the panel cutout.Two amplifier mounting brackets are pro-vided for each side of the cabinet panel open-ing so the MA230 can slide easily into posi-tion. The mounting brackets are attached tothe cabinet panel by two mounting strips.The mounting strips are attached to the backof the cabinet panel on each side of the panelcutout. With the screws supplied, front cabi-net mounting panels up to one inch thicknessmay be used. Two knurled screws placed intothe MA230 back panel, through the mountingbrackets, hold the unit firmly in place. Due tothe weight of the MA230, it is recommendedthat the mounting brackets rest on a woodenshelf in the cabinet for added support.

The design of the mounting templateallows the cutout to be located either fromthe front or the back of the cabinet panel.Since the MA230 should rest on a shelf, lo-cate the cutout from the back of the panel.

1A. Position the MA230 mounting tem-plate on the cabinet panel area to be cutoutfor the installation.

1B. On the back of the cabinet panel,scribe a vertical line through the exact centerof the cutout area.

Place the template against the back of thepanel. Match the template centerline with thescribed cutout centerline. The bottom of thetemplate must rest on the shelf.

1C. On each side of the centerline of thetemplate there are two holes marked "C."The smaller diameter hole is below the largerdiameter hole. These are the "LOCATINGHOLES." These holes are used to locate thefront panel of the MA230 with reference tothe shelf behind the cabinet panel. So thatthe MA230 will rest on the cabinet shelf, fol-low these instructions carefully.

Mark the back of the cabinet panel with apointed instrument through the two smalldiameter "LOCATING C" holes. Drill thesetwo holes through the cabinet panel with a3/16" diameter drill. Be certain the drill is per-pendicular to the panel.

Now position the template on the front ofthe panel. Align the larger 3/16" diameterupper "LOCATING C" holes in the templatewith the drilled holes in the cabinet panel.

2. Mark the "A" and "B " drill holes andalso the four corner cutouts in the template.Join the corner markers. The edge of thetemplate can be used as a straight edge.

Figure 17. Positioning the Mounting Templateover proposed area to be cutout.

Figure 18. Marking the Cutout Indications.

3. First drill the mounting holes.

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4. Cut out the rectangular opening.

5. Secure the mounting strips to the in-side of the panel.

In the hardware package are 4 flat headscrews and 8 fillister head screws. Two of theflat head screws of the proper length areused to attach the mounting strips to thecabinet panel. Four of the fillister headscrews are used to attach the MA230 mount-ing brackets to the cabinet panel and themounting strips behind the panel. The ¼ inchscrews are used for panel thickness less than3/8 inch. The 1¼ inch screws are used withpanels from 3/8 inch to 1 inch in thickness.

Insert the proper length flat head screwthrough the center " B " holes of the cabinetpanel ("B" holes marked on mounting tem-plate). Position the mounting strip behindthe cabinet panel. The edge of the mountingstrip that has the clips must be facing therectangular cutout. Align the three holes inthe mounting strip with the holes in the cabi-net panel.

Tighten the flat head screw so that thescrew head pulls in the wood panel level withthe panel surface. Repeat this with the sec-ond mounting strip on the other side of therectangular cutout.

6. Left and right metal mounting bracketsare packed with the MA230. Fasten these twomounting brackets to the cabinet panel usingfour of the fillister head screws. These screwsshould pass through the mounting shelfflange, through the cabinet panel and theninto the mounting strip attached to the insideof the panel. Tighten the screws firmly, butdo not over-tighten.

7. Prepare the MA230 for mounting byremoving the four plastic feet fastened underthe chassis.

8. The MA230 is installed from the FRONTof the cabinet. Insert the MA230 power cordthrough the rectangular opening of the cabi-net panel. Carefully slide the MA230 into theopening so the plastic rails on the bottom ofthe chassis engage the grooves in the metalmounting brackets. Slide the MA230 in untilits front panel is against the cabinet mount-ing panel.

9. Secure the MA230 to the mountingbrackets by inserting the two knurled screwsinto the back of the MA230 chassis, throughthe back flanges of the mounting brackets.

Figure 21. Mounting Brackets installed in cabinet panel. Figure 22. Securing MA230 to Mounting Brackets.

