• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

RNT-900 regulator

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For this kind of money (165 EUR =~ 215 USD) I am pretty sure I can build myself a complete amplifier, together with whatever SS regulation scheme (looks like a simple capacitance multiplier times four, judging by photo and connection schematic) I might fancy that day. Granted, my PCBs are homemade, hence lower cost and less appealing look (but series made PCBs of the kind displayed in photo of the board cost 10-20 EUR apiece tops, probably even less than that).

Seriously, if this regulator doesn't give you a b***job while performing whatever task it's supposed to do you've spent 100 EUR too much on it.
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From what I can make out looking at the board and using google translate to augment my smattering of German it looks to me like in fact this is a adjustable voltage regulator which can operate with AC input voltages of up to 630Vrms or so. They mention the electrolytics are stacked for high voltage operation and have a combined rating of 900V. They talk about trying to emulate the characteristics of tube rectifiers with IXYs diodes and resistors, there is apparently a gyrator in there as well, DC output is delayed and ramps up to full value over a 30 second period. Output ripple is stated to be no greater than 1mV at any output voltage. Line regulation is stated to be mV for large variations (not specified or I missed something) in AC input voltage. I was not able to find or correctly interpret load regulation information. (I suspect based on other comments that the load regulation is comparable to a tube rectifier under varying load.) It has dissipation and current limiting built in. Two of them can be connected in series for operation to 1500V or so.. Low voltage operation allows the caps to be paralleled. The 500mA rating applies as long as the input voltage criteria are met, and the transformer can handle the current required.

This definitely doesn't sound like a capacitance multiplier to me. It is expensive but it sounds like a relatively sophisticated design. Perhaps you could get a German forum member to purchase and ship it to you. It's pretty expensive at 165 euro. ($215)
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