Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Bieworm on June 13, 2022, 02:36:03 am

Title: PT wiring question / confirmation
Post by: Bieworm on June 13, 2022, 02:36:03 am

Hi guys!

There is something in need to get confirmed. Am I correct to assume that when I use the secondary HT winding like in the drawing that I should end up with a 'kind of' half power switching? I mean, I could use the winding like that, no?

Thanks in advance...

Title: Re: PT wiring question / confirmation
Post by: sluckey on June 13, 2022, 05:29:18 am

The idea is sound but your voltages are wrong. You really have 0v-300v-600v which will give you about 848v or 424v into a cap input filter.

The Twin (https://el34world.com/charts/Schematics/files/Fender/Fender_the_twin.pdf) amp does something similar but with lower voltages. Notice that only the output tubes plates and screens are changed while the rest of the amp uses the "high power" voltages. Oh yeah, you must also switch the bias voltage.

IMO The Twin method is more realistic than your idea.

Title: Re: PT wiring question / confirmation
Post by: Bieworm on June 13, 2022, 06:13:17 am

Thanks Steve!

I'd be better off with this one then?

https://www.tube-town.net/ttstore/toroidal-185va-power.html

Title: Re: PT wiring question / confirmation
Post by: sluckey on June 13, 2022, 06:39:14 am

That gives more practical voltages. If you plan to implement this idea into a real amp then I urge you to study the twin method and copy that instead of simply switching the AC voltage per your drawing.