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

Hitachi SR-802

 "Our SR 802 tuner amplifier will set you back over £200.
You could pay more, and you could pay a lt less .
But cheap alternatives have a nasty habit of giving up when  he going gets hot."

We guarantee this won't happen with a SR 802. It's got a built-in protection circuit tolook after your power transistors and speakers.
At the first sign of trouble it'll turn itself off.
And there's warning light on the front panel to keep you in the picture.
The tuner on the SR802 has some useful refinements too. Like the FM 'muting' circuit which eliminates all inter-station noise is being selected.  And there's one more feature on the SR 802 you won't find on every turner amp.
It's called reliability. And it's standard on all Hitachi equipment.
So is the Hitachi 2-year guarantee.

Tuner Sections

FM Stereo Frequency Range:  88 -108 MHz
Usable Sensitivity (IHF):  1,7 µV
Harmonic Distortion Factor:
Mono : 0,15% (400 Hz)
Stereo : 0,25% (400 Hz)
Signal-to-Noise Ratio:  74 dB
Selectivity (IHF):  80 dB
Image Rejection Ratio:  85 dB
IF Rejection Ratio:  100 dB
Capture Ratio: 1 dB
AM Suppression Ratio:  55 dB
FM Stereo Separation:  45 dB (1kHz)

AM Frequency Range:  530 - 1605 kHz
Usable Sensitivity:  300 µV/m (S/N 20 dB, 20 µV (IHF)
Image Rejection Ratio:  50 dB
IF rejection Ratio:  50 dB
Signal-to-Noise Ratio:  50 dB
Selectivity (IHF):  35 dB

Audio Section
Music Power (IHF):
80 W/ch + 80 W/ch (8 Ω, 1 kHz, 0,5% THD)
70 W/ch + 70 W/ch (4 Ω, 1 kHz, 0,5% THD)
RMS Power Output (both channel driven):  50 watts per channel, min. RMS, at 8 Ω from 20 - 20,000 Hz, with no mor than 0,5% THD
60 W/ch + 60 W/ch (8 Ω, 1 kHz, 0,5% THD)
70 W/ch + 70 W/ch (4 Ω, 1 kHz, 0,5% THD)
Frequency Characteristics:  10 Hz - 30 kHz (±1 dB)
Harmonic Distortion: 
At rated output : 0,5%
At ½ rated output : 0,05%
Power bandwidth:  10 - 40,000 Hz

Tone Control:
Bass : ±10 dB at 100 Hz
Treble : ±10 dB at 10 kHz
Power Source:  100V/120V/220V/240V  50/60 Hz
Dimensions (W x H x D): 

Toshiba SA-514

 Hi-Fi Stereo / Quadro Receiver SA-514
A new highlight in the traditional line of Toshiba Hi-Fi receivers. Quadro unlimited and Stereo at its best.

Quadro Decoder - for RM,  SQ  and  Discrete  modes  and  de-modulation of  CD-4

FM Muting - for suppression of interstation noise

Two Tape Monitor Push-Buttons - permit the connection of two tape recorders for dubbing from tape onto tape
 Loudness Contour Circuits - and two Auxiliary inputs for the connection of additional sound sources; Hi and Low filters for suppression of noise on older records and tapes

Four level-set Controls - for separate control of each channel plus master volume control

OCL Circuits - in the power amplifiers eliminate capacitors for optimum transient response.

FETs and Ceramic Filters -  in the tuner and IF sections ensure low-noise reception combined with excellent sensitivity.

BTL Circuits - provide Stereo reproduction with two speakers using the full power of four channels.

Multiple Speaker Switch -  for complex switching of up to 8 speakers in two groups.
Tuner Sections

FM Stereo Frequency Range:  88 -108 MHz
Usable Sensitivity (IHF):  2µV
Distortion Factor:
Mono : 0,4% (400 Hz, 100%)
Stereo : 0,8% (400 Hz, 100%)
Signal-to-Noise Ratio:  66 dB
Frequency Response:  20 Hz - 15 kHz (+1 -2 dB)
Selectivity (IHF):  60 dB
Image Rejection Ratio:  40 dB
IF Rejection Ratio:  70 dB
Capture Ratio: 2 dB
Spurious Rejection Ratio:  100 dB
Am Soppression Ratio:  40 dB
FM Stereo Separation:  40 dB (1kHz)
AM Frequency Range:  530 - 1605 kHz
Usable Sensitivity:  300 µV/m (S/N 20 dB, 15 µV (IHF)
Distortion Factor:  1%
Image Rejection Ratio:  40 dB
IF rejection Ratio:  30 dB
Signal-to-Noise Ratio:  40 dB
Selectivity:  25 dB (±10 kHz)
Audio Section
Continous Power (20 - 20,000 Hz, 4-channel driven):
15 W per channel into 8 Ω
18 W per channel into 4 Ω
Output (4 CH)at 1 kHz, 4-channel driven:
18 W per channel into 8 Ω
24 W per channel into 4 Ω
Output (4 CH) at each channel driven:
25 W per channel into 8 Ω
35 W per channel into 4 Ω
Continous Power (20 - 20,000 Hz,  2-channel driven):
40 W per channel into 8 Ω
Output BTL (2 CH) at 1 kHz, 2 -channel driven:
45 W per channel into 8 Ω
Output BTL (2 CH) at each channel driven:
60 W per channel into 8 Ω
Music Power:
120 W at 8 Ω
150 W at 4 Ω
190 W at 8 Ω BTL
Harmonic Distortion:  less than 0,4%
Power bandwidth:  20 - 25,000 Hz (IHF, 4-channel driven)
Input Sensitivity/Impedance:
Phono 1 (CC):  30 mV/70 k Ω
Phono 2 (MM):  25 mV/100k Ω
Aux (2 CH):  150 mV/50 k Ω
Tape Monitor 1, 2 (4 CH):  150 mV/50 k Ω
Recording Output level:  Tape Rec 150 mV,  DIN 30 mV
Signal-to-Noise Ratio: 
Phono 1 (CC):  70 dB (30 mV)
Phono 2 (MM):  65 dB (25 mV)
Aux (2CH):  75 dB (150 mV)
Residual Noise:  1,5 mV
Tone Control:
Bass : ±10 dB at 100 Hz
Treble : ±10 dB at 10 kHz
Loudness Control:  ±10 dB (100 Hz at vol. 20%)
Damping Factor:  40 dB
Semiconductors:  69 Transistors; 1 FETs; 45 Diodes; 12 IC
Power Source:  100V/120V/220V/240V  50/60 Hz
Dimensions (W x H x D):  500 x 127 x 380 mm ( 19 ½" x 5" x 15")
Weight:  12 kg

