C22 Preamplifier User Manual
Contents
1. C22 Vacuum Tube Preamplifier User Manual Analog Metric C22 VACUUM TUBE PREAMPLIFIER USER MANUAL Analog Metric Metric BILANA Aia ZZ yso u my pea I J tex ozy INTRODUCTION The circuit design is with referenced to the classical McIntosh C22 pre amplifier It uses three 12AX7 vacuum tubes for amplification and uses one pentode triode vacuum tube 6F3P 6BMB as voltage regulation Vishay 1N5062 forming a bridge provide for full wave rectification The resulted 300V DC A low dropout regulator LM1084 is used to supply the filament As all resistors and capacitors are low noise with good channel matching the sound quality should have low distortion FEATURES e Three vacuum tubes 12AX7 and one 6F3P 6BM8 amp ECL82 e Two single ended inputs and two single end outputs for stereo e Voltage gain 22dB e Dynamic range output voltage max 20Vrms e S N ration gt 90dB e Built in voltage regulation circuit e Optional mounting holes for delay protection module www analogmetric com Page 2 C22 VACUUM TUBE PREAMPLIFIER USER MANUAL Analog Metric Metric e Power requirements one 260V AC 200mA one 15V AC IA and one 6 3V AC 1A e PCB dimension 110mm W x 250mm L e PCB thickness 2 5mm double layer 20z copper PRECAUTIONS e Do not use finger or any body parts to touch the components or board It is hazardous since the high voltage capacitors may not be fully discharges after switc2. hed off the power supply e Turn off the power supply if the transformer is getting hot or some smoke is observed or strange buzz sound is heard e Fuse should be used either in power transformer or main socket to avoid accidentally large current drawing e Always contact technicians or experts to seek help PROCEDURES 1 Solder all the components according to the schematic part list and photos Notice to the polar ty of the high voltage capacitors and the direction of the Zener diodes 2 Either connect delay output protection module optional to the jumper J6 and J7 or short it 3 Connect the power transformer 280 300V AC 12 15V AC and 6 3V AC to the board without plugging the vacuum tubes 4 Measure the AC voltages at the connectors to see whether the voltages are maintained that are 280V AC 15V AC and 6 3V AC 5 If the voltages are correct plug in the tubes and turn on the main power 6 Good luck If you have any problem in assembly please contact us by email to tech analogmetric com www analogmetric com Page 3
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