MJ sez that Schottky are kinda rare above 150V - they're also not that great, as when you get up to 200V PIV, there's not that much advantage in voltage drop using a 200V Schottky as opposed to an equivalent ultrafast diode. At voltages of 100V or below, it's a different story, especially when you dip below 60V. I work in the commercial realm, and 80% derating for PIV is considered sufficient.
why bother with Schottky with ripple voltages of 120 or 100Hz?
I did a quick search through this thread and didn't find a single match for the string "reverse", so I don't think this has been mentioned yet. If it has, I apologize.
A four-diode bridge has the advantage that no diode sees a greater reverse voltage than V_DC_OUTPUT. Not even during a mains surge. So if your transformer secondary is 30VAC loaded, 39VAC loaded, the DC output voltage is always less than 39*1.414 = 55.2 volts. None of the diodes in the bridge will ever see a reverse voltage more than 55.2 volts. It would be perfectly safe to use diodes rated for 80V in this application. There's no need to act macho and buy 600 volt diodes for this bridge. Which is helpful if you tend to prefer Schottky diodes like I do. Schottkys are plentiful below 150 volts and comparatively rare above 150V.
but, but, but rectifiers are dirt cheap nowadays, why be stingy about them?
i did a push pull 16 kt88 amp and i used 1kv, 16Amp flatpack bridge rectifier,
the amp still lives today....
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Why bother with Schottky diodes at line frequency? They have significantly lower voltage drop as compared to a std PN diode, and that lower drop can make a difference if you are stuck with a given transformer and you're trying to eke out some extra voltage.
Why bother with Schottky diodes at line frequency? They have significantly lower voltage drop as compared to a std PN diode, and that lower drop can make a difference if you are stuck with a given transformer and you're trying to eke out some extra voltage.
yes they do, but i will always use them on switching power supplies, where they rightfully belong....
Gaining maybe a lousy volt with Schotty's is trivial, and any respectable design would take into consideration any variables and not be so "touchy" about voltages.yes they do, but i will always use them on switching power supplies, where they rightfully belong....
No, it is not trivial and no they don't solely "belong" in switching PSUs.. When wanting to use a low specced transformer or if one wants as least heat as possible then Schottky diodes are a good choice. Please note that "normal" diodes can have quite a high Uf when some current flows. "Normal" diodes can be a considerable source of heat in low voltage high(er) current PSUs. Schottky diodes aren't exactly new either so why not use them? Is there an important reason not to use them?
Some are mostly used to old technology and more often than not they have too much voltage. So they drop everything everywhere with resistors turning excess voltage into useless heat in already energy wasting devices. That comes with very old and old technology, no one cared about heat and loss of energy. Good job.
Back to 2022. Energy never has been as expensive as today. Energy loss IS an item. Devices that emit a lot of heat have a hard time to be allowed on the market. Consumers see generated heat as bad as well. Many want small unobtrusive devices. Square meter heat generating audio devices are mainly for grey nerdy types. Therefor some design "low noise, low loss, low heat". Of course this mainly counts for low voltage PSUs but for some reason there is always someone mentioning 300V PSUs. Well most sources run on voltages of 12V or less. Hard to grasp for tube guys as these never work on such devices as "those are SMD". Audio players, streamers, DACs, switches, routers.... you name it. No B+ of 300V and a filament to find. Practically all have a cheap noisy SMPS so there is a chance for immediate improvement! A clean PSU.
My specialty is such PSU's and no I can not do without Schottky diodes if I want a 5V 3A PSU that is cold and built in a very small casing. Below 12V things become difficult fast when some current is needed. If you like you can calculate stuff with a 6V transformer and a 5V regulator. You will then see why Schottky diodes and LDO regulators are nice. One can use the better recent linear technology and more or less solve the classical drawbacks of those. The fact that many use SMPS means knowledge of linear PSUs is diminishing big time. Ridiculous to be a nitpicker with tube audio, use silver-oil caps and then use a transmitter to feed such devices. A choice of technological poverty, not a showcase of craftsmanship and I bet these devices aren't even measured.
If I follow the general reasoning when stupid/useless/spilling/energy wasting choices are made I can state exactly the same: just use Schottky diodes because you can.
BTW terrible thread, sorry.
Some are mostly used to old technology and more often than not they have too much voltage. So they drop everything everywhere with resistors turning excess voltage into useless heat in already energy wasting devices. That comes with very old and old technology, no one cared about heat and loss of energy. Good job.
Back to 2022. Energy never has been as expensive as today. Energy loss IS an item. Devices that emit a lot of heat have a hard time to be allowed on the market. Consumers see generated heat as bad as well. Many want small unobtrusive devices. Square meter heat generating audio devices are mainly for grey nerdy types. Therefor some design "low noise, low loss, low heat". Of course this mainly counts for low voltage PSUs but for some reason there is always someone mentioning 300V PSUs. Well most sources run on voltages of 12V or less. Hard to grasp for tube guys as these never work on such devices as "those are SMD". Audio players, streamers, DACs, switches, routers.... you name it. No B+ of 300V and a filament to find. Practically all have a cheap noisy SMPS so there is a chance for immediate improvement! A clean PSU.
