What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

McIntosh MX 110

 The MX110 combines in one unit an extremely low-distortion preamplifier with a highly sensitive FM multiplex stereo tuner. Every desirable feature of a tuner and a preamplifier is included in this design. Interstation noise suppression, tuning indicator, FM multiplex indicator, individual channel bass controls, individual channel treble controls, electronic phase switch have all been engineered into the MX110. The INPUT SELECTOR gives you a choice of six different program sources. The MODE SELECTOR is a newly developed control which makes it very easy to balance a stereo system. It is designed to add left to right for monophonic operation, to control the left to right stereo perspective or to compare the left and right channels of a stereo program. The loudness of the phono channels and the auxiliary channel may be balanced to the tuner loudness.  These adjusting controls are located on the top of the MX110 behind the front panel. By releasing the PANLOC buttons on the front panel, you can slide the MX110 out of its mounting until the second latch engages. The top mounted LEVEL set controls are now available.
The Mclntosh designed PANLOC system is the first professional installation technique to be used on stereo instruments. The PANLOC system gives you absolute ease of installation, operation, and maintenance.
The Mclntosh MX110 is a beautifully engineered control center for the finest stereo sound systems. The extreme care in manufacturing, in layout design and in thermal engineering promises the usual Mclntosh extra values of reliability, performance, and long life.
 The MX110 combines in one convenient instrument an FM Tuner, a Multiplex Decoder ana a Stereo Preamplifier. You mount only this one unit, connect it to your power amplifier and speakerss and you're ready to go.
The electronic circuits in the preamplifier are so skillfully engineered that a wave-form analusis at 3 volts output shows typically only 1/20th of 1% distortion 20 cycles through 20,000 cycles. The stability of the tuner circuits has been improved to the point that A.F.C. is no longer needed. Sensitivity is also increased over previous models. The MX110 uses a newly developed indicator which lights whenever the tuner is centred on a station broadcasting the 19KC carrier for miltiplex stereo. The control circuit for the indicator respondes only to the 19KC and is insensitive to noise.
The MX110 also uses the new, exclusive McIntosh PANLOC method installation. The PANLOC system gives you absolute ease of installation, operation, and maintenance. PANLOC is the first professional installation technique to be used on stereo instruments.
The MX110 is a model of convenience, careful planning and rigorous manufacturing methods.
 The radio-frequency amplifier of the MX110 is a "cascode" type circuit. The circuit is specially designed to amplify weak signals with less noise and distortion. By carefully tuning this RF amplifier during manufacturing and controlling other circuit constants, spurious response rejection is improved. The high-frequency oscillator mechanical layout is engineered for minimum response to temperature variations. In fact the combination of mechanical and electronic design is so unusually good in this circuit that automatic frequency control is not needed in the MX110. The mixer output is amplified by four flat-topped intermediate frequency amplifiers. The transformers used in the LF. amplifiers are designed for maximum adjacent channel rejection, for electrical stability, and for electrical and mechanical resistance to shock and vibration.
The R.F. and I.F. circuits of the MX110 are completely shielded and exceed the FCC requirements for suppression of oscillator radiation. Either a 300 ohm or 75 ohm antenna may be used with the MX110. A VHF television antenna which is suitable for FM reception can be connected to the MX110. In the MX110, a new type of mechanical tuning assembly gives smooth flywheel tuning. By controlling the relations between mass and mechanical resistance, and dividing work loads in the dial drive system, it becomes nearly impossible to detect any backlash. Yet the entire dial drive is a model of mechanical stability. For smooth, quiet action and extended life with virtually no wear, a teflon lined dial pointer carriage and nylon pulleys are used in the dial cord assembly.
 The multiplex decoder uses a special Mclntosh developed detecting circuit. One of the advantages of this circuit is the elimination of the critical adjustments necessary with commonly used matrixing methods. This circuit detects the L+R sidebands and automatically matrixes the recovered information with the L+R main carrier signal. This circuit then yields the left and the right program with maximum separation. A temperature stabilized 19KC amplifier locks-in a highly stable push-pull synchronous oscillator. Apart from other advantages, this method provides greatest noise immunity. Balanced detectors cancel 19KC and 38KC components in the output and insure low distortion.
