McIntosh MA-5100 Owners manual
PRICE $1.25
PREAMPLIFIER-
MA51OO
POWER AMPLIFIER
STEREO
CONTENTS
The Mclntosh "will to perfection" requires that we probe
constantly into the unknown to bring the performance of our
electronic equipment closer to perfection than ever before.
This requires a constant and relentless search for low noise,
broad band conservative design with an ever lower distortion
factor. This is not required of ordinary equipment of average
designs. It is, for us, a costly but worthwhile scientific and
engineering effort. Our continuing research benefits our customers with the almost complete lack of obsolescence and
the most reliable equipment ever made. It also means the
lowest long-range cost to you. Nearly all of the Mclntosh
equipment ever made is still useable, or in use, though it
may have been made twenty years ago.
GENERAL DESCRIPTION
TECHNICAL DESCRIPTION
BLOCK DIAGRAM
PERFORMANCE CHARTS
SPECIFICATIONS
INSTALLATION
IN A HURRY
TYPICAL CONNECTION
CONNECTING
BALANCING
LISTENING
FRONT PANEL CONTROLS
GUARANTEE
2
3-4
5
6
7
8
9
10
11-12
12
13
14-15
16
Your purchase of a Mclntosh instrument
shows that you are a careful discriminat-
ing buyer. One who is interested in quality
performance, quality engineering, quality
manufacturing, and long trouble-free
equipment life. You can protect your investment by spending a few minutes read-
ing this owner's manual.
When you bought a Mclntosh, you bought
countless hours of musical pleasure and
superior performance. Enjoy it!
PREAMPLIFIER-
POWER AMPLIFIER
MA51OO
1
STEREO
GENERAL DESCRIPTION
Conservative claims and specifications are traditional at Mclntosh.
"Rated with honesty and conservatism . . ." "impressive performance figures . . ." "Highest quality of components and construction . . ." are the words used by independent experts when writing
of Mclntosh. To assure you of highest performance every advertised
claim is individually analyzed and verified by engineers using the
most sophisticated and sensitive test instruments. Every unit is individually tested using internationally recognized test procedures. To
assure you of greatest reliability every component part is carefully
tested and evaluated by engineers before it is designed in a Mclntosh.
The MA5100 you have purchased passed more than 100 tests before
it was ready for you. Each connection, wire, resistor, capacitor is
checked and rechecked. All specifications are checked. Mclntosh
testing takes time. The extra investment in thorough testing assures
you of greater musical enjoyment. The performance of your Mclntosh MA 5100 is backed by a money back guarantee. Only Mclntosh
gives you a money back guarantee of performance. Your MA 5100
must be capable of meeting its published specifications or you get
a refund of your purchase price. Mclntosh promises performance.
We either meet our promise or you get your money back.
Your MA 5100 can be protected by a free three year factory service
contract. Take advantage of this service. Fill in the application card
found in the owner's packet. The free three year factory service
contract covers parts and labor. Under the terms of the contract all
parts and labor necessary to repair the MA5100 will be supplied
free of charge. Fill in the service contract application found in the
owner's packet now.
2
TECHNICAL DESCRIPTION
PREAMPLIFIER SECTION
The phono and tape head preamplifier circuits in the MA5100 have
three transistors in each channel. The input selector switch connects
the input jacks to the first voltage gain stage of the preamplifier. The
input stage has high voltage gain and very low noise. The next stage,
an emitter follower, acts as an impedance converter that matches the
input stage to the second voltage amplifier. The emitter follower is
direct coupled to the second voltage amplifier.
Negative feedback is used around the low level section to reduce noise
and distortion to an absolute minimum. The negative feedback also
provides precise frequency compensation for magnetic phono cart-
ridges and tape heads. The feedback remains in effect throughout the
entire audio bandwidth, even at 20 Hz where gain is the highest. This
kind of careful Mclntosh engineering assures you of lowest distortion
performance.
The tape head input impedance is 500,000 ohms. High tape head
input impedance permits uniform high frequency performance from
typical tape transport playback heads.
The MA 5100 is ideal tor tape recording. With an input signal from a
phono cartridge of 10 millivolts, there is 1.4 volts available at the tape
output jacks.
