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6J1 Tube Preamplifier u$s35.
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Old 22nd April 2019, 08:07 AM   #11
t-minik is offline t-minik  France
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ICG, did you find Tube-03 on Ali?

That one claims it boosts dc to 150v, but capacitors seem to be low v rated.
TIANCOOLKEI Tube Amplifiers Audio Board Amplificador DIY Kits Fever Bile Pre amplifier Hifi 6J1 tube headphones amplifier-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
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Old 22nd April 2019, 01:57 PM   #12
ICG is offline ICG  Germany
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The page doesn't work for me, it says article not found. Maybe they don't want it to show in Germany?

As for the capacitors, there are several possibilities. The most logical would be to create the 150V with a cascade/voltage doubler or more in series. The capacitors are in series and therefore lower the capacity/current but increase the voltage rating and the effective voltage. The cascade needs a bunch of diodes and capacitors and AC voltage.

Another possible expaination would be they use film capacitors for the anode voltage, which have usually a much higher voltage rating and the electrolyte caps are. I can't tell though because I can't see the article.

They could also have a buck converter on the board and the low rating capacitors are just there to buffer the input or the voltages for the control ICs. because of high frequency of the converter a small film capacitor might be enough.

To make fake claims is ofcourse still a possibility though. That happens a lot on chinese sellers unfortunately. They usually don't just straight out lie but increase the numbers in the specification slightly.
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Old 22nd April 2019, 02:11 PM   #13
avtech23 is offline avtech23  Australia
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6J1 Tube Preamplifier u$s35.
Does this link work for you? Worked for me: TIANCOOLKEI Tube Amplifiers Audio Board Amplificador DIY Kits Fever Bile Pre amplifier Hifi 6J1 tube headphones amplifier-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
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Old 22nd April 2019, 02:18 PM   #14
ICG is offline ICG  Germany
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No, it says the page/article cannot be found. I don't expect the link to be wrong, it's much more likely they don't want the page to be displayed in some countries/areas.
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Old 22nd April 2019, 04:34 PM   #15
t-minik is offline t-minik  France
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Strange thing both links re working for me...
That Tiancoolki board is red with a vertical dc-dc converter and 100v rated Grey caps... Not very confident in...

In tube-03 Dc-dc is made with a uc3843a close to 75khz, exaxt schematics as that one except I don't get smd cap values :
https://danyk.cz/noteb_en.html

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