A three-section sharp cut off filter rejects SCA interference and reduces susceptibility to spurious signals.
The MX110 has an MPX stereo indicator that lights when the dial pointer crosses a station broadcasting MPX stereo. A unique circuit using a transistor operates the MPX stereo indicator. The transistor is controlled by a differential detecting circuit that amplifies the 19KC pilot signal. This circuit automatically discriminates between the 19KC signal and noise.
 The MX110 audio amplifier consists of three negative-feedback amplifying sections in duplicate for the left and right stereo channels and a separate L+R monophonic amplifier. The first section in each channel is a feedback preamplifier used to amplify and compensate for the input signals coming from phonograph pickups or tape heads. Level set controls are connected into the output circuit of this preamplifier section when the INPUT SELECTOR is switched to PHONO 1 or PHONO 2. These controls may be used to maintain uniform loudness between phono and tuner inputs. Skillful layout, grounding, and shielding for low-hum pickup, metal film resistors, low-noise tubes and extreme care in manufacturing combine to reduce noise and hum in the input amplifiers. The second amplifier section in each channel is a cathode follower. The sharp cut-off (18db per octave) rumble and high-frequency filters are associated with this section. Inputlevel set controls for the auxiliary inputs are associated with this section. All the level set controls are conveniently accessible The third amplifier section is a two stage negative feedback amplifier. The variable bass and treble controls are included in the feedback loop to maintain the lowest possible distortion. For example a wave meter analysis of the three amplifier sections of the MX110 shows less than 1/10 of 1% distortion at 3 volts output. The MODE SELECTOR, balance controls and left and right outputs are associated with the third amplifier section. The L+R monophonic amplifying section is a feedback summing amplifier. It supplies monophonic output as well as L+R output.
The power supply of the MX110 has received very special design attention. Three separate rectifier circuits are used. First, a full-wave rectifier supplies D.C. to the heaters of all audio stages. A second bridge rectifier supplies D.C. to the anodes of the audio stages. Then a third full-wave rectifier supplies D.C. to the tuner stages. This elaborate power supply design insures the lowest possible background hum level and also the maximum stability. In addition to this careful work the power transformer uses special magnetic shielding to minimize possible hum pickup in the MX110 as well as in any other equipment used with it.

Sensitivity:  Better than 2.5 microvolts at 100% modulation.
R.F. Amplifier:  Cascode.
LF. Amplifiers:  Four.
Limiters:  Two.
LF. Bandwidth:  200KC flat top.
LF. Transformers:  Mechanically captive.
Muting:  LF. injected.
Tuning Indicator:  Tuning is indicated by an electron ray tube.
Frequency Response:  Within ± 1db 20 to 20,000 cycles. (Including 75 microseconds deemphasis.)
Hum:  Greater than 70db or more below 100% mod. (Audio tubes have D.C. on the filaments.)
Drift:  Less than 25 KC.
Ant. Input Impedance:  300 balanced, 75 ohms unbalanced.
Radiation:  Substantially below F.C.C. requirements.
Distortion:  Less than 0.6% distortion at 100% modulation, ± 75KC deviation above 2.5 microvolts at antenna.
MPX Decoder
Hum Level :  Better than 60db below 100% stereo modulation.
Distortion :  Less than 0.3% (Multiplex Decoder only).
Channel Separation :  Better than 30db at 1000 cps.
Suppression of Pilot (19KC), and Carrier (38KC) :  Greater than 40db below 100% modulation.
Front Panel Stereo Indicator Light :   Activated by 19KC pilot carrier only.
Inputs (Total 5 each channel):
Main Stereo Outputs, 1 Tape Stereo Output, 1 L+R Output.
AC AUX Outlets:  1 unswitched, 2 switched.