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Figure 20. Securing Mounting Stripsto Installation Cutout.

Figure 19. Installation Cutout.

CONNECTING

AC CONNECTIONS

There are three AC outlets on the backpanel of the MA230. The black receptacleshave a maximum power rating of 350 wattstotal. The power to the two black receptaclesis controlled by the front panel power switch.Use these receptacles for accessories suchas a tuner and tape recorder. The red recep-tacle is not switched. Use the red recep-tacle for powering a turntable or record

changer. The red receptacle is not switchedto prevent turning off the power to the turn-table while its idler drive is still engaged. Theturntable is protected by this arrangementbecause it is necessary to turn off the turn-table with its own control switch. The turn-table drives will then be properly disengagedto avoid possible damage.

Figure 23. AC CONNECTIONS

L+R OUTPUT

Both left and right channel amplifier out-puts are combined into a monophonic signalat the L+R output jack. Connect this jack toan external amplifier for monophonic repro-duction through another speaker system.Monophonic signals can then be distributedto other rooms without affecting the normalstereo performance of the MA230.

GROUND CONNECTIONS

A single ground post is provided on theMA230. The chassis ground from turntables,record changers, tape decks, etc., should beconnected to this post. Do not connect otherground wires to the same units. Hum islikely to be heard in the system if more thanone ground circuit is used.

The left and right cables from each pro-

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gram source should be twisted together andthe ground wire from each source can bewound or twisted in with these cables. Toavoid hum, make sure the ground wire doesnot make any connections to shields of theleft and right channel cables except for theconnection provided with the MA230 groundpost.

TAPE OUTPUT CONNECTIONSThe TAPE OUTPUTS on the back panel

provide the program material with sufficientlevel for feeding a tape deck or recorder. TheTAPE OUTPUT signal is not affected bythese front panel controls: VOLUME, BASS,TREBLE, BALANCE, LOUDNESS, PHASE,TAPE, MODE SELECTOR, SPEAKER, LF andHF FILTERS. The INPUT SELECTOR and theCOMP switch (in Phono 1 and Phono 2) affectthe TAPE OUTPUTS. All recording volumeadjustments are made at the tape recorder.The room listening volume of the MA230 can

then be set at any desired level withoutaffecting recording volume.

LEFT and RIGHT SPEAKER OUTPUTSpeaker systems of 4, 8, or 16 ohms im-

pedance connect to the SPEAKER terminalson the back panel of the MA230.

Select the output impedance desired byplacing the wire pigtail with the lug under theappropriate impedance screw on each chan-nel. Tighten the screws firmly. Connect theleft speaker leads to the two screws underthe lettering marked LEFT SPEAKER. Con-nect the right speaker leads to the two screwsunder the lettering marked RIGHT SPEAKER.The common or chassis ground tap on eachchannel is marked C. Connect each speakerin an identical manner.

AC POWERPlug the AC power cord into a 120-125

volt, 50 or 60 cycle power line.

INPUT CONNECTIONS

The MA230 provides seven separate pro-gram inputs controlled by the INPUT SELEC-

TOR switch. The input for tape monitor iscontrolled by the TAPE switch.

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CONNECTION

TAPE MONITOR

AUX

TAPE

TUNER

CONNECTION

PHONO 1 & 2

TAPE HEAD

FUNCTION

The tape monitor input accepts a signal from a taperecorder with a monitor head and preamplifier

The auxiliary input accepts any auxiliary service requir-ing flat frequency response, such as a T.V. set, tuner,tape recorder with its own playback preamplifier, etc.

The tape input operates with tape machines containingtheir own playback preamplifier

The tuner inputs accept AM and FM outputs from astereo tuner or a pair of stereo tuners or the multiplexoutput of an adapter of multiplex tuner

FUNCTION

These jacks are to be used with magnetic cartridges,..

