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MC INTOSH C20
Stereo tube preamplifier
Early version
FRONT PANEL : anodized gold and black crystal. Upper line : Mode selector (rev / stereo / L / R / m left / m right) - Balance - Phase (0° - 180°) HF cut-off filter ( flat / 9 KC / 5 KC) Aural comp (flat 5) Volume. Lower line : input selector (aux- tape- tuner 1- 2 phono 1 stereo/mono phono 2 stereo/mono tape hd 1-2). Record compensator : bass treble. Bass and treble controls. Rumble tape jack tape compare push-buttons. Tape jacks. PANNELLO FRONTALE : in anodizzato oro e cristallo nero. Linea superiore : Mode selector (rev / stereo / L / R / m left / m right) - Balance - Phase (0° - 180°) HF cut-off filter ( flat / 9 KC / 5 KC) Aural comp (flat 5) Volume. Linea inferiore : input selector (aux- tape- tuner 1- 2 phono 1 stereo/mono phono 2 stereo/mono tape hd 1-2). Record compensator : bass treble. Controlli bass e treble. Pulsanti rumble tape jack tape compare. Ingressi tape.
Later version No anodized bar in the middle line. Loudness term substitutes aural comp. Ultima versione : assenza della barra centrale in anodizzato. Dicitura Loudness anzichι Aural comp.
REAR PANEL. In the upper line : main output, tape output, left and right low frequency trim inputs (tape monitor,aux,tape,tuner 1,tuner 2). In lower line: 4 AC outlet (1 unswitched for tape machine or turntable, colored red; 3 switched, colored black- total capacity 600 w max), Bright/Pilot/Dim selector, Phono 1 inputs ( xtal/ceramic low and high magnetic) Phono 2 inputs ( xtal/ceramic low and high magnetic), tape head 1 (low and high), tape head 2 (low and high).
PANNELLO POSTERIORE. Sul livello superiore : main output, tape output, left and right low frequency trim inputs (tape monitor,aux,tape,tuner 1,tuner 2). Sul livello inferiore : 4 prese di alimentazione AC (1 unswitched per tape o giradischi, colore rosso, 3 switched, colore nero - capacitΰ totale 600 w max), Bright/Pilot/Dim selector, Phono 1 inputs ( xtal/ceramic low and high magnetic) Phono 2 inputs ( xtal/ceramic low and high magnetic), tape head 1 (low and high), tape head 2 (low and high).
Top view
Top view open
Bottom view
SPECIFICATIONS (from the original Mc Intosh brochure)
Input Selector: Selects any one eight program sources including Tape, Tuner 1 and Tuner 2, Auxiliary, Phono 1 and Phono 2,Tape Head 1 and Tape Head 2. Each phono input has two switch positions, one for stereo the other parallels the stereo cartridge for Monophonic records. Mode Selector: Reverse: connects left channel to right speaker, right channel to left speaker, corrects for left-right reversal of program. Stereo: (normal Stereo mode selector position) left channel to left speaker, right channel to right speaker. Left: left channel to left speaker no program to right speaker. Right: right channel to right speaker, no program to left speaker. M Left: left channel only to both speakers. M Right: right channel only to both speakers. Record Compensator: Separate bass and treble compensator switches including " R I A A , " "LP," "Tape-Head," flat position for microphone and other positions for monophonic records. (Turning "TREBLE" control to "TAPE" gives flat response. Turning "BASS" to "O" gives flat response.) Tone Controls: Treble: boost 13 db at 20,000 cycles attenuate 18 db at 20,000 cycles. Bass: boost 16 db at 20 cycles, attenuate.20 db at 20 cycles. Balance Control: To balance for unequal program source: Turning control to left reduces right channel to No Output Turning control to right reduces left channel to No Output. Phase Control: Reverses phase in the left channel to correct for speaker or program phasing. HF Cut-off Filter: Three positions providing (1) no filter action for normal use, (2) 9 KC cut-off, and (3) 6 KC cut-off to suppress record noise and hiss. Loudness Control: Compensates for the Fletcher- Munson hearing characteristics as program loudness is reduced. Rumble Filter: Suppress low frequency disturbances such as rumble. Tape: Front panel jacks, push button switch controlled to permit the addition of a portable tape recorder without disrupting the equipment permanently installed. Tape Monitor: To permit instantaneous monitoring of tape before and alter recording. Low Frequency Trim Controls: On the back panel. Compensate for unequal response at low frequencies due to position of speakers or differences in speaker efficiency. Provides 6 db boost at 50 cycles starting from 500 cycles or 8 db cut at 20 cycles starting from 200 cycles.
CONTROLS Main Output: 2.5V with rated input 2 output jacks in parallel for each channel Tape Output: 0.25V with rated input 1 output jack for each channel - Left plus right output: 2.5 volts from source impedance of 23.000 ohms Voltage Amplification: Low level inputs to Main Output: 1,000 to 1 (60db) at 1000 cycles Low level inputs to Tape Output: 100 to 1 (40db) at 1000 cycles High level inputs to Main Output: 10 to 1 (20db) High level inputs to Tape Output: 1 to 1 (0db) Tape Monitor input to Main Output: 10 to 1 (20db) A.C. Aux. Outlets: 1 unswitched for tape machine or turntable. colored Red; 4 switched, colored Black Power Requirements: 117 volts 60 cycles A.C. 35 watts
MECHANICAL SPECIFICATIONS Size: 155/8" wide by 51/8" high. Overall depth of chassis behind front panel is 1213/16".. The space required in front of cabinet panel for the thickness of the panel and knobs is 1Ό". Weight: Chassis only 18 pounds. In shipping carton 28½ pounds.
ELECTRICAL SPECIFICATIONS Frequency Response: ±0.5 db 20 to 20,000 cycles Distortion: Less than 0.2% at rated output, 20 to 20,000 cycles Hum and Noise: High level inputs: 85 db below rated output Low level inputs: less than 2 microvolts et input terminals Input Sensitivity and Input Impedance: Auxiliary: 0,25 volts 470.000 ohms Tape: 0.25 volts 470,000 ohms Tuner 1: 0.25 volts 470,000 ohms Tuner 2: 0,25 volts 470,000 ohms Phono 1: 2 to 10 millivolts 47,000 ohms for low output cartridge 10 to 70 millivolts 47,000 ohms for hi output cartridge 0.1 volt 220 mmf in series with 47,000 ohms for Xtal or Ceramic Phono 2: Same as phono 1 Tape Head 1: 2 to 10 millivolts 47,000 ohms for low output head Tape Head 2 : Same as tape head 1 Tape Compare (Monitor): 0.25 volts, 115,000 ohms
Are available on request the owner's and service manual with schematics.
Sono disponibili a richiesta il manuale di istruzioni e di servizio con gli schemi.
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