I wired up the rectifier socket, complete with safety diodes to protect the PT in case of shorted tube, and a 2-phase solid state rectifier (which is just a pair of additional diodes), connected to a switch so that I can easily switch between tube-rectified and diode-rectified voltage. The rectifier takes high voltage AC current and converts it to high voltage DC that can be used by the power tubes and pre-amp tubes to amplify the signal at various stages in the signal path. In my case, the PT is generating 350VAC, which will be converted to something between 400 and 450VDC for tube rectification (with different tube types generating different output volts) and 455 to 465VDC for solid state rectification. The layout snippet will put the second picture in context.
(Rectifier layout)
I also wired up the heaters to all the tube sockets (tubes use filament-type heaters, like an incandescent lightbulb, to free up electrons that then flow from cathode to plate). For a number of reasons:
- because we don't want heavy AC current traveling in wires near to the delicate low voltage signal
- wires, which can pick up the noise
- and because of the closeness of the pre-amp tubes to each other and to the circuit board,
- and the way the signal wires come from underneath the board, right down against the chassis
- and also because I just wanted to try different things
... I used two different methods to wire the heaters, both common practice though some folks claim one or the other method to be superior. In the case of the power tubes, I laid the twisted heater red and black wires (stranded #18) down on the chassis at the back and came forward to the tube sockets in linear fashion. For the pre-amp tube heaters I used blue solid core wire (which keeps its shape and stays where you put it space), following the same route at first, but then went skyward and arced up and down into each socket. Both methods keep the heater wires as far away from signal wires as possible, and/or on dissimilar axes, to prevent noise induction from the electromagnetic field created in the wires.
