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Powerful SMPS for tube ampifier
Powerful SMPS for tube ampifier
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Old 30th March 2019, 07:15 PM   #11
CaterpilarSK is offline CaterpilarSK  Slovakia
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Yes, I know all that whats coming for me. I read a lot of literature about this stuff and the regulations, so I have the knowledge I just dont really have "balls" to goa and experiment. First of all I aint gona be seeling this in stores, I just want it functionall and not to disturb anything arround it, if lateron there will be any demand, I may be working on a certifyable version. But I doubt any demand would even exist for a thing like this. However I do want to finally dive deep into mains powered projects. Even tho I hate to even think about powering stuff with mains, I think I do have the knowledge and its time to begin. Safety first.
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Old 31st March 2019, 12:07 PM   #12
trobbins is offline trobbins  Australia
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Did you document the design and performance of your low voltage input supply?

Are you aiming to use aspects of that for your Mains AC design?
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Old 31st March 2019, 05:45 PM   #13
CaterpilarSK is offline CaterpilarSK  Slovakia
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Yes I documented the entire design, however I found a lot of flaws and found out some interesting sideeffects. Some undesireable, some desireable.

The mains powered version will use a off the shelf chip to controll the switching, also there will be implemented opto isolation between the mains side and secondary side. Im aiming for maximum simplicity and best performance, while not surpassing component ratings.

The 10-24 version is really inefficient after the power of 20W. Getting down low as 70% and prettymuch stay the same up until 50W where the switching transformer is getting saturated to the extend of not being able to extract more power from it.

Another find was that I canot use a MOSFET with a bodydiode which is the main reason to go with an IGBT. The body diode basically snubs the reverse voltage that is pointlessly loading the transformer and diissipating the power into waste for no reason.

The low voltage version was built as a proto, giving me acess to modify anything on the go. Unlike the LV converter, the mains powered one will feature a PWM block- locking the PWM on low so the switching will stop and the converter will be simply in a standby mode. This can be used as also a "safety" switch- open chassy and such.

I dont know if that answered your question, if you have any specific questions, let me know.
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Old 2nd April 2019, 07:34 PM   #14
Shawnstium is offline Shawnstium  United States
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I have had good luck using the RECOM Isolated DC/DC Converters Rxx-B series for tube pre-amp power supplies. The units are only 5 watts, so not enough for a tube power amplifier. Most off the shelf high power/high voltage SMPS are more expensive than HV transformers.

Are you going to post a schematic?
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Old 2nd April 2019, 08:59 PM   #15
CaterpilarSK is offline CaterpilarSK  Slovakia
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Probably without values. The schematic is useless without the PCB. It was quite difficult to find the legit parts for my cad program that I do PCBs in (Eagle). In fact I ended up creating my own. So at this point its really not even an option to build it yourself except that if you would recieve the PCB from me, and even then, soldering is not a, tack it and done job, its quite the procedure especially with the pulse transformer. If and when I will complete the PSU, and it will be within specs and relatively safe, I can send you the finished product if you still are up for it. If you want the completed version of the PSU, youll only have to keep following this thread and when its going to be done, you can ask for a price or maybe even the full schematic, but making the PCB will be such a pain that nobody will even atempt it (I think).

For now, its a protype, currently only the 12V version works, and I have not made a physical functioning mains powered version yet. Ill post news about it as soon as it happens. Also there will be a video on youtube about my PSU.

So we will see.
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Old 2nd April 2019, 11:57 PM   #16
trobbins is offline trobbins  Australia
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For diyers, it is very convenient to use a commercial mains input power supply with 12VDC regulated output (especially if this is a plugpak, or module style as per a laptop power supply) as the main supply to a valve amplifier. The 12Vdc is used directly for heater powering, and as an input to and internal dc/dc converter supplying the required B+.

The dc/dc doesn't have to comply with mains ac safety standards, and only handles the B+ supply power requirement. Many options available on ebay at very low cost, such as car style inverter products that may need minimal modification. And suitable for diy designs such as your 12Vdc input supply, and others may be interested if your design shows performance benefits over what has been described in a number of threads for ebay style dc/dc options.

The ac mains supply is then (if properly chosen) compliant to all safety and base level electrical product standards for the country of use, has a quality of mass design and manufacture with performance specifications and a warranty and peace of mind.
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Old 3rd April 2019, 06:10 AM   #17
CaterpilarSK is offline CaterpilarSK  Slovakia
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You are right, but car style inverters are noisy and it really requires quite the filtering. The other problem is, generating 500V from mains is a much more efficient process than creating it from 12V. As I mentioned, 12V 50W is a really big current, and further I want to expand the power rating to 100W, which will be simply impossible to get such power from only 12V without really pushing components to the limit and generating a lot of electrical and magnetic noise.

