I have one of those cheap eBay mini tube amps that wasn't being used so I tore it apart of course.
It is powered by a 12 volt laptop type power supply. I was curious to see how they got B+ and 6.3 volt filaments for the 6J1 and 6P1 tubes. I was horrified to find that the power supply section was just tucked in there wrapped in shrink tubing that had a hole burned into it.
That power supply section is apparently a boost converter - 12 volts in and 280 volts out. The filament voltage is obtained from 12 volts through some kind of series/parallel arrangement on the circuit board. Because of its construction I can't see the board traces to confirm that.
Anyway its a super cheap way to get B+ and I'd like to know what your thoughts are on that. It certainly worked before I ripped it apart and sounded pretty good.
It is powered by a 12 volt laptop type power supply. I was curious to see how they got B+ and 6.3 volt filaments for the 6J1 and 6P1 tubes. I was horrified to find that the power supply section was just tucked in there wrapped in shrink tubing that had a hole burned into it.
That power supply section is apparently a boost converter - 12 volts in and 280 volts out. The filament voltage is obtained from 12 volts through some kind of series/parallel arrangement on the circuit board. Because of its construction I can't see the board traces to confirm that.
Anyway its a super cheap way to get B+ and I'd like to know what your thoughts are on that. It certainly worked before I ripped it apart and sounded pretty good.
I have used similar for small currents.
Downside ( that is preventable) is that they might inject high frequency
distrubancys. It's convenient as you only need +12 . To build a
conventional plate PSU you need a transformer, and few are available today,
those that are tend to be expensive.
Can you post a picture of yours ?
Downside ( that is preventable) is that they might inject high frequency
distrubancys. It's convenient as you only need +12 . To build a
conventional plate PSU you need a transformer, and few are available today,
those that are tend to be expensive.
Can you post a picture of yours ?
I've used boost converters for many builds, including my current phono and line amplifiers. Excellent performance, small size, and low cost.
The late Jim Williams on high voltage, low noise DC-DC converters:
https://www.analog.com/media/en/technical-documentation/application-notes/AN118fb.pdf
There are also some youtube videos in which he discusses the above.
https://www.analog.com/media/en/technical-documentation/application-notes/AN118fb.pdf
There are also some youtube videos in which he discusses the above.
I have two of these and they are ok for the cost.
BUT
I found they were rather noisy, noisy enough to make me think my circuit was broken!
I have also been looking at one of those. The same one is available on Amazon and probably eBay.
I would think it would have to be followed with the traditional capacitor-choke-capacitor power supply filter and that would clean it up. Or maybe not.
Here are the photos. The two leads together are 12 volts in and the single lead is 280 volts out. Looks like a very simple device with only one capacitor across the output yet the amp was dead quiet and sounded good.
Attachments
Has an interesting use listed on the advert ...
“Hunting, eradication of mice”
And charging electromagnetic guns, whatever they are.
I have invested some effort in prototype boards to evaluate a hoard of ex- tv tubes, and these look just the ticket for off heater supplies and B+ voltages.
Would you trust one for a screen supply?
“Hunting, eradication of mice”
And charging electromagnetic guns, whatever they are.
I have invested some effort in prototype boards to evaluate a hoard of ex- tv tubes, and these look just the ticket for off heater supplies and B+ voltages.
Would you trust one for a screen supply?
I've used them for screens. They work well enough.
As for odd heater voltages, there are boost converters that are suited for lower-than-B+ voltages...
An "electromagnetic" gun is just a fancy way to say rail gun.
As for odd heater voltages, there are boost converters that are suited for lower-than-B+ voltages...
An "electromagnetic" gun is just a fancy way to say rail gun.
I've used this sort: DC12V to DC 200-450V 70W High Voltage Boost Converter Step Up Power Supply Board | eBay
Seems to work, not noticed noise issues, not tried to measure the actual max output power is what's claimed though. The output voltage preset is very handy.
Seems to work, not noticed noise issues, not tried to measure the actual max output power is what's claimed though. The output voltage preset is very handy.
Good to know.
Yes I've used that boost converter a couple of times, but it tends to whistle and HATES a choke input filter (4.5H). I find the best results from non-adjustable modules.
Yes I've used that boost converter a couple of times, but it tends to whistle and HATES a choke input filter (4.5H). I find the best results from non-adjustable modules.
Looks just like this one on Aliexpress.com that I have my eye on.
DC12V to DC 200 450V 70W High Voltage Converter Boost Step Up Power Supply Breadboard-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
Looks more substantial than some of the others.
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