Input Selector: Total 6 positions: AUX, MPX, FM, PHONO 1, PHONO 2, TAPE HEADS.
Mode Selector: Total 7 positions: L TO L&R, R TO L&R, STEREO REV., STEREO, MONO, L+R TO L, L+R TO R.
Tone: Dual treble and bass negative-feedback controls with slip clutch for independent
adjustment of each channel.
Bass Boost :  15db at 50 cycles.
Bass Cut :  18db at 50 cycles.
Treble Boost :  15db at 10,000 cycles.
Treble Cut :  15db at 10,000 cycles.
Balance: Turn to right to emphasize the right channel. Turn to the left to emphasize the left channel.
Phase: 2 positions: NORMAL or REVERSED:
Changing phase does not increase distor- tion. H.F. Cutoff Filter: 2 positions: Flat, or 5KC cutoff. (20db per octave.) L.F. Cutoff Filter: 2 positions: Flat, or 50 cycles cutoff. (20db per octave.)
Loudness: Fletcher Munson compensation.
Tape Monitor: 2 positions: IN and OUT. For comparison of recorded tape with program source after recording.
Tuning: Flywheel tuning—no backlash.
Muting: 2 positions: IN or OUT for interstation noise suppression.
Level Set: Three left and three right controls. 2 for AUX, 2 for PHONO 1, and 2 for PHONO 2. These controls are located back of the front panel on the top of the MX110.
AC Power—Concentric with BALANCE control: ON-OFF.
Frequency Response:  ±½db 20 to 20,000 cycles.
Distortion:  Less than 0.2% at rated output.
Hum and Noise:
High-level inputs :  80db below rated output.
Low-level inputs :  less than 3 microvolts at input terminals.
Input Sensitivity:
AUX :  0.3 volt at 200K.
PHONO 1 :  3 millivolts at 47K.
PHONO 2 :  3 millivolts at 47K.
TAPE HEAD :  3 millivolts at 220K.
TAPE MONITOR :  0.3 volt at 100K.
MAIN :  3 volts 2 in parallel each channel.
L+R :  3 volts.
TAPE :  From FM at 100% modulation 0.9 volt from PHONO when cartridge output is 9.0 millivolts—0.9 volt; with rated input —0.3 volt.
POWER REQUIREMENTS: 105-125 volts AC 50/60 cycles; 75 watts.
FUSE: 1 amp. Slo-Blo.
1 6DS4 R.F. -1 amplifier (nuvistor)
1 12AT7 R.F.-2 mixer
1 6AB4 Oscillator
1 6AU6 IF-1
1 6AU6 IF-2
1 6AU6 lF-3/Limiter 1
1 6CS6 IF-4/Limiter2
1 12AT7 Muting/L+R Amplifier
1 6HU6/EM87 Tuning Indicator
1 6D10 FM AUDIO/Left and Right
1st Audio Amplifier
1 6U8 MPX Amplifier and 19KC
Separator/Indicator control
1 12AU7 MPX 38KC Oscillator
1 12AX7 Phono Preamplifier Left
1 12AX7 Phono Preamplifier Right
1 12AX7 Left and Right 2nd Audio Amplifier
1 6U8 Left 3rd Audio Amplifier
1 6U8 Right 3rd Audio Amplifier
2 DiodesDiscriminator
1 DiodeMuting and Tuning Eye Detectors
1 Diode AGC Clamp
4 Diodes Balanced MPX Detectors
2 Diodes Balanced Det. for Indicator Light
2 Silicon Diodes DC Filament Supply
1 MA113 Transistor-Indicator Light Switch
4 Selenium Rectifiers High and Low Voltage Supply
Chassis:  16 inches wide; 57/16 inches high; 13 inches deep including connectors.
Front Panel:  16 inches wide; 57/16 inches high.
Knob Clearance:  1½ inches.
Chassis: 27½ pounds.
Shipping Weight:  36 pounds.
Finish:  Anodized gold and black (front panel).
Installation Convenient, professional PANLOC.

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