• 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.

PSU transformer-tappings

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Well, just a quick 'yes / no' question... could'tn find anything on a 'search'....

If having a transformer like on the picture, can both the 350V and the 300V windings be used at the same time? F.ex. one winding to the driver and one to the Output stage in a power amp?

Let's say the 350V winding can handle 200mA. Is it best to draw the most current from the largest winding?



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Hi Stigla

That seamed like a simple question when you asked it, didn't it.

With out getting into a lot of details "yes" you can use all of the taps on the secondary to supply different power supply voltages. The total current for all voltages should not be greater that the maximum current rating for the highest voltage winding.

Thats not to say that the maximum total current couldn't go a little higher than the 200ma you spoke of but for a safty factor I would not push it. The V/A rating of the transformer should be your guide here.

Have fun

this trannie is meant to feed a dual vacuum tube rectifier. As the voltage drop is considerably higher than with SS recitfier, most of these trannies have two different pairs of taps, just to get the valtage about right.
Unless a Graetz bridge, the dual rectifier needs two times the voltage, one for each rectifier, to achieve the desired output voltage.

However, unless your driver is as juicy as your output tube, you should be able to use 300V for driver and 350V for output. Or inverse, makes sense in some configurations. But you still have no galvanic separation.

I am a but paranoid concerning interstage crosstalk; this alone would be the reason for me to have a separate supply (including an own mains trannie) for the driver and possibly for the input stage. I see no real benefit to derive the driver supply voltage from the secondary's "autotransformer tap".
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