Modify from classic Marantz 7 preamp, circuit using two 12AX7 and one 12AU7, to lower the output impedance, a cathode follower is used.
A tube high voltage regulator and rectify using 5687
a time delay circuit, a heater voltage regulator using LM317,Analog section up-grade toGerman made GAD coupling capacitor,RA metal film resistor. (tubes are not included )
board size: L 280mm X W 200mm
(case and power transformer not included)