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

Onkyo TX-850

Important Features:
Discrete Output Stage:
Instead of IC power amp circuitry, the TX-850 both employ a discrete output stage for effortless drive into low impedance loads. Low distortion linear switching and the high quality parts used throughout are proof of Onkyo's dedication to audio excellence not merely in its high end amps but across the board.
"CD Direct" Switch:
This switch lets the user bypass the tone and balance controls in the amplifier when listening to CD (or other digital audio sources).since noise levels in digital audio are extremely low, sending and switching the audio signal through tone and balance circuitry is often unnecessary and may even adversely alter the high quality digital signal.
APR (Automatic Precision Reception) System:
Onkyo's exclusive APR precision reception system lets every FM broadcast sound its best. Intelligent circuitry monitors the signal and selects the optimum settings for three reception modes: stereo/mono, hi-blend on/off and local/DX mode, the system controls the noise reduction on/off mode as well.  The APR system settings are shown by indicators on the front panel.
Other Features:
20-station FM/AM Random memory with Battery Free Backup
Full Logic Selector Keys for Seven Input Sources Including Video Input and Dubbing Capabilities
Dynamic Bass Expander and Stereo Image Expander
Selective Tone Control
Sleep Timer (max. 90 minutes, also operable via remote control)
Simulated Stereo
Remote Controlled Motor Driven Volume Control
System Remote Control Possible with Onkyo Components

Amplifier Section
Power Output:  68 watts per channel, min. RMS, at 8 Ω both channels driven, from 20 Hz to 20 kHz with no more than 0,04% T.H.D.
Total Harmonic Distortion:  0,04% at rated power
IM Distortion:  0,04% at rated power
Damping Factor:  40 at 8 Ω
Frequency Response:  20 - 30,000 Hz ±1 dB
RIAA Deviation:  20 - 20,000 Hz ±0,8 dB
Sensitivity and Impedance:
Phono :  2,5 mV/ 50 k Ω
CD/Tape Play :  150 mV/50 k Ω
Tape Rec :  150 mV/ 3,5 k Ω
Phono Overload:   120 mV RMS at 1 kHz, 0,04% T.H.D.
Signal-to-Noise Ratio:
Phono :  85 dB (at 10 mV input, A weighted);  75 dB (IHF-A 202)
CD/tape :  85 dB (A weighted);  80 dB (IHF-A  202)
Tone Controls:
Bass :  ±10 dB at 100 Hz
Treble :  +_10 dB at 10 kHz
FM Tuner Section:
Tuning Range:  87,9 - 107,0 MHz (200 kHz steps) and/or 87,5 - 108,0 MHz (50 kHz steps)
Usable Sensitivity
Mono :  10,8 dBf (1,9 µV)
Stereo :  17,2 dBf (4,0 µV)
50 dB Quieting Sensitivity
Mono :  17,2 dBf (4,0 µV)
Stereo :  37,2 dBf (40 µV)
Capture Ratio:  1,5 dB
Image rejection ratio:  40 dB
IF Rejection ratio:  90 dB
Signal-to-Noise Ratio: 
Mono :  73 dB
Stereo :  67 dB
Alternate Channel Attenuation:  55 dB
AM Suppression Ratio:  50 dB
Harmoni Distortion:
Mono :  0,15%
Stereo :  0,25%
Frequency Response:  30 - 15,000 Hz ±1,5 dB
Stereo  Separation:  45 dB at 1 kHz; 30 dB at 100 - 10,000 Hz
Muting Level"  17,2 dBf (4 µV)
AM Tuner Section
Tuning Range:  530 - 1620 kHz (10 kHz steps) and/or 522 - 1611 kHz (9 kHz steps)
Usable Sensitivity:  30 µV
Image rejection ratio:  40 dB
IF Rejection ratio:  40 dB
Signal-to-Noise Ratio: 40 dB
Harmonic Distortion:  0,7%
General Section
Power Supply:  AC 120V, 60 Hz and/or 120V and 220 V switchable, 50/60 Hz
Dimensions (W x H x D):  435 x 130 x 351 mm (17-1/8" x 5-1/8" x 13-13/16")
Weight:  8,8 kg 919,4 lbs)

Remote Control (RC-118S)

Marantz SR-50L

 Stereo Receiver with Digital AM/FM Stereo Tuner
FM Tuner Section
Frequency Range:  87,5 - 108 MHz
Sensitivity DIN (Mono/Stereo):  1,2 / 25 µV
Signal-to-Noise  Ratio (Mono/Stereo):  76 / 68 dB
Total Harmonic Distortion : 0,2/0,4 %
Selectivity at 98 MHz (± 300 kHz):  60 dB
MW Tuner Section
Frequency Range:  531 - 1602 kHz
Sensitivity (S/N  20 dB 30% 1 MHz):  500 µV
Signal-to-Noise Ratio at 1 MHz:  50 dB
LW Tuner Section
Frequency Range:  152 - 282 kHz
Sensitivity (S/N 20 dB 30% 1 MHz):  1000 µV
Amplifier Section
Power Output
DIN at 8 Ω  :  50 W
RMS at 8 Ω  :  40 W
Total Harmonic Distortion (at 8 Ω rated RMS output):  0,09%
Damping Factor:  50
Input Sensitivity
Phono :  3,5 mV/47 k Ω
CD, Tape, CDV, VCR :  220 mV/47 k Ω
Signal-to-Noise Ratio (IHF-A):
Phono :  76 dB
CD, Tape, CDV, VCR :  86 dB
Power  Supply:  AC 220V 50/60 Hz
Dimensions (W x H x D):  420 x 118 x 334 mm
Weight:  6,5 kg

