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Below is a circuit for a magnetic phono (turntable) pre-amplifier. You will need two identical circuits for stereo, one for each channel.
Since this is a pre-amplifier amplifying very low signal levels, you should use DC voltage for the filaments. Output of this pre-amplifier is
high impedance and must connect to a high inpedance input such as a vacuum tube amplifier. Also, cable length between the
pre-amplifier output and the amplifer it connects to should be 3 feet or shorter. A 6 foot cable can be used but there may be some
high frequecy loss. As with most high gain tube amplifiers, some tubes may pick up microphonics from vibrations. Placing the pre-amplifer
on a foam pad should isolate vibrations. Be sure to include a bottom plate that covers the chassis underside. Besides shielding, it
prevents fingers from touching the 120VAC or 370VDC supply. |
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Includes chassis |
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Underside of |
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Power supply |
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Completely wired |
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PARTS LIST 1 - 7" X 5" X 2" CHASSIS - ALLIED ELECTRONICS STOCK NUMBER 806-3030 1 - 7" X 5" CHASSIS BOTTOM PLATE - ALLIED ELECTRONICS STOCK NUMBER 806-1403 1 - POWER TRANSFORMER 6K1VF - ALLIED ELECTRONICS STOCK NUMBER 227-0001 2 - 9-PIN TUBE SOCKET - TRIODE ELECTRONICS or PARTS EXPRESS > - be aware that some sockets require a 3/4 inch hole and some require a 7/8 inch hole 2 - 12AX7A VACUUM TUBES - TRIODE ELECTRONICS or PARTS EXPRESS 3 - GROMMETS - ALLIED ELECTRONICS STOCK NUMBER 839-0421 1 - AC CORD - ALLIED ELECTRONICS STOCK NUMBER 592-2235 1 - FUSE HOLDER - ALLIED ELECTRONICS STOCK NUMBER - 740-0634 1 - 1/4 AMP SLOW BLOW FUSE - ALLIED ELECTRONICS STOCK NUMBER 740-0732 1 - OPTIONAL POWER SWITCH - ALLIED ELECTRONICS STIOCK NUMBER 870-0555 1 - 100 VOLT 4 AMP BRIDGE RECTIFIER - ALLIED ELECTRONICS STOCK NUMBER 266-0032 1 - 800 VOLT 4 AMP BRIDGE RECTIFIER - ALLIED ELECTRONICS STOCK NUMBER 266-0035 4 - RCA JACK ASSEMBLY - ALLIED ELECTRONICS STOCK NUMBER 932-0256 6 - 8 TERMINAL STRIP - CINCH 56C - ALLIED ELECTRONICS STOCK NUMBER 750-6636 1 - 3 TERMINAL STRIP - CINCH 52A - ALLIED ELECTRONICS STOCK NUMBER 750-6621 NOTE - USE CARBON COMPOSITION RESISTORS IN HIGH VOLTAGE CIRCUITS 4 - 2.7K 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-2.7K 2 - 15K 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-15K 2 - 22K 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-22K 2 - 39K 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-39K 4 - 100K 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-100K 2 - 470K 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-470K 2 - 680K 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-680K 1 - 1M 1/2 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 30BJ500-1.0M 1 - .68 OHM 5 WATT RESISTOR - MOUSER ELECTRONICS STOCK NUMBER 280-CR5-0.68-RC 1 - 6K 3 WATT RESISTOR - ALLIED ELECTRONICS STOCK NUMBER 296-5174 2 - 180PF 500V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 5982-15-500V180 2 - .0033MFD 600V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 75-715P600V0.0033 2 - .01MFD 400V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 75-225P400V0.01 2 - .1MFD 400V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 75-225P400V0.1 2 - .22MFD 400V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 75-225P400V0.22 4 - 22MFD 50V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 647-TVX1H220MAD 3 - 10MFD 450V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 647-TVX2W100MCD 1 - 47MFD 400V CAPACITOR - ALLIED ELECTRONICS STOCK NUMBER 613-0252 2 - 10,000MFD 16V CAPACITOR - MOUSER ELECTRONICS STOCK NUMBER 647-UHE1C103MHD WIRE AVAILABLE FROM ALLIED ELECTRONICS 26 GAUGE WIRE BELDON 600V TEFLON INSULATION STOCK # 214-1082 - BLACK 214-1083 - RED 214-1084 - GREEN 214-1085 - YELLOW 26 gauge wire can be used for all wiring in the phono pre-amplifier including filaments. HARDWARE 4 - 4-40 X 1/4" SCREWS, NUTS AND LOCKWASHERS 1 - 6-32 X 1/2" SCREW, NUT AND LOCKWASHER 13 - 6-32 X 1/4" SCREWS, NUTS AND LOCK WASHERS |
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vacuum tube related TONE CONTROLS MAGNETIC PHONO PRE-AMPLIFIER AUDIO CONTROL CENTER LEVELING AMPLIFIER CLASSIC BASS REFLEX SPEAKER |
solid state related TRANSISTOR AMPLIFIER STAGE TRANSISTOR AMPLIFIER 2-STAGE TRANSISTOR 10 WATT AMPLIFIER |
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vacuum tube related BASIC ELECTRONICS BUILDER TIPS THE VACUUM TUBE THE TRIODE AMPLIFIER VACUUM TUBE POWER SUPPLY USING A SOILD STATE SUPPLY SELECT A POWER TRANSFORMER FILAMENT DC SUPPLY CALCULATE FUSE SIZE TUBE DATA SELECTING WIRE SIZE |
general LETTERING A PANEL GROUND LOOPS BALANCED AUDIO LINES |
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WBBM Chicago, Illinois WEZW Milwaukee, Wisconsin WFUN Miami, Florida WROK-AM, WZOK-FM Rockford, Illinois |
EXPERIMENT THAT SAVED HI-FI RUSSELL O HAMM PAPER ANALOG~DIGITAL AUDIO EAR DAMAGE - LOUD AUDIO SOUND ON FILM REBUILDING A HOLMES 35MM PROJECTOR SAENGER THEATER, MOBILE, ALABAMA |