Marantz CD 75II

 The CD 75II (1989) Compact Disc Player is a much improved version of the popular award winning Marantz CD 65/75 model. This player offers a sound quality that has set a standard against which other players are judged. To this is added full remote control and the convenience of Favourite Track Selection, High performance low distortion digital-to-analogue convertor chips are used with four times oversampling and Marantz digital filtering. Independent power supplies ensure that no digital noise reaches the analogue output stages. Treble delicacy or detail is retained that can often be lost when the servos that ensure accurate tracking of the disc operate. The power supplies guarantee tight bass control. Direct access is given to 99-tracks with a 20-step memory which can be programmed by track, index point or time. The CD75II has both fixed and variable level outputs (phono).
 Special Features
Twin 16-bit DAC with four times oversampling and digital filtering
Three separate power supplies for mechanical, digital and analogue audio stages.
Fully floating die-cast laser mechanism (CDM 1 MkII)
Favourite Track Selection
Full remote control
Optical and electronic digital output
Headphone output with independent level control

Marantz CD 75 II
Frequency Range:  2 Hz - 20 kHz
Dynamic Range:  less than 96 dB
Signal-to-Noise Ratio:  less than 102 dB
Channel Separation:   less than 100 dB
Total Harmonic Distortion:  0,0015%
IM Distortion:  less than  -90 dB
Phase Linearity:  ± 0.2%
Wow and Flutter:  Quartz precision
D/A Converter:  2 x 16 bit
Audio Output level:  2 V/RMS
Headphone Output:  yes, variable level
Digital Output (0.5 V into 75 Ω load):  1 phono + optical
Four-times Oversampling:  yes
Power Supply:  220 - 240 V AC
Dimensions (W x H x D):  420 x 90 x 300 mm
Weight Net :  4 kg

Marantz CD 65II

 The CD 65II (1989) Compact Disc Player is a much improved version of the popular award winning Marantz CD 65/75 model. The best value is offered by the CD 65II which shares the same criticallywell-received sound quality of the CD 75II. Whereas the CD 75II has both optical and electronic digital outputs teh CD 65II has only an electronic output. Both players are offered with remote control but this provides only basic play and search functions on the CD 65II. The CD 75II additionally offers remote programming and volume control
 Special Features
Twin 16-bit DAC with four times oversampling and digital filtering
Three separate power supplies for mechanical, digital and analogue audio stages.
Fully floating die-cast laser mechanism (CDM 1 MkII)
Remote control
Electronic digital output

Marantz CD 65 II
Frequency Range:  2 Hz - 20 kHz
Dynamic Range:  less than 96 dB
Signal-to-Noise Ratio:  less than 102 dB
Channel Separation:   less than 100 dB
Total Harmonic Distortion:  0,0015%
IM Distortion:  less than  -90 dB
Phase Linearity:  ± 0.2%
Wow and Flutter:  Quartz precision
D/A Converter:  2 x 16 bit
Audio Output level:  2 V/RMS
Headphone Output:  yes
Digital Output (0.5 V into 75 Ω load):  1 phono
Four-times Oversampling:  yes
Power Supply:  220 - 240 V AC
Dimensions (W x H x D):  420 x 90 x 300 mm
Weight Net :  4 kg

Akai AS-1080 DB

 4-Channel Stereo Receiver
4-channel Dolby recording and payback  with an ordinary tape deck for first time in audio history. This is only one of the many outstanding features of the new AS-1080 DB. This new 4/2 channel compatible receiver incorporates all the latest engineering techniques and offers performance quality to match anything on the market todey. Yet the cost of this deluxe model is far below what you would expect to pay for such quality. Robust 3mm thick aluminium front panel. Easy-to-operate precise controls. Designed for efficient operation of present and future audio capability.
 All-Stage Direct Coupled OCL Pure Complementary Power Amplifier
40 watts per channel continous power output (80 watts per channel at 2-Ch power Doubler), minimum RMS at 8 ohms load impedance with no more than 0,2% distortion. These outstanding specifications are the result of employing an all-stage direct-coupled OCL pure complementary 4 Power IC circuit in the all important power section.

