Marantz 8 B Owners Manual

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Model 83 Stereoplronic

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INSTRUCTION MANUAL

The Marantz Model 8 Stereophonic Power Amplifier consists of two completely separate
power amplifiers on one chassis with one common power supply.

WARRANTY:

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eaebunitthatleaveaouplant.Foryourprotectim.itismestimpomntthatyoupropedyfillinthiseardand
returnit promptly alter purchase. Should you netflnd thisurd enclosed. it is the responsibility ofthedealer. from
wbemywptuebasedthemmwpplythiseardtoyou.

OPHATING LINE VOLTAGE:

117 Volts. 50-60 cycles (for A.(:. operation only). All specifications are based on this voltage.
'Iltc usable range is I05 - 125 volts.

"Am OF AMPUFIH:
Ferventiladngpurposenithadvinbletobeatetheampliflercbauiuoasteprovideairbwaroundallmiaeea.

NM CONNECTIONS:

The aboderd 'iNPUT' jacks are recommended for most uses. At these connections subsonic filter: sell ed ire-
queneiea below 20 cycles so as to supprw speaker 'breathing" and otbu subsonic disturbances. A 1.3 volt signal
will drive each amplifier to its full output.

vIllc'"l'l".5'l'" lnpuu bypurla iltc subsonic filler. carrying the low lrcquency response flat to below 2 cycles,
and have the some input sensitivity as the "INPUT connections.

OUTPUT CONNECTIONS:

Use'OOM' (Cmmnmmm)mampflflaoutputmmhdnfipmubuwidadaewndhghnpedamhp
whichtnatcheaeeclupealterlmpedame.

Formaximum efleimcyandloweatdbtortiothlrgoaenlly advisabletomabh dictated maker impedance with
dredosestdedgmbedontputimpedaneetermimlsontheamplifier.ie.:

lOorISObmspenlrertoAmpJOohmtap Bohmspealtertosobmtap 4or30hmrpeaherto4dimtap

The correct amplifier output impedance (or multiple speakers connecting to either one of the amplifier: should
be chosen alter determining the total speaker impedance of all speakers combined (either in parallel or series

eonnection).i.e.:
twoleolarnspeakeninpanlleI-Bohmtap twosdunlpealtersinaeriea ~loolxmtap
twosdmspealtminpanllel- 4oluntap Molohmspealoersiuseries -Sobmtap

Other weaker impedance totals reuniting somewhere between the available amplifier lmpedame speakers should
be connected to the closest impedance value.

When in doubt. it is always prefemble to connect a speaker of an in-between impedance rating to a lunar. rather
tlunhighermmpliflerimpedame tap. Whenrnatehed toured: lemerampliflatape, somelosstnpowereapabillty
will occur. but this is harmless. it speaker is wired to a hidier amplifier tap. distortion can Milt.

To obhin other damping factors, see Wm under INSTALLATION OF OTHER DAMPINC FACTORS.

Mm. TESTS AND ADJUSTMBlTS:

Each amplifier is carefully adjusted at the factory for proper operation. Nevertheleu. the owner should cheek the
operating condition: after 15 minutes when first plead in service and spin after the tube: have "aged." perhaps
12 Items. fleshed: every few months.

The test and adjustment section of the amplifier is comprised of the following:
A. AnaocuratemetercalibntedmindieatetbepropersomilihmpemBIASeunditioneneadutube.

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B. BIAS screwdriver adjustments situated next to each corresponding output tube which are protected from
accidental shiltlng of calibration by black plastic screw-on cops. These should be removed beion
warming up for test to avoid burning hands on hot tubes.

C. A test switch having [our test positions. two above and two below. with spring return to normal (playing
position). The best positions correspond to thc meter tending: and adjustments listed in A and 5 above.

TEST PROCEDURE:

Before mdting these tests be sure to turn the preamp volume control fully down.

A. Move the Test Switch to the Al test position. The meter pointer will swing to the right. indicating
the current drawn by tube ELM/OCA7 designated Al. Turn the corresponding adjustment carefully
with a screwdriver until the meter wading is on the BIAS line. (This reading will normnlly vary
slightly with line voltage Ind during warrnup. in installation. the BIAS may have to be reset. A current
setting much in excess of the BIAS" marlt will tend to decrease tube life.)

3. Repeat the sun: test and adjustment Ior Inch oi the other positions. being uretol to set exactly to
the same point.

C. It may be necessary to repeat all tests because of slight interaction of adjustments. inability to obtain
satisfactory adjustments usually indicates faulty output tubs»

PARALLB. OPHATION:

Thirdualomplifiermn beeperaledasa ringieampitfier with twice thepoweroutplu. However, there will notbe
an equivalent 18 ohm output top.

To l the two amplifiers. both the inputs and the outputs must be connected in parallel. Use either aterml
cob or interml connection across the input jacks. Be sure to connect the two output impedance taps selected
with good low resistance wire.

Connecting the two "18" tops will produce an 8 ohm output impedance; the two '3 taps - 4 ohms; and the two
4' taps - 2 ohms equivalent output impedance. Do not connect dissimilar output taps together.

LOUDSPEAKH CONNECTION AND PLACEMENT:

Ordinary 18 gauge lamp cord may be used for connection between an amplifier and loudspeaker II the distance is
short. If more than 25 or 30 {out is required. it would be advisable to use a heavier gauge to reduce power losses
and damping factor deterioration.
'lhasing of two loudspeakers will be made easier if each lead wire-con be coded for identification. One wire in
each pair can be coded at both ends with a knot. tape or other device. The coded wires can be used for identical
connections. As an example. the coded wires my be connected between the "common terminals of each speaker
and the common or ground terminals of their amplifiers. The uncodcd wires may then be connected between the
remaining speaker terminals and the recommended impedance tap on the amplifiers. This procedure will normally
insure speaker phasing if the speakers are identical.

Fig] (a
5" ° tru- ASimplephuerevers-alswitchcanbewiredasshowninoneoispakerieadsand
Lx '9" will make phase adjustments euior.

run-nu» / V

Spaker placement cannot be determined by fired nile. Generally. it is better to place speakers symmetrically in
relation to dimers to avoi- ""llfll-"iw, well reflections. For rectangular rooms. speaker placement usually seen-n
best along a short wall.

Spacing between stereo speakers depends entirely upon room size and listening distance. Wider spacing does not
necessarily produce the so-eallctl hole in the middle". A good compromise should be dotemtined by experimt
in order to achieve the most naturalsounding spread. Some esperiment with angling of the speakers may be
rewarding. Sometimes the best eficct can be secured by directing or beaming the sound from both speakers so as
to cros in front of the listening area.

THE FOLLOWING ADJUSTMENTS AND MODIFICATIONS SHOULD BE DONE BY A PRSON
AT LEAST PARTIALLY VERSE!) IN ELECTRONICS:

A.C. WNCE ADJUSTMBtlTS:

There are adiusonents for the AC. balance (drive baknce) at each amplifier lomtod under the chassis directly
in lino with the A2 and 32 controls and accessible by removsl of bottom grille.

Experience has shown little need for rendiusting time settings union a driver tube (OCC'I) is replaced or vastly
diflereat output tubes are installed. These adjustments have been carefully made at the factory prior to shipping.
if it should appear necessary to check the A.C. balance, a variable source of sinrnoidal voltage anywhere from 50
to 1000 cycles is necessary. This should preferably be low in distortion (lea than 1%). although attenuated line
voltage can be used if it hasn't too touch distortion. In addition. use oi a dummy load resistor is preferable (-
resistor approximately equal to one of the output impedance: and upable of temporarily dissipating 35 W.)