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 C-27

 McIntosh model C 27 preamplifier features:
You Choose From Seven Different Program Sources.  The input switch selects from five different sources or you can choose to listen to either of two tape recorders at the push of a button.
You Always Get The Ideal Stereo Image. The McIntosh seven position mode selector has facilities to permit the proper balancing of a stereo system to maximize stereo imaging. It assists in easily restoring proper stereo perspective should you play an improperly made recording.
Tape Recording and Playback Made Easy. Tape input, tape output and switching facilities are provided for two three-head tape recorders. Simply push a button to listen to either one - or record from any selected source on either or both - or - copy from one tape recorder to another while listening to an entirely different program. You can instantaneously monitor either tape recorder.
Listen To Your Quiet records, Quietly. Any unwanted noise (hiss, rumble, fry, etc.) can be reduced with the four position filter switch. It alows the removal of low frequency noise, high frequency noise or both yet retaining as much of the wanted program as possible.
 Control Remote Loudspeakers From Your Preamplifier. Through a unique McIntosh design, interconnecting the preamplifier and power amplifier, you have On/Off control of two separate sets of stereo speakers. Another advantage of this unique design is the ability to plug your headphones into a front panel jack for private listening.
Stepped Tone Controls Independent In Each Channel> settings are precise and repeatable in each channel, independently. Each tone control is a separate eleven position switch concentrically mounted. Each step is connected to carefully selected resistors and capacitors to give the precise frequency curve shape. Because the tone circuit component parts are not in contact with the switch surfaces, as in ordinary continuously variable rotary controls, they never change, never get noisy and provide exact, repeatability settings.
You Can Listen at Low Volumes With Equal Pleasure. A continuously variable loudness control lets you enjoy full frequency reponse and warmth of music regardless of the room volume you choose. As volume is reduced, the frequency response is adjusted to complement the human ear response characteristics, the Fletcher Munson effect.
 The Constant Loudness Balance Control. The McIntosh balance control adjust each channel independently for proper stereo imaging without a modification of overall stereo volume in the room. While natural balance is at the center of the control; adjustment to either right or left compensates for program variations or room acoustic differences.
Precision Step Attenuator Volume Control. Ideal volume control tracking accuracy and noise free performance are two of the considearable benefits of the McIntosh Precision Step Attenuator. It is a thirty-two step, 70 dB range control with unheared of tracking accuracy within 1 dB. The extreme accuracy is obtained through special electronically controlled resistance element trimming. The accuracy and quiet operation are maintained because the switch commutator touches only the switch contact pad and not the precision resitor elements.
Frequency Response:  20 Hz - 20 kHz (+0 -0,5 dB)
Harmonic Distortion:  will not exceed 0,05% (at rated output 20Hz-20kHz)
Hum and Noise: 
Phono 1, 2 :  80 dB below 10 mV input (unweighted); 85 dB IHFA (weighted)
Tuner, Aux, Tape 1,2 :  85 dB (unweighted); 90 dB IHF A(weighted)
Input Sensitivity/Impedance:
Phono 1, 2 :  2 mV/47 k Ω and 100pF
Tuner, Aux, Tape 1,2 :  250 mV/100 k Ω
Output Level/Impedance:
Main Output :  2,5 volts with rated input, less than 1 k Ω source impedance (max. output is greater than 10 volts)
Tape Output :  2,5 volts with rated input, less than 1,5 k Ω source impedance (max. output is greater than 10 volts)
Center Channel Output (L+R) :  2,5 volts with rated input to both channels, less than 1,2 k Ω source impedance, to operate into 22 k Ω load or higher
Voltage Amplification In Decibels:
Phono 1, 2 :  to Main Output 62 dB; to Tape Output 42 dB
Tuner, Aux tape 1, 2 :  to Main Output 20 dB; to Tape Output 0 dB
Tone Controls:
Bass :  -17 dB to +16 dB at 20 Hz (Separate 11 position rotary switches for each channel)
Treble :  -20 dB to +20 dB at 20 kHz (Separate 11 position rotary switches for each channel)
Filter Switch:
Low Frequency (Rumble Filter):  Flat or roll-off 6 dB per octave below 50 Hz, down 12 dB at 20 Hz
High Frequency (Scratch Filter) : Flat or roll-off 6 dB per octave above 5 kHz, down 12 dB at 20 Hz
Semiconductor Complement:  18 Silicon-Planar transistors; 4 Silicon diodes; 5 Light Emitting diodes (LED)
AC Power Outlets:  4 switched and 1 unswitched (red)
Power Requirements:  120 volts 50/60 Hz
Power Consumption:  15 watts
Dimensions (W x H x D):
Chassis ;  375 x 122 x 330 mm (14-3/4" x 4-13/16" x 13")
Front Panel :  406 x 138 mm (16" x 5-7/16")
Net :  9,1 kg (20 pounds)
Shipping :  14,5 kg (32 pounds)
Finish:  Front panel is anodized gold and black with special McIntosh gold/teal panel nomencalture illumination. Chassis is black

Mounting:  exclusive McIntosh developed professional Panloc

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