Power Transistor Protection Circuit
A protection circuit is activated in case of a short caused by a wrong speaker connection or when input is excessive to protect the power transistors. Further, this circuit cancels the irritating speaker shock noise when the power switch is turned On or Off

Varied 4-channel operation includes Dolby 4-channel performance (a first in the field of audio)
This 4-channel / 2-channel compatible unit, in addition to regular and discrete stereo, SQ Full Logic and Matrix 4-channel stereo, and CD-4 capability, also features 4-channel Dolby recording and playback with an ordinary 4-CH tape deck.

SQ Full Logic Decoder Circuit
The SQ Full Logic decoder of this model is a superior Front/Back Logic wave matching circuit employing a 6-pole phase shifter for excellent front and rear channel separation.  3 advanced large scale Sony ICs.  SQ Indicator lamp.

Matrix Decoder Circuit
Facilitates playback of matrix encoded phonograph records.
 CD-4 Demodulator Circuit and Separation Adjust
A built-in CD-4 demodulator circuit and CD-4 Separation Adjusters facilitate easy playback of CD-4 records. Front panel CD-4 indicator Lamp. CD-4 test record included in standard accessories.

Four separate Dolby Circuits
A separate Dolby Circuit for each channel enables 4-channel Dolby Recording and Playback with an ordinary 4-channel tape recorder or tape deck for the first time in audio history.

Dolby Operation
The Dolby System of this model facilitates recording and playback with an ordinary 4-channel tape recorder or tape deck. Precise Dolby Controls, a Dolby Level Meter Switch, and Dolby Level Adjustment Tape (included in the standard accessories) enable easy and precise Dolby System level adjustment, 40channel or 2-channel Dolby recording and playback, 4-channel or 2-channel Dolby Dubbing (Dolby recording from ordinary tape playback)from Tape 1 to Tape 2 System, and Dolby FM broadcast reception are among the outstanding Dolby capabilities of this model.

Two compelete 4-channel Tape Deck Connections for varied recording and Dubbing techniques.
Multiple Source Selector, Tape Monitor, and Mode Switch positions and two complete tape systems for a plethora of 2-channel or 4-channel recording and dubbing techniques. Use Tape 1 and tape 2 systems separately or simultaneously. Easy dubbing to and from Tape1 and tape 2 Systems. Also equipped with two complete 4-channel speaker connections.

Two Channel Power Doubler
Setting the Speaker Switch to 2-Ch Power Doubler switches the amplifiers to BTL for all available power in 2-channel mode. Further, transition is smoothe with no irritating speaker noise.

Up-to-Date High Efficiency IC Circuitry in FM IF Section
This totally new up-to-date element is comprised of a 6-stage limiter circuit, a detection circuit, and several auxiliary circuits and does the work of 213 separate parts using parts available to date. Namely, it would require 100 transistors, 84 resistors, 25 dides and 4 condensers to accomplish the same thing. Further, because the detection circuit employs "Quadrature" detection, excellent linearity and low distortion is attained over an exceptionally wide frequency range.

PLL  MPX Section for Good Separation and Low Distortion
This model features the new PLL (Phase Lock Loop) circuit which locks the 19 kHz FM pilot signal phase to the phase of the 38 kHz switching signal for complete stability. Separation better than 40 dB. Less than 0,4% THD.

Automatic FM Center Tuning and FM Mute Switch
Perfect center tuning is always attained. With AFC (Automatic Frequency Control), it is not necessary to tune to exact FM center frequency. Simply bring the needle within the FM center scale of the meter and perfect center tuning is automatically of fluctuation in power supply voltage or temperature. An FM Mute Switch enables the operator to effectively cut noise originating prior to antenna input.

Large Balanced Flywheel Tuning
Large balanced flywheel tuning and superior FM and Am circuitry provides smooth and easy "power steering" tuning and top FM and Am reception.

Loudness Circuit for Balanced Sound at Low Volume
Boosts bass and treble response for balanced sound at low volume

High and Low Filter Switches
Eliminates high and low frequency disturbances for clearer playback

4-Channel Remote Control Balance
A rear panel Remote Control Jack accomodates AKAI optional accessory Remote Control Unit RC-4CH for remote control of front/rear and left/right speaker balance and volume

FM 4-CH Output Terminal
Equipped with rear panel FM 4-channel output terminal for connection of an adapter for future FM 4-CH broadcast reception.

 Other Features
Two full speaker systems feature easy push button connectionn.
300 Ω and 75 Ω antenna terminals with distance/local switch plus AM bar antenna.
Separate front and rear channel Bass and Treble controls for perfect tone control.
Front and rear channel headphone jacks.

