I had a PCB custom made for my capacitor multiplier–as they said in Flashdance, What a Feeling!

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…

This is the device itself, very small–around 2×3 inches. Looking at it, I can see that I could have packed the parts more densely for a smaller device. I hope it will fit in the Hiwatt. I noticed the ones I built by had were smaller. For instance, the resistors and diodes were vertically mounted and the caps were closer together. I could also put the silkscreen message with my name on the other side.
Maybe due to the low load, but the output is surprisingly smoother than the input. The idea of this device is to use a transistor in a circuit which simulates an extremely large filter capacitor–roughly speaking. I see some sort of high frequency noise on that sawtooth waveform, not sure where it is coming from. Note that I had to use a 50 times higher range to show any ripple at all in the output signal. I believe under full load, the output ripple will be maybe 1/10 of the input sawtooth wave.
Here is the test setup. The meter on the far left is measuring the dc voltage coming out of it, 502 volts. The meter on the far right is measuring the current through it, 1.1ma. And the scope on the top is measuring the waveform going in and coming out of it. Smoother is better. The device itself is buried under a bunch of wires in the center of the workbench. There is also a bunch of junk on the workbench not related to this activity.

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.

There is the schematic of the device as I entered it into the KiCad design tool. The high voltage made it simpler to put two capacitors in series. The resistors by the caps are to ensure equal distribution of voltage among the two despite the inevitable differing leakage currents in the caps. The diodes are there to protect the transistor from power on and power off voltage transients. Other than that, it’s an extremely simple circuit but it does the job surprisingly well.

This is what it looked like in the KiCad PCB layout tool.

More tales of Mark and Steve Gursky

I knew Steve and a bunch of other guys from hanging around in an internet forum for recording studio engineers. I went there on the rumor that someone had some stems from Zeppelin’s Whole Lotta Love. Never did not get them, but I started reading a series of posts called the Bitch Slap Diaries containing a hilarious compendium of recording studio shenanigans. At times it had me laughing so hard I had tears running down my face. I have always been drawn into the world of how things work, since I am better with electronics and engineering than I am with music. I had read recording magazines voraciously, and later the internet provided even more information. So, I had a lot of book knowledge when we talked about recording and mixing, and they graciously allowed me to hang out and pretend I was one of the guys instead of a wanna-be with a boring day job…

At that time, the forum attracted some very successful and humorous music industry types and we had a lot of fun. I recall one forum regular who had been on a team that received a Grammy for a song he helped record. He was so modest that he claimed his sole contribution to the project was sitting at the keyboard of the computer running pro tools and hitting the space bar to start and stop the recording… Even his modesty was humorous.

Steve’s web handle in the forum was Loudist, and he sure loved to stir the pot–shit slinging as it was known, and I certainly enjoyed slinging plenty of my own. Some decades have passed, and I can’t even remember my own original internet handle from that forum. One day somebody blew my mind when he told me he was posting under more than one alias. Well, it didn’t take long before I created a bunch of my own and at times engaging in flame wars with each other or me, and at other times praising me effusively. Those in the know were suitably humored.

There was one forum member who was kind of aggressive and obnoxious, at least as I saw it. I created an alias using his alias but I put a period in front of it so the software allowed me to create it as being different from his existing one. I used the same avatar photo. I created posts where he seemingly apologized for his erroneous ideas and posts and praised me. Most people could not tell the difference with the period at the front of the alias, and much confusion ensued.

After a while it got so that people could immediately recognize my writing style and would ‘dox’ me after a couple of posts. We had a lot of fun until at some point everybody moved to other forums and like many good things, it came to an end.

It was in the middle of this that I started developing a relationship with Loudist on the forum, as I did not know his real name for a while. He ultimately invited me to a kind of secret forum where a group of the regulars would socialize and to some extent plan concerted shit stirring in the forum. Here I got to know him better and we began speaking on the phone.

Loudist had a dry and dark sense of humor, and a love for music, and we got on famously. He did have the habit of talking for hours on the phone. When he called, that was the end of anything else I had planned for the evening. We spent countless enjoyable hours discussing the Theory of the Popular Song, and solved many other world problems as well… 😉

On one occasion, I was flying to Colombia and had a 6 hour layover in Miami. I made plans with Steve for him to pick me up at the airport and we would go out to lunch. Thusly, I met him in person. Steve took me on a tour of a recording studio he did some work for. I learned that gold records are simply regular records with gold paint. And the records are not of the actual album, but rather a record of some unsold stock that had the same number of tracks. The actual record itself was worth money to sell, so they would not waste that on a wall decoration…

On November 21, 2005, to my horror I saw a post on the forum entitled “Loudest has died”. I resolved to fly to Florida and meet his family and extend my regrets–and did so. Some other guys from the forum came as well, and we car-pooled to the funeral reception. On the way, these guys started blowing doobie in the car. I did not participate, but got plenty of second had smoke… When we showed up at the house and opened the car doors, some smoke billowed out, and I felt like it was a scene from the movie Up In Smoke. My clothes smelled like reefer and I wanted to tell Steve’s relatives that I wasn’t inhaling, but that would have made it more awkward, and nobody really cared.

At this gathering, I had the chance to speak to one of the engineers who recorded the Layla album, and he gave me the skinny on how that went down–but that’s a story for another day. Also met the guy who mixed down La Vida Loca and heard some back story on that as well. I joined a dinner in the hotel with these industry guys around the table, dishing the gossip on the rich and famous, and that was as cool a thing as I could ever imagine.

Steve’s brother played Pink Floyd’s Wish You Were Here on an acoustic guitar and sang it, and he remarked it was the hardest song he had ever played. Loudist, I remember and miss you, and with all my heart, wish you were still here.