My specialty is such PSU's and no I can not do without Schottky diodes if I want a 5V 3A PSU that is cold and built in a very small casing. Below 12V things become difficult fast when some current is needed. If you like you can calculate stuff with a 6V transformer and a 5V regulator. You will then see why Schottky diodes and LDO regulators are nice. One can use the better recent linear technology and more or less solve the classical drawbacks of those. The fact that many use SMPS means knowledge of linear PSUs is diminishing big time. Ridiculous to be a nitpicker with tube audio, use silver-oil caps and then use a transmitter to feed such devices. A choice of technological poverty, not a showcase of craftsmanship and I bet these devices aren't even measured.
If I follow the general reasoning when stupid/useless/spilling/energy wasting choices are made I can state exactly the same: just use Schottky diodes because you can.
BTW terrible thread, sorry.
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For consumers surely not. But if you put it on your workbench, connect measurement equipment to it, you'd surely find different performance, at least more output power with AC 😉 .Those old AA5 radios didn't care if it was AC or DC either 🙂
Best regards!
Lowest is 11.4V, highest is 11.6V. Within spec so I'm happy with it.what is the filament voltage at when the line is at its lowest? that is where i will focus my efforts at...
i once serviced a 6sn7 line amp using the Russian 6H8's running dc filaments at 5.2 volts dc, guess what, the amp sounded fabulous with such filament voltages......
No, it is not trivial and no they don't solely "belong" in switching PSUs.. When wanting to use a low specced transformer or if one wants as least heat as possible then Schottky diodes are a good choice. Please note that "normal" diodes can have quite a high Uf when some current flows. "Normal" diodes can be a considerable source of heat in low voltage high(er) current PSUs. Schottky diodes aren't exactly new either so why not use them? Is there an important reason not to use them?
Some are mostly used to old technology and more often than not they have too much voltage. So they drop everything everywhere with resistors turning excess voltage into useless heat in already energy wasting devices. That comes with very old and old technology, no one cared about heat and loss of energy. Good job.
Back to 2022. Energy never has been as expensive as today. Energy loss IS an item. Devices that emit a lot of heat have a hard time to be allowed on the market. Consumers see generated heat as bad as well. Many want small unobtrusive devices. Square meter heat generating audio devices are mainly for grey nerdy types. Therefor some design "low noise, low loss, low heat". Of course this mainly counts for low voltage PSUs but for some reason there is always someone mentioning 300V PSUs. Well most sources run on voltages of 12V or less. Hard to grasp for tube guys as these never work on such devices as "those are SMD". Audio players, streamers, DACs, switches, routers.... you name it. No B+ of 300V and a filament to find. Practically all have a cheap noisy SMPS so there is a chance for immediate improvement! A clean PSU.
My specialty is such PSU's and no I can not do without Schottky diodes if I want a 5V 3A PSU that is cold and built in a very small casing. Below 12V things become difficult fast when some current is needed. If you like you can calculate stuff with a 6V transformer and a 5V regulator. You will then see why Schottky diodes and LDO regulators are nice. One can use the better recent linear technology and more or less solve the classical drawbacks of those. The fact that many use SMPS means knowledge of linear PSUs is diminishing big time. Ridiculous to be a nitpicker with tube audio, use silver-oil caps and then use a transmitter to feed such devices. A choice of technological poverty, not a showcase of craftsmanship and I bet these devices aren't even measured.
If I follow the general reasoning when stupid/useless/spilling/energy wasting choices are made I can state exactly the same: just use Schottky diodes because you can.
BTW terrible thread, sorry.
let no one stop you, what floats your boat is where you should be.....just that there are other points of view....
i will not even call other ideas different from mine as stupid.....
for line frequencies, i will choose mass over speed...you are free to choose as you like...
rectifiers rated for 10A will have more thermal mass than one rated for 1A, and will have lower forward voltage drop...
rectifiers rated for 10A will have more thermal mass than one rated for 1A, and will have lower forward voltage drop...
It was the other way around. I think the post speaks for itself with detailed description of challenges in low voltage high current design.let no one stop you, what floats your boat is where you should be.....just that there are other points of view....
i will not even call other ideas different from mine as stupid.....
For some reason high voltage “niche in a niche” tube stuff needs to blended in where dropping several tens of Volts is normal. Diodes could have an Uf of 5V and no one would blink an eye. 1N4007 is already advanced technology in that aspect. This thread is about low voltage stuff. Many good things when using todays good Schottky diodes so no reason not to use them.
Ah the “tone”. Sorry about that 🙂
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like i said before, psu's can be designed at will....let no one tell you how you should do yours....
i guess i am lucky since i design and build my own power traffos, undervoltage is not an issue with me...
i guess i am lucky since i design and build my own power traffos, undervoltage is not an issue with me...
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The point being that I had to listen to the knowledge of more gifted people. These have taught me to be precise when it is needed, to calculate stuff and to choose parts for their specific features/purpose. Different from todays "everything goes" thinking in colors and flavors.
It also helps not to stay in ones own bubble. Please try to design that 5V 3A PSU with a 6V transformer with +/- 10% mains voltage variations, predefine maximum power to heat loss and see the challenges. That is more complicated than creating a 250 ...300V 100 mA DC B+ unregulated PSU.
It also helps not to stay in ones own bubble. Please try to design that 5V 3A PSU with a 6V transformer with +/- 10% mains voltage variations, predefine maximum power to heat loss and see the challenges. That is more complicated than creating a 250 ...300V 100 mA DC B+ unregulated PSU.
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@TonyTecson FYI: I have 11.4V with 20,000uF but on a newer build I used 90,000uF and have 12.2V - MBR6045 diode. So in my case a bridge WOULD work but you need 50$ more capacitors LOL
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