Amplifier Section
Continuous Power Output 4-channels driven:
40 watts per channel, min. RMS, at 8 Ω from 20 to 20,000 Hz, with no more than 0,2% THD
4 x 50 watts into 8 Ω at 1 kHz with no more than 0,2% THD
Continuous Power Output 2-channel driven (Power Doubler ON):
80 watts per channel,min.RMS at 8 Ω from 20 to 20,000 Hz, with no more than 0,2% THD
2 x 100 watts into 8 Ω at 1 kHz with no more than 0,2% THD
Power Bandwidth (IHF):  10 Hz to 60,000 Hz / 8 Ω (distortion within 0,2%)
Input Sensitivity:
Phono : 3 mV/ 47 k Ω (CD-4 1,5 mV/ 47 k Ω)
AUX : 160 mV/47 k Ω
Tape 1 & 2 : 160 mV/47 k Ω
Signal-to-Noise Ratio (IHF): 
Phono : Better than 80 dB
AUX : Better than 90 dB
Channel Separation (IHF):
Phono :  Better than 50 dB (at 1kHz)
Equalizer: RIAA Standard ± 1 dB (Phono)
Tone Control
Bass : ±10 dB at 100 Hz
Treble : ±10 dB at 10 kHz
Loudness Control:  +9 dB at 100 Hz,  +4 dB at 10 kHz (Volume Control at -30 dB position)
High : -6 dB at 10 kHz
Low : -10 dB at 50 Hz
Dolby System:  Dolby "B" processor
Dolby Tone:  400 Hz / Rec. Out, PIN 150 mV
FM Tuner Section
Frequency Range:  88 MHz to 108 MHz
Sensitivity (IHF):  1,9 µV
Capture Ratio (IHF):  1.0 dB
Selectivity (IHF):  Better than 70 dB at 98 MHz
Signal-to-Noise Ratio:  Better than 70 dB
Image Rejection:  better than 75 dB at 98 MHz
IF Rejection:  Better than 90 dB at 98 MHz
Spurious Rejection:  better tham 80 dB at 98 MHz
Harmonic Distortion
Monaural : less than 0,2%
Stereo : less than 0,4%
FM Stereo Separation:  Better than 40 dB (1kHz)
FM Muting:  Variable (3 to 300 µV) ON - OFF
Antenna Input Impedance: 
Balanced : 300 Ω
Unbalanced : 75 Ω
AM Tuner Section
Frequency Range:  535 kHz to 1,605 kHz
Sensitivity (IHF): 
200 µV/m (Bar antenna)
5 µV (External antenna)
Image Rejection:  Better than 55 dB at 1,000 kHz
IF Rejection:  Better than 45 dB at 1,000 kHz
Selectivity (IHF):  better than 30 dB at 1,000 kHz
AM Distortion:  Less than 0,6%
Signal-to-Noise ratio:  Better than 50 dB
General Section
Semiconductors:  1 FET, 90 Transistors, 68 Diodes, 18 ICs
Power Requirement:  110 - 120 V, 220 - 240 V (Switchable) 50/60 Hz
Dimensions (W x H x D):  520 x 182 x 409 mm  (20,5" x 7,2" x 16,1")
Weight:  19,3 kg (42,5 lbs)

McIntosh MR 80

 Engineering direction dictated a tuner design governed by insistence on great flexibility and ease of use. This had to be done while designing an RF section with great sensitivity and the world's best selectivity in keeping with the needs of low distortion.
These values were achieved and they retain the Mclntosh reputation of outstanding performance, long life and reliability.
Tuning in a station on the MR 80 is achieved electronically.
This assures long term trouble free operation.
You can tune a station on the MR 80 four different ways.
1. Manual tuning by rotating the main tuning knob.
2. Auto Scan automatically searches for the next available station up or down in frequency.
3. Presets - allows you to select your four most listened to stations that can be tuned at the touch of your finger tip.
4. Remote Scanning will allow the MR 80 to be tuned to a station from a remote location.
Two separate antenna systems can be connected to the MR 80.
1) An outdoor or indoor FM antenna, or 2) a cable input from your local cable company. The antenna selection is controlled by an electronic switching device containing more than 75 dB of isolation and no signal loss as might normally be found in external mechanical switch.
 Indicator Lights
Three indicator lights are provided. The uppermost STEREO indicates when a stereo broadcast is being received. The second, LOCK, indicates when the tuner is locked to the station. The third indicator light, FILTER, indicates when the stereo noise filter is in operation.

These touch pads select one of the four preset stations. Just touch to operate. A small rectangle will light above the pad indicating which preset has been selected.

Frequency Display Digital
The Frequency Display indicates the received frequency to the nearest 100 kHz.

Signal Column
A column of LED lamps respond to the signal strength of the station being received. The stronger the signal the higher the column reaches.

Auto Scan
AUTO SCAN is provided by two touch pads. These two touch pads start the tuner searching for a new station. It will scan until it stops at a station or reaches the end of the band. At the band end the tuner will reverse its scan direction.

Manual Tuning
When the MR 80 is turned on the circuitry automatically selects the manual or knob tuning control mode.

Selectivity Switch
Two degrees of IF selectivity are selectable by the SELECTIVITY switch. The NARROW or normal position provides adequate selectivity for stereo reception even under severe receiving conditions. Setting the SELECTIVITY switch to SUPER NARROW adds an additional 4-pole 4-zero quartz crystal filter. Use the SUPER NARROW position to receive stations from distant cities which are on channels adjacent to local stations.

Filter Switch
The MR 80 FILTER switch provides automatic stereo noise reduction on weak stereo stations.

Mode Switch
A two position MODE switch is provided so that you may select either automatic stereo or mono reception.