Supplied Accessories:  Remote controller RC-60SR

Audio Research SP11

 The SP11 is a hybrid unit, utilizing both vacuum tubes and FETs (Fiel Effect Transistors). It is not intended that this product should somehow continue the controversy of "vacuum tubes" vs. "solid-state". Rather, in keeping wit Audio Research's design philosophy of advancing the state-of-the-art., each type of device is used where it performs best.
One important result, aside from the dramatically improved quality of sound reproduction, is the use of only six vacuum tubes - tubes which need not be selected low-noise types. A significantly longer time between tube replacement is also expected.
As a last word, this preamplifier may well change your thinking about music reproduction. Because it is so incredibly "open" sounding, much information not previously sudible is available, providing new insight and enjoyment from many sound sources. To be appreciated, the SP11 preamplifier must be personally experienced; it cannot otherwise be adequately related.
 Operational Features:
Automatic warmup, brown-out power-line interruption muting and manual muting at all preamplifier outputs, with new shunt circuitry.
Subsonic phono filter with 6 dB /oct rolloff (to eliminate ringing) with transition to 12 dB/octave.
Bypass switch for use with "audiophile quality" program material.
Absolute phase switch for main outputs, plus unswitched inverting and non-inverting outputs.
Full tape functions; two inputs, two recording outputs, plus tape copy and tape monitor functions.
Input/output connectors have heavy gold plating and connect "ground" before "hot".
Level set control in addition to normal gain control. Allows essentially unlimited input signal range while preserving optimum gain control usage.
Toroid power transformer for low mechanical noise and low external magnetic field.
 In Octobr of 1985, Audio Research Corporation introduced the SP11 preamplifier. During the first year, our introductory claim of "a new reference standard" has been confirmed by reviewer after reviewer throughout the Free World.. It is improbable that any audio product, including previous Audio research products, has ever received such unanimous acclaim. We believe that once you hear the SP11 reproduce music, you will find that acclaim justified.

Frequency Response:
High Level Input :  0,2 Hz to 100 kHz ±1 dB (-3 dB below 0,1 Hz and above 200 kHz)
Phono Input:  20 Hz to 40 kHz ±2 dB of RIAA (±1 dB of RIAA, 1,0 Hz to 100 kHz)
Harmonic Distortion:  less than 0,005% at 2 V RMS output, 5 Hz to 20 kHz (Typically less than 0,001% at midband, phono or line input)
Intermodulation Distortion:  less than 0,003% at 2 V RMS output
Gain (aat 1 kHz , bypass mode):
Phono Input to Tape Output :  46 dB (0,2V output from 1mV input)
Phono Input to Main Output :  75 dB (0,175 mV input for 1 V output)
High Level Input to Main Output :  29 dB (36 mV input for 1 V output)
Inputs:  Phono, Tuner, CD, Video, Spare, Tape 1, Tape 2,
Outputs:  Tape 1, Tape 2, Main 1, Main 2, Direct, Invert
Filter:  25 Hz Hi-pass phono subsonic 6 dB/octave rolloff (to eliminate ringing) with transition to 12 dB/octave at 10 Hz. Front panel switchable, phono only
Controls:  Gain, level (to set gain Range), balance, Mode, Input, Impedance
Switches: Tape Monitor, Copy, Tape 1/2, Tape 1 to 2/2 to 1, Mute, Invert Phase,Bypass, Filter
Input Impedance:
Phono :  47 k Ω, 100, 30, 10, 3 Ω (front panel selectable)
Phono Input Capacitance:  150 pF at 10 kHz
High Level:  20 k Ω or higher, depending on switch functions
Maximum Inputs Level Undistorted:
Phono :  350 mV RMS at 1 kHz, 1200 mV RMS at 10 kHz (0,1 second maximum duration, 6 dB less if continuous)
High Level :  25 Volts RMS
Output Impedance:  250 Ω main, direct, invert outputs, 500 Ω tape output. Recommended load 60 k Ω and 100 pF (25 k Ω minimum, 1000 pF maximum)
Rated Output:  2V RMS 1 Hz to 100 kHz main, direct, invert outputs (Maximum 80 V RMS output at 0,2% T.H.D. at 1 kHz into 60 k Ω load with 2,85 V RMS high level input)
Tape Outputs, Direct Output;  Non-inverting
Invert Output :  Inverting
Main Outputs :  selectable non-inverting or inverting. All outputs may be used simultaneously.
Noise (IHF Weighted, shorted input):
Output (Gain down) :  6 µV (110 dB below rated output)
Input High Level) :  3 µV equivalent input (110 dB below 1 V input)
Phono :  0,15 µV equivalent input (76 dB below 1 mV input)
Tube Complement (Hybrid FET/Tube Audio Circuit, Solid-State Power Supply):  6 - 6DJ8/ECC88
Power Requirements:  95 - 135 V AC 60 Hz (Export 190 - 270 v AC 50/60 Hz)
Power Consumption:  130 watts maximum
Dimensions (W x H x D) Each Chassis, EIA Rack panel Mounting:
480 x 134 x 260 mm (19" x 5,25" x 10,25")
Weight Net:
SP11 :  6,4 kg (14 lbs)
SP11PS :  6,8 kg (15 lbs)  