These jacks are to be used with a tape deck that doesnot contain its own playback preamplifier

INPUTSENSITIVITY

0.25 V

0.25 V

0.25 V

0.25 V

INPUTSENSITIVITY

1.5 MV

1.5 MV

INPUTIMPEDANCE

250K

250K

250K

250K

INPUTIMPEDANCE

47K

1 megohm

DIRECTIONALFM ANTENNA

ROTATOR

8 OHM SPEAKERS SHOWN

TO 12OVAC OUTLET

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GROUND

If a phono cartridge requires less than47,000 ohms load impedance, a resistor canbe added across the terminals of the car-

tridge to achieve the correct termination.The following chart may be used as a guide:

Desired Impedance

47,000 ohms (47K)37,000 ohms (37K)27,000 ohms (27K)15,000 ohms (15K)6,800 ohms (6.8K)

Resistor Across Input

No Resistor180,000 ohms (180K)62,000 ohms (62K)22,000 ohms (22K)8,200 ohms (8.2K)

OPERATING INSTRUCTIONS

BALANCING A STEREO SYSTEMThe performance and enjoyment of a

stereo system is greatly increased when thesystem is properly balanced. The balance ofa stereo system is affected by many thingsincluding room acoustics, furniture place-ment, room shape, small differences in loud-speakers, and unequal program loudness.

The control marked BALANCE on theMA230 can be used to perfectly balance allfactors for best listening.

1. Play a familiar recording on the recordplayer.

2. Turn the INPUT SELECTOR to thePHONO position into which the record playeris connected.

3. Turn the BASS and TREBLE controlsso that the knob indicators are centered be-tween the panel markings L and R.

4. Turn the BALANCE control to the cen-ter or 12 o'clock position.

5. Place the LOUDNESS switch in theNORMAL position.

6. Place the TAPE switch in the NORMALposition.

7. Place the PHASE switch in the 0°position.

8. Place the LF filter switch in the FLATposition.

9. Place the HF filter switch in the FLATposition.

10. Turn the MODE SELECTOR to theL+R to L position.

11. While the program is playing, alter-nate the MODE SELECTOR between the L+Rto R and the L+R to L positions. Adjust theMA230 BALANCE control until the loud-speaker volumes are equal.

The stereo system will now be balanced.Different program material such as records,tapes or FM broadcasts may require differentBALANCE control settings. It is not at all un-usual for the BALANCE control to remain offcenter one way or the other for correct bal-ance. This means the BALANCE control isperforming the function it was designed for.

ADJUSTING PHASE1. Set the MODE SELECTOR to STEREO.2. Turn the BASS controls and TREBLE

controls to straight up position with the dialindicators centered between the panel mark-ings L and R.

3. Stand approximately 10 feet in front ofand midway between the loudspeakers. The

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source of sound should appear to be directlyin front of you. Alternate the PHASE switchbetween 0° and 180°. If the sound is not di-rectly in front of you in the 0° position, re-verse the leads to one loudspeaker. ThePHASE switch is used to correct phase in thesource material whenever necessary.

ADJUSTING FOR SPECIAL EFFECTSHF FILTER

If you wish to reproduce badly wornrecords, you can minimize the surface noiseby switching the HF filter to the FILTER posi-tion.LF FILTER

If you are using a turntable or changerwhich has low-frequency rumble noise, youmay reduce it by pushing the LF filter switchto the FILTER position.

BASS CONTROLS AND TREBLE CONTROLSThe tone balance which you hear when

listening to an orchestra is affected by theconductor's instructions to his musicians,the acoustical environment in which you arelistening, and your own subjective hearinginterpretation. Considering these conditions,it is easy to see why tone balance controlsplay a major role in correcting for the follow-ing factors:

1. Each person's subjective idea of tonebalance.

2. Loudspeaker frequency response char-acteristics.

3. Loudspeaker placement in the listen-ing room.

4. The conductor's idea of tone balanceat the time the recording was made.

5. The microphone frequency responsecharacteristics.

6. The recording process influences.These factors can be considered as en-

vironmental influences. The BASS CON-TROLS and TREBLE CONTROLS provide adegree of compensation for effects of en-vironment. Listen to your system with eachcontrol set with the indicators centered be-tween the panel markings L and R. If youwish to reduce treble in relation to bass forexample, turn the TREBLE CONTROLS coun-terclockwise until the tone balance soundscorrect to you. These controls will modify

tone balance without introducing any unde-sirable effects. Do not be surprised if youfind your preference in tone changing fromtime to time.