Headphone Jack
A HEADPHONE jack is provided to drive low impedance dynamic headphones from an internal power amplifier.

Scan Control
The SCAN control adjusts the speed at which the tuner searches for the next station.

Muting Control
MUTING suppresses the background noise and hiss normally heard between stations.

Volume Control
The VOLUME control has been precision tracked throughout the listening range (0 to - 65 dB) for accurate stereo balance.
 The MR 80 uses electronic varactor tuning instead of the more conventional mechanically gauged variable tuning capacitors. Variable tuning capacitors can with age collect dust and dirt, reducing their performance. Mclntosh uses double varactor diodes to provide the necessary tracking between the different tuned RF stages. When a weak distant station is adjacent to a strong local station the Preselector circuit will switch in an additional tuned circuit providing an extra degree of selectivity reducing the interference from the adjacent strong station.
After the RF amplifier two paralled tuned circuits are used to provide the proper load impedance for the bipolar transistor. These two tuned circuits greatly improve the image rejection and overload performance of the tuner, as well as increasing the RF selectivity.
An innovative new lock circuit was developed for use in the MR 80. This new circuit allows correct tuning without the use of a center tune meter. The MR 80 will be correctly tuned even if the station of the cable company is not on its correct frequency. This is done by the use of two operational amplifiers. The lock circuit will track a station even if it drifts 1 MHZ.

The mixer is a balanced matched dual J-FET and bipolar transistor circuit. A low loss toroidal phase splitting transformer is used as an impedance matching network in the gate circuit of the mixer eliminating even order spurious responses. The MR 80 has the narrowest IF bandwidth ever used in a stereo tuner. It is the correct width to let just one FM station through. The excellent selectivity of the MR 80 (210 kHz wide at 60 dB down) permits tuning to stations that are impossible to receive on ordinary tuners.
 After the mixer the signal is electronically switched to go either directly to the IF amplifier or to go through a quartz crystal filter. The SUPER NARROW selectivity position adds a 4 pole - 4 zero crystal filter to the other 5 IF filters. SUPER NARROW permits receiving stations never heard before with most other FM tuners. The 5 stages of IF amplification provide the necessary gain to reduce noise in the signal and interference from other stations. The 5 IF stages use piezoelectric fixed frequency filters in place of normal tuned circuits so the IF stages will always stay in alignment, even with age. The signal strength indicator column is summed off of all 5 IF stages instead of just 1 so it is looking at the signal strength throughout the entire IF system.

Following the selectivity section of the IF amplifier is the LIMITER. A total gain of 80 dB is used in this circuit. The use of very high gain in the limiter circuit produces hard limiting with very good impulse noise rejection. Limiter bandwidth is greater than 50 MHz, producing excellent detector capture characteristics. A broadband Foster-Seeley discriminator is used as the detector. This detector coupled with the broadband limiter produces unmeasurable noise and distortion.

The heart of the multiplex section is a new third generation phase locked loop (PLL) stereo decoder integrated circuit (IC). This PLL IC incorporates two special systems, an automatic variable separation control circuit to reduce background noise when receiving weak stereo stations, and tri-level digital waveform generation which eliminates interference from SCA signals and from the sidebands of adjacent channel FM signals.

The variable separation control is operated from the IF amplifier's signal strength detector. A smooth transition is provided from mono to stereo or from stereo to mono at weak signal levels to provide the optimum signal to noise ratio and best stereo separation for the prevailing signal conditions. The circuit operates only during stereo reception. It switches automatically to monophonic if the 19 kHz pilot tone is absent.

In the PLL the internal oscillator operates at 228kHz, locked onto the 19kHz pilot tone. The 228kHz, feeds a 3 stage Johnson counter via a binary divider to generate a series of square waves. Suitably connected NAND gates and exclusive OR gates produce the tri-level drive waveform for the various demodulators in the circuit. The usual square waveforms have been replaced in the PLL and decoder sections by tri-level waveforms. These tri-level forms contain no harmonics which are multiples of 2 or 3. This eliminates frequency translation and detection of interference from the side-bands of adjacent stations since the third harmonic of the sub-carrier (114kHz) is excluded. It also eliminates interference from SCA broadcasts since the third harmonic of the pilot tone (57kHz) is excluded.
Unwanted spurious audible components and phase jitter in the PLL are Inherently eliminated by this technique.
 Additional advantages of the phase locked loop stereo demodulation are the elimination of inductors to minimize drift, integral lamp driving capability to indicate the presence of the 19kHz pilot carrier, excellent channel separation over the entire audio frequency range, extremely low distortion, low output impedance, and transient-free mono/stereo switching.

Following the MPX decoder is the three position de-emphasis switch. The three different positions allow the MR 80 to be used in North America with standard 75ms de-emphasis and in Western Europe and the Far East with 50ms de-emphasis. The 25ms position is for use with an external noise reduction adapter.

An electronic blend filter circuit, implemented with two J-FETs of a quad J-FET package, is used to reduce out of phase noise when in the stereo mode and tuned to a weak station. This filter is actually a twin-T bandpass that blends the high and low frequencies, leaving separation unaffected at midfrequencies. This results in a greatly improved stereo image when the filter is required.