In this case, having an aditional 12V power supply is better than powering the entire thing from the ATX PSU, because such a high current draw from the amplifier, will drag the voltage down, for the converter it doesnt matter but the tubes instead of recieving the full 12V they will recieve 11V-10V. Which does make a difference.

If youre saying, I should not even bother making this because there already exists a product but to my knowledge it does give the noise performance I desire at all. Really the point was to create the most powerfull supply with the best noise performance, and without an extreme bank of capacitance.
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Old 3rd April 2019, 08:04 AM   #18
trobbins is offline trobbins  Australia
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Quote:
Originally Posted by CaterpilarSK View Post
.. but car style inverters are noisy and it really requires quite the filtering.
What amps have you measured noise on the speaker output that originated from such a car style inverter? I'd be keen to see some spectrum measurements and details on the converter and amp.

Quote:
Originally Posted by CaterpilarSK View Post
The other problem is, generating 500V from mains is a much more efficient process than creating it from 12V.
I would suggest that a well designed, modern commercial switchmode generating a 12Vdc supply is going to attain a very high efficiency, and even more so as the output current rating increases. PFC is making sense at even lower power ratings, alleviating mains pollution considerably.

For a dc/dc step-up, generating one output is typically a much easier design set of conditions, and a 12V input dc/dc would use a regulated input voltage rail.

Quote:
Originally Posted by CaterpilarSK View Post
12V 50W is a really big current, and further I want to expand the power rating to 100W, which will be simply impossible to get such power from only 12V without really pushing components to the limit and generating a lot of electrical and magnetic noise.
I think you should experimentally measure and assess some relatively simple modern cheap inverters typically found on eBay. I have tried a few, and your comment doesn't ring true imho.

Quote:
Originally Posted by CaterpilarSK View Post
In this case, having an aditional 12V power supply is better than powering the entire thing from the ATX PSU, because such a high current draw from the amplifier, will drag the voltage down, for the converter it doesnt matter but the tubes instead of recieving the full 12V they will recieve 11V-10V. Which does make a difference.
12V at 10-15A is pretty benign in the world of power distribution, and many higher current switchmodes that require excellent end-point voltage regulation typically use a far end voltage sense circuit - fairly common and practical. Valve heaters are rated to cope with -10% voltage. So I'd suggest this is a non-issue.

Quote:
Originally Posted by CaterpilarSK View Post
If youre saying, I should not even bother making this because there already exists a product but to my knowledge it does give the noise performance I desire at all. Really the point was to create the most powerfull supply with the best noise performance, and without an extreme bank of capacitance.
Without the forum seeing your design and performance efforts so far, it's a bit difficult for commentary on whether there may be room for improvement and learning above and beyond what some cheap dc/dc can provide. Aspects such as acceptable B+ droop and then current limiting without hiccups are important, as well as thermal management of all parts and good layout parts and traces.
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Old 3rd April 2019, 12:30 PM   #19
kodabmx is offline kodabmx  Canada
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Powerful SMPS for tube ampifier
There shouldn't be any appreciable voltage drop on an ATX supply, and most are high efficiency, but the physical size requires a 4" high chassis. The nice thing about powering from 12V is portability with batteries.
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Old 3rd April 2019, 01:04 PM   #20
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by CaterpilarSK View Post
Hello, I designed a SMPS that creates 0 audiable noise in a tube ampifier. Originally this was a school project for a competition
......................
I designed the amplifier on a PCB and the powersupply too.
..............................
What I would like to know, if there is anyone even lightly interested to see a switching powersupply for a tube amplifier.
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Little about myself- Im a students I turned 17 last week and I was protiping this SMPS for about 6 months before i I got to a point of any real useable result. I made lots of amplifiers mostly transistor based or IC based AB amplifiers and Im also into analog technology. So basicaly a nerd
1) WELCOME to the Forum

2) CONGRATULATIONS on your advanced project.

Yes, there are some details to correct.
Yes, please be careful when dealing with Mains voltages, follow all safety rules

3) I WONDER why when the OP offers to share his work, politely asking if somebody might be interested in seeing it, he is suggested instead to "buy some E Bay supplies" ??????????????????

Including a 5W one ??????????????????
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