PHASEIf the stereo sound seems to come from

either side of the room instead of being dis-tributed between the loudspeakers, turn thePHASE switch to 180°. This listening effectis due to reproducing sound that is out ofphase from one channel to the other. Youwill find some records and tapes may differfrom others in this respect.

LISTENING TO A STEREO TUNER1. Turn the INPUT SELECTOR to TUNER.2. Turn the MODE SELECTOR to STEREO.3. Set the PHASE switch to 0°.4. Set the HF cutoff filter switch to FLAT.

(See page 15 ADJUSTING FOR SPECIALEFFECTS.)

5. Set the LF filter switch to FLAT. (Seepage 15 ADJUSTING FOR SPECIAL EFFECTS.)

6. Set the LOUDNESS switch to NORMAL.(See page 15 ADJUSTING FOR SPECIALEFFECTS.)

7. Turn the BASS CONTROLS and TREBLECONTROLS so that the indicators are cen-tered between the panel markings L and R.(See page 15 BASS AND TREBLE CON-TROLS.)

8. Set the TAPE switch to NORMAL.9. Adjust the VOLUME control to the de-

sired volume.10. Adjust the BALANCE control if neces-

sary.After a warm up of about 30 seconds, turn

the tuning knob on your tuner to find thestation of your choice.

LISTENING TO A STEREO RECORDTo listen to stereo records, proceed as

follows:1. Turn the INPUT SELECTOR to PHONO

1 or PHONO 2, whichever is connected to thecartridge you wish to hear.

2. Set the MODE SELECTOR to STEREO.3. Set the PHASE switch to 0°.4. Set the HF cutoff filter switch to FLAT.

15


5. Set the LF filter switch to FLAT. (Seepage 15 ADJUSTING FOR SPECIAL EF-FECTS.)


7. Set the TAPE switch to NORMAL.8. Set the BASS CONTROLS and TREBLE

CONTROLS so that the indicators are cen-tered between the panel markings L and R.(See page 15 BASS and TREBLE CON-TROLS.)

9. Adjust the VOLUME control to the de-sired volume.

10. Adjust the BALANCE control if neces-sary.

LISTENING TO MONOPHONIC RECORDSTo listen to monophonic records, proceed

as follows:1. Turn the INPUT SELECTOR to PHONO

1 or PHONO 2, whichever is connected to thecartridge you wish to hear.

2. Turn the MODE SELECTOR to MONO(L+R).

3. Set the PHASE switch to 0°.4. Set the HF cutoff filter switch to FLAT.




7. Set the BASS CONTROLS and TREBLECONTROLS so that the indicators are cen-tered between the panel markings L and R.(See page 15 BASS AND TREBLE CON-TROLS.)



LISTENING TO TAPE DECKSTo listen to tape from a tape deck, proceed

as follows:1. Turn the INPUT SELECTOR to TAPE

HEAD.

2. Turn the MODE SELECTOR to MONO(L+R) or STEREO, depending on the pro-gram on the tape.





7. Set the BASS CONTROLS and TREBLECONTROLS so that the dial indicators arecentered between the panel markings L and R.

8. Adjust the VOLUME control to thedesired volume.


LISTENING TO A STEREO TAPE MACHINEA stereo tape machine with its own play-

back preamplifiers should be plugged intothe AUX input or the TAPE MONITOR i n p u t -not the TAPE HEAD input.

If the TAPE input is used, proceed asfollows:

1. Turn the INPUT SELECTOR to TAPE.2. Turn the MODE SELECTOR to MONO,

(L+R) or STEREO depending on the programon the tape.





7. Set the BASS CONTROLS and TREBLECONTROLS so that the dial indicators arecentered between the panel markings Land R.



If the AUX input is used, turn the INPUTSELECTOR to AUX; then, proceed the same

16

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.



5. Set the LOUDNESS switch to FLAT.(See page 15 ADJUSTING FOR SPECIALEFFECTS.)

6. Set the BASS CONTROLS and TREBLECONTROLS so that the dial indicators arecentered between the panel markings Land R.



POWERThe POWER ON-OFF switch controls the

AC power to the MA230 and the two black ACreceptacles on the back panel. The red ACreceptacle is not switched, and is on at alltimes.

