Yup, tube amps really are different from their younger cousins!

EL34world.com is a great place to learn about this stuff.? Well informed folks over there.? Also, is reputable.?

chris

On Fri, Jan 3, 2025 at 12:18?PM orders2010 via <orders2010=[email protected]> wrote:

thanks for the additional information.

I found the datasheet for the transformer, and collected the DCR values and needed voltages.

I adjusted the PSUD2 app values as you suggested, and I removed the zener (compensation) from the formula. Full PT voltage is 325V.

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Still does not make much sense to me! The numbers just do not add up the way I would expect them to. My VC1 should be a lot higher than 306Vdc.

For grins and giggles I pulled a schematic from a popular fender 5E3 design site, along with data 9and design tips) from The Valve Wizard, and input these values into PSUD2. Even with this new information, the program did not generate the numbers even close to the actual values that were on this sample schematic I pulled!

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Is VT1 RMS voltage of 287.6 the rectified voltage?? that just seems real low. I think I was measuring way over 350V on my bench test bed.

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So at this point, I think I will just leave it as it is, and finish building the rest of the amp circuit, and then hook up this supply and carefully bring up the mains and measure what I get. Adjust as needed to bring it into spec. I think this Hammond PT, is only around 70mA. I think I would need closer to 125mA, but you would think you could control the amount of current being drawn, by lower plate voltage and biasing the amp cooler! But perhaps I don't understand it. I'm a solid state engineer.... tubes were before my time!

What I do not yet understand about tube amps is how the current changes as you increase signal, and how the OT impedance affects the current load. So I am concerned that this little PT will be way under spec, causing it to get real hot, or even blowing it out. But I will try it anyway, since it cost me zero $. If needed, I will buy a new appropriate speced PT.

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Side note for PSU2 design revision suggestions... It would be convenient to show the wattage at each of the nodes. the other suggestion is on the colors of the graph lines. They change each time you run the simulation! It would be nice to make these static with color choices of your own. And I would eliminate YELLOW all together. Its too hard to see!

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Thanks.

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