Single Ended Hum

[Helmholtz]

It is rather useless trying to adjust B+ without load.
Just consider the voltage drop across the 18k resistor with a 50mA load. Even a 1k series resistor will drop 50V.

If you want to predict loaded B+ you need something like PSUD2 or lots of experience in power supply design.

[leadfootdriver]

Seems easy to do without a program.

[Chuck H]

Seems easy to do without a program.

Things aren't always as they seem.

[Helmholtz]

Seems easy to do without a program.

Oh well.

Look at your nonsense "design" of post #76.

Connect the amp and see yourself.

[Chuck H]

You basically just dismissed what Helmholtz offered in an effort to help you. I don't think you understand how cavalier and rude that was. Surely you don't think his advice is in error? The only way to arrive there would be a result of your inexperience and desire to have things be as you perceive them whether it's real or not.

P.S. If you DO connect the amp to that transformer with an 18k resistor following the rectifier, make sure the resistor is rated over fifteen watts and don't expect anything to work.

[Helmholtz]

Thanks nosaj!

[Chuck H]

Hey leadfootdriver, The reason adjusting voltage without a load on the transformer doesn't work is because the transformer, as a circuit itself, has resistance. The more current you draw through a resistance the more the voltage will drop. So the same would apply for your 18k resistor. You chose that value based strictly on unloaded voltage division. This works fine for most preamp circuits, the bias supply, filament elevation, etc. because these circuits don't draw significant current. As it happens a value of 18k with the tube circuits attempting to draw their needed current after would basically crash the power supply to almost nothing and likely create a lot of ripple. A simple series resistor, of a much lower value and with no consideration of voltage division, would probably be sufficient. But you'll need to have your circuit running to measure and adjust the value. Probably something like 150R-220R rated for 10W. Or... You could do like Helmholtz suggested. Download Duncan PSUD2 and learn to use it. It's been a recommended and useful tool for many here.

[loudthud]

There's a version of PSUDesignerII that runs online for those not running a Windows OS.