Hi,
To make a long story short, I'm currently in i a situation where I have plenty of tubes and output transformers to play around with but very few mains transformers (and no budget to by new ones everytime I get another idea). Many of my tubes are european sweep tubes with from the P series with 300mA heaters, which allows a bit of creativite thinking when it comes to warming them up. I also have a decent stash of medium to large mains toroids with in the 2*25-40V range and dozens of 160V 680uF Rifa electrolytics.
My latest idea is to use a 77V 5,5A (single secondary winding) 400VA toroid to produce +100Vdc @ 300mA to heat a quad of PL36 (25E5) while simultaneously producing 200Vdc @ 250mA or so for B+. The 4X8-type voltage doubler looks right for the job, but are there any hidden pitfalls to look out for when using this schematic at higher currents?
My instinct tells I would need diodes that can take a bit of flogging.
http://www.bunkerofdoom.com/lit/4x8/index.html
Another option would be to use a regular voltage doubler to produce a single 200V rail and use a quad of PL519 (40KG6), although such an amp would rely heavily on the Vkf ratings of the tubes and not go unnoticed on the electricity bill.
To make a long story short, I'm currently in i a situation where I have plenty of tubes and output transformers to play around with but very few mains transformers (and no budget to by new ones everytime I get another idea). Many of my tubes are european sweep tubes with from the P series with 300mA heaters, which allows a bit of creativite thinking when it comes to warming them up. I also have a decent stash of medium to large mains toroids with in the 2*25-40V range and dozens of 160V 680uF Rifa electrolytics.
My latest idea is to use a 77V 5,5A (single secondary winding) 400VA toroid to produce +100Vdc @ 300mA to heat a quad of PL36 (25E5) while simultaneously producing 200Vdc @ 250mA or so for B+. The 4X8-type voltage doubler looks right for the job, but are there any hidden pitfalls to look out for when using this schematic at higher currents?
My instinct tells I would need diodes that can take a bit of flogging.
http://www.bunkerofdoom.com/lit/4x8/index.html
Another option would be to use a regular voltage doubler to produce a single 200V rail and use a quad of PL519 (40KG6), although such an amp would rely heavily on the Vkf ratings of the tubes and not go unnoticed on the electricity bill.
Voltage doublers do work but their efficiency, so to say, is generally low.
The output voltage, especailly when you draw a fair amount of current, will not get all the way up to 2 times the value.
Count with at least 10% loss. They also have more ripple than a 'normal' rectifier setup.
But it will work for sure.
Be aware that the reverse voltage across the diodes will be twice than with a 'normal' rectifier, so select diodes with higher reverse voltage.
But since you have all the stuff, whip it up and measure it with a load resistance.
Jan
The output voltage, especailly when you draw a fair amount of current, will not get all the way up to 2 times the value.
Count with at least 10% loss. They also have more ripple than a 'normal' rectifier setup.
But it will work for sure.
Be aware that the reverse voltage across the diodes will be twice than with a 'normal' rectifier, so select diodes with higher reverse voltage.
But since you have all the stuff, whip it up and measure it with a load resistance.
Jan
All of my amplifier designs use 120V into a doubler / quadrupler.
You should be able to get 100V/200V from 77V including losses.
You should be able to get 100V/200V from 77V including losses.
There are many 300mA constant current power supplies in Aliexpress. I use them for P* tubes' heaters. Just make sure you get isolated ones and within the voltage range that you need.
Voltage doublers don't suffer from a lack of efficiency (stricto sensu): for example, a Latour doubler is more efficient than a full wave rectifier. Compared to a bridge, it spares one diode drop, and compared to a two-diode center tap case, it spares the under-utilization of copper.
They require larger filter caps (at a lower voltage rating though), but their power factor is the same as a full wave rectifier of the same output.
Their main drawback is the ripple frequency, equal to the mains frequency. The resulting voltage in a Latour doubler has 2*Fmains ripple, but each half works at Fmains.
Somewhere on the forum, I have made a (fair) comparison between the different options, but due to the new search function, I am not going to attempt to find it, but basically all options are mostly equivalent when compared fairly
They require larger filter caps (at a lower voltage rating though), but their power factor is the same as a full wave rectifier of the same output.
Their main drawback is the ripple frequency, equal to the mains frequency. The resulting voltage in a Latour doubler has 2*Fmains ripple, but each half works at Fmains.
Somewhere on the forum, I have made a (fair) comparison between the different options, but due to the new search function, I am not going to attempt to find it, but basically all options are mostly equivalent when compared fairly
In this post, I have tried to include all possible authors (but I probably missed some):
https://www.diyaudio.com/community/...here-is-the-legacy-thread.387391/post-7054386
If you have other names to attribute to the topologies, they would be welcome: things get reinvented all the time by many people: if you read an USSR vulgarization paper, everything came from Russian inventors: Popov, Tsiolkovsky, etc. The same with British, French, Italians, etc.
Let's try to be complete and exhaustive....
https://www.diyaudio.com/community/...here-is-the-legacy-thread.387391/post-7054386
If you have other names to attribute to the topologies, they would be welcome: things get reinvented all the time by many people: if you read an USSR vulgarization paper, everything came from Russian inventors: Popov, Tsiolkovsky, etc. The same with British, French, Italians, etc.
Let's try to be complete and exhaustive....
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