Special design attention has been given to the power supply section. Nine separate power circuits are used. Six of these are regulated to prevent loss of performance during a brown out. The - 15, - 5.2, 5, 15 and 30v use integrated circuit 3 terminal regulators, while the 3ma current source is made with discrete transistors because of the high voltage on the input terminal. The remaining voltages are used for the headphone amplifier and the touch control reference signal driver.

Mclntosh, recognizing the need for improved reliability, has designed a new circuit to drive incandecent lamps. This new circuit prevents the filaments from failing due to notching when operated on direct current. This failure mode can reduce lamp life from one half to one tenth of the data sheet value. In the MR 80 the three lamps that are used for STEREO, LOCK and FILTER indicators are operated on AC at lower than rated voltage to extend the useful life to well in excess of 15 years. Only Mclntosh brings you this feature.

TUNING:   88 to 108 MHz
ANTENNA INPUTS:  One 300 Ω  balanced and two 75 Ω unbalanced.
9.3 dBf (1.6mV) for 35 dB of quieting
14.7 dBf (3mV) for 50 dB of quieting
13.2 dBf (2.5mV) for 3% total noise and harmonic distortion
SIGNAL TO NOISE RATIO:  75 dB below 100% modulation
HARMONIC DISTORTION:  0.2% 20 Hz to 15 kHz, mono or stereo
Typically, 0.08% at 1000 Hz
INTERMODULATION DISTORTION:  0.15% mono or stereo for any combination of frequencies from 20 Hz to 15,000 Hz with peak modulation equal to 100% or less. Typically 0.1%
FREQUENCY RESPONSE:  Mono and Stereo ± 1 dB 20 Hz to 15 kHz with 75, 50 or 25ms de-emphasis
Adjacent channel : 8 dB (Narrow); 60 dB (Super Narrow)
Alternate channel : 90 dB  (Narrow); 110 dB (Super Narrow)
TUNER IM (RF):  -23 dBm for 2 signals 1 MHz apart
MAXIMUM SIGNAL INPUT:  8 volts across 75W (1W) antenna terminal will not increase harmonic or intermodulation distortion.
AUDIO HUM:  75 dB down from 100% modulation
MUTING:  70 dB noise reduction between stations
SCA REJECTION:  60 dB minimum
STEREO SEPARATION:  50 dB to 1000 Hz
STEREO FILTER:  10 dB noise reduction
VARIABLE :  2.5V into 47k Ω
FIXED :  1V into 47k Ω
POWER REQUIREMENTS:  120 volts,  50/60 Hz.
POWER Consumptions:  25 watts
57 Transistors, 68 Integrated Circuits, 81 Diodes, 4 LED Displays, 18 LED's, 7 Neon Lamps
Front panel measures:  406 mm (16") wide  by 138 mm (5-7/16") high.
Chassis measures: 375 mm (14-3/4") wide by 122 mm (4-13/16") high by 330mm (13") deep , including connectors.
Knob clearance required is 32 mm (1-1/4") in front of mounting panel.
FINISH:  Front panel is anodized gold and black with special gold/teal nomenclature illumination. Chassis is black.
MOUNTING:  Mclntosh developed professional PANLOC
WEIGHT:  12,2 kg (27 pounds) net,  17,7 kg (39 pounds) in shipping carton

Accuphase P-250

 High power output of 100 wats per channel into 8 ohms with clean sound quality at all listening levels. This high power capability, with distortion at less than 0,1% from 20 to 20,000 Hz is fully guaranteed. Heavy duty power transistors in a parallel push-pull drive output stage and large heat sinks back up this Accuphase warranty.
High power amplifiers need an especially reliable power supply that must not only provide the energy to drive the speakers but the capacity to store and deliver adeguate power to trace the sharpest fluctuating signal. The P-250 has just such a power supply with an oversize power transformaer and two giant 20,000µF filter capacitors that can easily supply the energy required to deliver 280 watts of continuous power into 4 ohms. A severe rise in distortion when  volume is reduced to low levels is a problem with many high power amplifiers, but not so with the P-250 in which such distortion has been eliminated to the lowest possible limit. It permits enjoyment of clean, clear pianissimo passages at All volume levels.
 Speaker Damping Control enhances characteristic tonal qualities speakers.
The damping factor of solid state amplifiers is generally very large and ideal for damping the speakers. However, some speakers require en amplifier with a low damping factor to reproduce rich, full-bodied sound. The P-250 has a Speaker Damping Control which permits choice of three damping factors and induces maximum potential performance from any speaker. Damping factor with an 8 ohm  load becomes more than 50 when this control is set to Normal. Likewise, it is 5 at Medium position, and 1 at at Soft position. It enables choosing the speaker sound that one prefers.

Foolproof protection Circuit safeguards power transistors and speakers.
The P-250 has a built-in Protection Circuit which guards against damage to speakers or power transistors in case of shorts when the speakers are connected, or when abnormally low impedance output load connections are made. If the speakers are shorted, this circuit automatically cuts them from the amplifier.
 Large size power meters.
Large size power meters indicate power output in decibels (dB). The meters also provide indications to read output power level directly in watts. Switch selection of three ranges, 0 dB; -10 dB and -20 dB, permit both low and high power measurement. At 0 dB reading indicates power output of 100 watts into 8 ohms when the meter range switch is set to 0 dB.
 Plenty of Input / output terminals.
Plenty of outputs are available to which three pairs of stereo speakers can be connected, and switch selected. Accommodations for two pairs of input systems are also provided, and they too can be switch selscted. One pair of input system is provided on the front sub-panel for easy accessibility.