Audio Research M300

M300 Hybrid Monaural Power Amplifier - Audio Research Corporation developed and patented new circuitry allowing hybrid utilization of Fets with vacuum tubes in ways which can bring out the best in both devices. This circuitry is used in the relatively new, but already widely-acclaimed SP-11 preamplifier. Drawing from this technology, Audio Research has designed a new hybrid power amplifier, designated the M300 - a monaural unit rated at 300 watts.

Hybrid Monaural Power Amplifier
Most hybrid power amplifier designs use small signal-input vacuum tubes, then rely on FETs for the output stage. Audio Research has chosen instead to eliminate these low-level input tubes - tubes which can be prone to problems with hum, noise, microphonic, drift and, of course, require periodic replacement. The new FET "front end" is combined with Audio Research's long-famous, patented cross-coupled circuit to provide a design offering exemplary stability, reliability (low maintenance), and superior performance.
These design advances have been coupled with yet another Audio Research patent; an output stage utilizing vacuum tubes, and partially cathode-coupled (as all previous Audio Research vacuum tube amplifiers have ben), but with the screen (or accelerating) grids operating with a signal voltage precisely in phase with the cathode voltage. True "pentode" operation and efficiency is thereby achieved; however, all thr advantages of partial cathode coupling are maintained .
Advantages include:
Efficiency up to 60% above. (Class "A" designs achieve 25% to 50% typically 30% to 35%)
Inherently better cross-coupling
Output transformer with lower "turns" and "impedance" ratios, resulting in greater bandwidth.
Partial cancellation of saturation effects of the "DC" inn the output transformer's core
Switching transients essentially eliminated, rendering the question of class of operation ("A", "AB", etc.) irrelevant. The virtues of Class "A" operation without the usual drawbacks
Bias adjustment is essentially non-critical.
Output tubes need not be matched, although slighty better performance will result if they are.
Lower internal impedance improves handling of complex speaker loads.

Operationsl Features:
Front-panel replaceable line and screen voltage fuses, with LED indicators.
Two integral, low-noise fans for cooler operation, longer tube life. Front-panel switch allows "Hi" and "Lo" speeds.
"Standby" switch for lower power consumption and less heat during warm-up periods or telephone interruptions.
Automatic muting circuit provides silent shutdown upon power shut-off or interruption. No "thump" from speakers.
Gold-plated input connectors connect "ground" before "hot".
1, 2, 4 and 8 ohms output taps.
Front and rear handles for easier handling

Tube Saver protection Circuit
The M300 Power amplifier contains a remarkable new circuit called the :Tube Saver" it's a small secondary circuit board located on the back side of the main board in the amplifier. Primarily, the "Tube Saver" reduces stress to tubes and associated driving Fets. As an overload protection circuit, it is triggered only when abnormal current is sensed from a cause like those listed  below. Under even extreme conditions of normal use (i.e. extremely high playback levels), the circuit is designed to remain inactive. When triggered, the circuit immediately shuts down th eoutput stage and indicates protection mode by dimming the "Screen" LED. At this point, the amp should be manually switched off, then restarted after a period of 30 seconds.

Power Output:  300 watts minimum continous at 8 Ω, from 16 Hz to 25 kHz with less than 0.5% T.H.D. (typically below .005% at 1 watt).
Approximate Actual Power Available at Clipping:  330W at 1 kHz, nominal.
Power Bandwidth:  10 Hz - 60 kHz (-3 dB Points)
Input Sensitivity:  1,5 V RMS for rated output
Input impedance:  60 k Ω, nominal
Output Regulation:  Approx. 0,3 dB, 8 Ω load to open circuit (Dampping factor approx. 30)
Negative Feedback:  20 dB
Slew Rate: 25 volts/microsecond
Rise Time: 3 microseconds
Hum and Noise: less then 2 mV RMS 90 dB below rated output (broad-bandwidth unweighted, inputs shorted)
Power Supply Energy
Storage:  approx. 350 joules
Power Requirements:  105 - 125 V AC 60 Hz (210 - 250 V  AC 50 Hz); 900 watts at rated output, 450 watts at "idle" - 130 watts at "standby"
Dimensions (W x H x D):  480 x 270 x 410 mm (19" x 10,5" x 16")
Weight:  50 kg (110 lbs) net

Tubes required:  8 - 6550 Power Output (matched pairs will yield marginally better performance)