HEADPHONETwo pairs of low impedance stereo head-

phones can be connected to the MA230.Both front panel headphone jacks are con-nected to the MA230 output through 100ohm resistors. These resistors provide thecorrect output volume level for headphoneoperation.

ADJUSTMENTS

Two simple circuit adjustments are in-cluded in the MA230. After extensive use orwhen tubes have been replaced, these ad-justments will insure top performance fromyour MA230.

The DC bias of each 7591 output tube canbe individually set. Test Point jacks and biasadjust controls are conveniently mounted onthe chassis next to each output tube. Theoutput tubes, Test Point jacks, and bias con-trols are marked V, TP, and R, respectively.The bias adjust control can be reached fromthe top of the chassis with a small screw-driver. Set the Bias controls for a DC voltageof 0.7 volts from each Test Point jack tochassis ground. Use a VTVM or sensitive DC

voltmeter. Check all voltages a second timeand readjust the controls if necessary.

A phase inverter AC signal balance controlis provided on each amplifier channel. Thesecontrols are factory set with a harmonic dis-tortion analyzer for minimum distortion at 20cycles at 30 watts output. Normally just amidpoint setting of these controls is ade-quate to keep overall distortion to less than0.5% at full output. If the necessary distor-tion measuring equipment is available, seteach control for minimum harmonic distor-tion at 20 cycles at 30 watts output. Balancecontrol R4 adjusts the left channel signalbalance, and R5 the right channel balance.

17

RE

SP

ON

SE

IN

D

B

20

10

0

-10

-20

20 100 1KC 10KC 20KC

0

-5

-10

-15

-20

-25

-30

18

BASS AND TREBLE CONTROL RESPONSE

FREQUENCY

RUMBLE AND HIGH FREQUENCY FILTERS

RE

SP

ON

SE

IN

O

B

20 100 1KC 10KC 20KC

FREQUENCY

LOUDNESS CONTROL

FREQUENCY

EQUALIZATION CURVES

25

20

15

10

5

0

- 5

-10

-15

-20

-25

20 100 1KC 10 KC 20 KC

FREQUENCY

19

20

15

10

5

0

- 5

-10

-15

- 2 0

RESPONSE IN DB

RESPONSE IN DB

20KC10KC1KC10020

Your Mclntosh MA230 tuner will give you many years of pleasantand satisfactory performance. If you have any questions concern-ing the operation or maintenance of this tuner please contact:

Customer ServiceMclntosh Laboratory Inc.2 Chambers StreetBinghamton, New York

Our telephone number is 723-5491.The direct dial area code is 607.

GUARANTEE

Mclntosh Laboratory Incorporated guar- period of 90 days from date of purchase.antees this equipment to perform as adver- This guarantee does not extend to compo-tised. We also guarantee the mechanical and nents damaged by improper use nor does itelectrical workmanship and components of extend to damage incurred during transpor-this equipment to be free of defects for a tation to and from Mclntosh Laboratory, Inc.

3-YEAR FACTORY SERVICE CONTRACT

An application for a FREE 3-YEAR FAC- fined in the 3-year factory service contract.TORY SERVICE CONTRACT is included in the If the application is not mailed to Mclntoshpocket in the back cover of this manual. The Laboratory, only the services offered underFREE 3-YEAR FACTORY SERVICE CONTRACT the standard 90-day guarantee will apply onwill be issued by Mclntosh Laboratory upon this equipment. TAKE ADVANTAGE OF 3receipt of the completely filed out applica- YEARS OF FREE FACTORY SERVICE BYtion form. The term of this contract is de- FILLING IN THE APPLICATION NOW.

In Canada: manufactured under license by:McCurdy Radio Industries, Ltd.22 Front Street WestToronto, Canada

Design subject to change without notice.

LABORATORY INC.

2 CHAMBERS STREET, BINGHAMTON, N. Y.

Mods in U.S.A.

Phone-Area Code 607-723-5491

BE122003AA133-183

PREAMP-AMPLIFIER - sportsbil.comsportsbil.com/mcintosh/Integrated Amp/MA230/MA230_own.pdf · with a tube and transformer power amplifier on the same chassis. The Mclntosh MA230 has

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