Power Output (both channel driven from 20 Hz to 20,000 Hz with no more than 0,1% THD):
140 watts per channel, min. RMS, at 4 Ω
100 watts per channel, min. RMS, at 8 Ω
50 watts per channel, min. RMS, at 16 Ω
Total Harmonic Distortion (from 20 Hz to 20,000 Hz at any power output from ¼ watt to rated power):
4 Ω : 0,1% max.
8 Ω : 0,1% max.
16 Ω : 0,1% max.
Imtermodulation Distortion:  will not exceed 0,1% at rated power output for any combination of frequencies between 20 Hz and 20,000 Hz
Frequency Response:
20 Hz to 20,000 Hz : +0; -0,2 dB at rated power output
5 Hz to 90,000 Hz : +0; -3 dB at rated power output
Slewing Rate:  more than 15 V/µS
Damping Factor (at 8 Ω load, 20 Hz to 20,000 Hz ):
With "Speakr Damping" switch set to:
"Normal" : 50
"Medium" : 5
"Soft" : 1
Input Sensitivity/ Impedance:
1,0 Volt, 100 k Ω, for rated output at the max. Level control
Hum and Noise:  94 dB below rated output
Power Level Meter
Meter is calibrated to read 0 dB when amplifier produces 100 watts into 8 Ω load.
Meter Range switch is provided to increase meter sensitivity by 10 dB or 20 dB
Output Load Impedance:  4, 8 and 16 Ω
Audio Bandpass Filter:
Cut off Frequency;
LOW : 17 Hz 18 dB/oct
HIGH : 24 kHz 18 dB/oct
Headphone Jack:  For listening with low impedance (4 - 32 Ω) dynamic stereo headphones
Power Requirement:  100 V; 117 V; 220 V; 240 V, 50/60 Hz
Power Consumption:
70 watts at zero signal output
375 watts at rated power output into8 Ω load
Semiconductor Complement:  36 Transistors, 34 Diodes
Dimensions (W x H x D):  445 x 152 x 355 mm (17 ½" x 6" x 14")
Weight:  19,5 kg (42,9lbs) net

Accuphase C-200

 A good control center must be able to preamplify program source signals faithfully without changing their characteristics. It must also be able to provide compensation, when required, for room acoustics or deficieciesin program source signals. To satisfy the first requirement of fidelity, a good control center must have excellent characteristics such as wide dynamic range, flat frequency response, low noise and low distortion as well as the ability to amplify and deliver a true replica of the input pulse signal. As for its second function of supplying compensation, it must have excellent equalization and other circuitry that can be finely adjusted, as well as efficient filters to cut off noise.
Moreover, a good control center must have plenty of input connectors, and its controls should be well laid out to avoid complexity.
Accuphase C-200, which was designed to serve as a top class control center, easily meets all these requirements, and more. Every stage is push-pull driven and powered by dual power supplies. Input voltages up to 400 mVrms can be handled, a maximum for equalizer amplifiers. Its 10 inputs and 7 outputs, and a total of 28 controls attest to its functional diversity. Yet it is simple to operate. Excellent design and full utilization of its front and front-sub panels have made this possible.

Originality Marks Equalizer Circuitry
A) Differential amplification push-pull circuitry throughout Direct-coupled, complementary symmetrical circuit in every stage assures very excellent fidelity and outstanding stability.
B) Easily handles dynamic range inputs.
Employment of complementary-symmetry Class A driver amplifier in the final stage and use of plus, minus dual power supplies enable the C-200 to handle wide dynamic range inputs as large as 400 mVrms at1kHz with distortion ratio less than 0,05%. This rating applies with the equalizer amplifier gain set at 40 dB. If it is set to 30 dB, input voltages up to 1,2 Vrms can be handled.
C) Low enhancement circuit has fine adjustment of "presence"
The C-200 is equipped with a Low Enhance switch which accentuates rich bass tones that add to music enjoyment. This switch offers selection of 0, +0,5 and +1 dB change against the RIAA characteristic curve at 100 Hz.
D) Disc input level control has 10 dB variation.
A 10 dB continuously variable attenuator is available to attenuate cartridge output, when excessive, to a siutable level. It also permits comparison of cartridges connected to Disc 1 and Disc 2, and equalization of their levels.
E) Disc input has impedence matching switch.
The C-200 is equiped with an impedance matching switch which provides selection of 30 K, 47 K and 100 Kohms  input impedances at Disc 1. This makes impedance matching easy, especially to moving coil cartridges connected through step-up coupling transformers that require different optimum impedances depending on the make. It eliminates mismatching impedances  at disc input connections which deteriorate sound quality.
F) Subsonic filter prevents intermodulation distortion.
Sunsonic vibrations of the turnntable motor, etc., when playing records,should be cut before they can enter the input since they may otherwise cause intermodulation distortion. The C-200 has a subsonic filter that provides this sharp cut-off at 25 Hz.

