I had built a capacitor multiplier for use in my Hiwatt Custom 50 amp. The idea was to reduce the 60 cycle hum it had. One of my frustrations with the task was how fussy the cap multiplier was to wire, and it looked uncomfortably homemade. I recently noticed that there is free software on the internet that allows one to design printed circuit boards (PCB) and have them built by prototype companies–I settled on KiCad as the design program.
The minimum PCB order quantity is three at oshpark. I ordered three PCBs from oshpark for $31 dollars, and received them today. I assembled one and and have been testing it on my bench. The first thing I did to verify my design was to assemble it according to the printing I put on it and see if the circuit is correct–it was. I would not have been surprised if something was wrong with my first try, and I was prepared to go through a few cycles of prototyping. A properly working design right out of the gate is on the high end of possible outcomes.
On the test bench I have around 500 volts going into it. I have a 1 watt (470k) resistor for a load and its drawing 1.1 ma. It has about 1.5 volts drop from in to out. Perhaps because the low is so low, its dramatically reducing the characteristic sawtooth wave that emerges from a linear high voltage guitar amp type rectifier and capacitor circuit. I note that sawtooth has some high frequency noise riding on it, not sure where that is coming from.
Since the power supply on my Hiwatt can emit in excess of 600 volts. Any apps using small size capacitors need two caps in series, as 400 volts is the voltage limit on readily available capacitors–500 volts is the general limit, and that does not allow for generous over-engineering to make it more reliable. I get my electronic parts from digi-key and mouser. The active device is a BUL416T NPN transistor which can handle 800 volts across its collector-emitter. These are made for fluorescent light ballasts and cost about $3.60 each.
I want to acknowledge Merlin Blencowe for his wonderful book “Designing Power Supplies for Valve Amplifiers” (2010) for the idea and circuit.
I ordered some high voltage FETs, and I am thinking of laying out a PCB using a mosfet in a capacitor multiplier and see how that works…
I am currently working on the layout of a more complicated device–the circuitry for a complete high voltage power supply which I will use to experiment with guitar amp circuits.