Phono input signal overload is virtually impossible. At 1 KC the phono
input will accept greater than 125 millivolts without overloading. This
is more than 4 times the output from most phono cartridges when
playing a low distortion phonograph record.
The phono input impedance is 47,000 ohms. This matches the imped-
ance of magnetic phono cartridges.
The preamplifier output is connected by the input selector switch to
the tape output, the tape monitor switch, the balance control, and the
first section of the volume control. This arrangement permits recording
of the program without interruption and has the ability to monitor the
recorded tape.
The tone control stages are made up of a three stage amplifier. The
first two transistors are emitter followers. The first emitter follower is
driven from the output of the volume control. The second emitter fol-
lower is direct coupled to the third stage. The third stage is a high
gain voltage amplifier.
Signals pass through the input emitter follower and then couple to the
second and third tone control stages through the tone control network.
The tone control contours are obtained by controlling the large negative feedback around the second and third transistors. This negative
feedback is used to accurately shape the response. The large amount
of negative feedback also makes possible low distortion from the tone
control amplifier.
The output of the tone shaping amplifier drives the low frequency and
high frequency filters and the second section of the volume control.
The filters are designed to remove unwanted noises such as turntable
rumble and record scratch. The filters remove the maximum amount
of objectionable material and still have a minimum effect on the musical content of the program material.
The use of a two section volume control performs two important functions. First, the input section of the volume control increases the signal
handling capability of the tone control amplifier. Use of this arrange-
ment makes overdriving the tone control amplifier almost impossible.
Second, the output volume control assures maximum signal to noise
ratio regardless of the volume control position.
The output of the volume control is fed to a two stage voltage amplifier
that has very low noise characteristics. Negative feedback is used to
improve the signal to noise ratio and assure an absolute minimum of
distortion.
The phase switch is part of the left channel circuitry. The switch
selects from two sources that are "out of phase" to each other.
In the normal position the phase is the same in both channels. When
the phase switch is in the 180° position the left channel is "out of
phase " when compared to the right.
The loudness compensation switch is also connected to the first section of the volume control.
Out of phase program source material is easily corrected with the use
of this switch.
3
POWER AMPLIFIER SECTION
There are 9 transistors in each power amplifier. The input stage is
a pair of matched transistors arranged as an emitter coupled amplifier
with two inputs and one output. The program from the preamplifier
connects to one of the inputs, the second input is fed from the feed-
back loop that is around the power amplifier section. Both AC and DC
feedback are used around the power amplifier section. Noise and distortion are reduced by the use of a large quantity of feedback.
The power transistors are mounted on oversized anodized heat sinks.
The heat sinks assure that under normal operation the transistors will
operate at a low temperature. If temperatures increase due to shorted
speaker, or restricted ventilation, an automatic temperature sensing
device turns off the MA5100. The device operates automatically at a
preset temperature. The MA 5100 will turn on again when the temperature has decreased to normal operation. This additional feature gives
your MA5100 complete reliability under the most extreme operating
conditions.
To further insure reliability a special power output SENTRY MONITOR-
ING CIRCUIT prevents failure of the power output transistors due to
abnormal mismatch of the output. When your MA5100 operates nor-
mally the SENTRY MONITORING CIRCUIT has no effect on signals
passing through the power amplifier. If the power dissipation should
rise above normal operation, the SENTRY MONITORING CIRCUIT re-
stricts the drive to the output transistors. The action of the SENTRY
MONITORING CIRCUIT is immediate for any input signal or load
combination. This arrangement assures complete circuit reliability.
Only Mclntosh gives you this degree of protection.
POWER SUPPLY SECTION
There are four separate power supply sections. One positive and one
negative high current supply is used for the output stages. One positive
and one negative low current supply is used for the preamplifier and
power amplifier input stages. All supplies are full wave and use silicon
rectifiers. Adequate filtering is used to assure an absolute minimum of
output hum. The power output stage filter capacitors have very high
capacity, which allows full power output below 20 Hz. The power transformer is generous in size and runs cool, even under heavy use.
MA
4
5100
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