Wide Choice of Tone Variation
A) 10-step bass control, plus two turnover frequencies.
Every shade of bass tone variation is at your fingertips with the C-200 which offers 10-step rotary switch control for each channel, plus a choice of 200 Hz or 400 Hz turnover frequencies. These turnover frequencies provide a variation range of ±10 dB (at 100 Hz for 400 Hz turnover, at 50 Hz for 200 Hz turnover).
B) 10-step treble control, plus two turnover frequencies.
Likewise every shade of treble control is also available through 10-step selection for each channel, plus choice of 2,5 kHz and 5 kHz turnover frequencies that provide a variation range of ±10 dB (at 10 kHz for 2,5 kHz turnover, 20 kHz for 5 kHz turnover).
An independent switch is provided to turn the tone control circiut ON or OFF.
 Low and High Filters
A) low Filter with 18 dB/oct cut-off at 30 Hz
The C-200 has a built-in low filter which can cut off at 18 dB/oct, all subsonic vibrations below 30 Hz which are likely to cause intermodulation distortion.
B) High Filter With 12 dB/oct cut-off at 5 kHz
It also has a 12 dB/oct cut-off High Filter for 5 kHz which very effectively cuts frequency noise without essentially affecting music quality.

Plenty of Input/Output Connectors
A total of 10 inputs and 7 outputs are available which should meet the needs of any assortment of program sources or sound equipment test connections. Of these, 3 inputs Mic, Aux and tape Play, and three outputs, Tape rec, Main Output, and headphone are conveniently available on the front sub-panel

Three tape Recorders Can be Connected
Inputs and outputs for connecting three tape recorders are available, of which two can be used for tape copying from one tape deck to the other. This function can be carried on while simultaneously listening to a different program source, since an independent tape copy switch is provided.

Complementary-Symmetry Circuit Headphone Amplifier.
A direct-coupled, complementary-symmetry circuit amplifier, made available exclusively for headphone use, upgrades the quality of headphone reproduction that is available through the C-200.

Well Regulated Power Supply
The well-regulated power supply is fully capable of supplying steady, non-fluctuating voltages to all amplifier stages and it is totally unaffected by any kind of input signal. This power supply is also capable of well-regulated performance even against reasonable AC line voltage fluctiations.

Speaker Switching Through Optional Relay Box.
In installations wher the power amplifier may not be close at hand, speaker selaction is possible through the C-200's front panel Speaker Selector switches when a Relay Box (optional ) is connected.

Frequency Response:
High level Input : 20 - 20,000 Hz (+0; -0,2 dB)
Low Level Input : 20 -20,000 Hz (+0,2; -0,2 dB)
Distortion:  Lower than 0,05% at rated output level 20 - 20,000 Hz
Input Sensitivity / Impedance:
Disc 1 ; 2-6 mV / 30, 47, 100 kΩ
Disc 2 : 2-6 mV / 47 kΩ
Mic. : 2 mV / 47 kΩ
Tuner : 200 mV / 130 kΩ
AUX 1 and 2 (front) : 200 mV / 130 kΩ
Tape Play 1 and 2 (front) : 200 mV / 130 kΩ
Maximum Input For Disc Input
400 mV RMS at disc level control miximum for 1 khz
1,2 V RMS at disc level control minimum for 1 khz
400 mV - 1,2 Vrms distortion ),05% at 1 kHz
Output Level and Impedance:
Main Output : 2,0 V / 200 Ω
Headphones : 0,4 V / 0,3 Ω
Tape Rec 1 and 2 (front) : 200 mV / 200 Ω
Mono Output : 0,42 V / 38 kΩ
Maximum Output Level:  10 Volts at 0,5% distortion
Voltage Amplification (in decibles)
Tuner, Aux, Tape Play Input :
20 dB to Main Output
0 dB to Tape Rec
6 dB to Headphones
Disc 1, Disc 2, Mic Input (at 1kHz):
60 dB to Main Output
40 dB to Tape Rec
46 dB to Headphones
Hum and Noise
Tuner, Aux, Tape Play :  90 dB below rated output
Disc , Mic. : 74 dB below 10 mV input
Bass Tone Controls:
Turnover Frequency 400 Hz : ±10 dB (2 dB step) at 100 Hz
Turnover Frequency 200 Hz : ±10 dB (2 dB step) at 50 hz
Treble Tone Controls:
Turnover Frequency 2,5 kHz : ±10 dB (2 dB step) at 10 kHz
Turnover Frequency 5,0 kHz : ±10 dB 92 dB step) at 20 kHz
Disc Low Enhancement (for Disc input):
0 dB, +0,5 dB, +1 dB at 100 Hz to RIAA standard characteristics.
Bass tone becomes richer when switched to =0,5 dB or 1 dB
ON position boosts low frequencies for low level listening.
+9 dB at 50 Hz (at volume control -30 dB)
Disc Subsonic Filter : 25 Hz cutoff 6 dB/oct
Low Filter : 30 Hz cutoff 18 dB/oct
High Filter : 5 kHz cutoff 12 dB/oct
Volume Control:  Less than 1 dB tracking erroe control down to -60 dB.
Power Requirement:  Voltage selector for 100, 117, 220, 240 V 50/60 Hz operation
Power Consumption:  36 Watts
Semiconductor Complement:  80 Transistors, 35 Diodes
Dimensions (W x H x D):  445 x 152 x 355 mm (17½ x 6 x 14 inches)
Weight:  14 kg ( 30,8 lbs) net