5ar4 filament voltage

[Nikon1975]

Dear All,

I am building a simple HV power supply to test various amp circuits. It will be used with a variac to variate the output voltage.
My question is: if I use a tube rectifier like the 5ar4, how sensitive is this tube to the supply voltage of the filament?
If I source the filament voltage from the same transformer connected to the variac, changing the supply voltage will also change the filament supply. I have I second transformer I could use to keep the 5V supply voltage constant.

Regards,

Davide

 

[rayma]

Definitely go separate transformer.

 

[nigelwright7557]

The 5V heater supply must be floating so must come from its own winding or transformer.

 

[woodo]

The Valve Wizard

Valvewizard implies at least for signal tubes +|- 10% for filament voltage even tighter. Doesn’t explicitly mention rectifier tubes variation though reasonable to assume similar recommendations.

 

[audiowize]

This is a great application for a solid state rectifier.

 

[kodabmx]

Right? What's a pair of UF5408 cost? Like 5 cents?

 

[petertub]

Dear All,

I am building a simple HV power supply to test various amp circuits. It will be used with a variac to variate the output voltage.
My question is: if I use a tube rectifier like the 5ar4, how sensitive is this tube to the supply voltage of the filament?
If I source the filament voltage from the same transformer connected to the variac, changing the supply voltage will also change the filament supply. I have I second transformer I could use to keep the 5V supply voltage constant.

Regards,

Davide

This is an excellent place to use Si diodes, 1N4007 is recommended.

 

[Eli Duttman]

Peter, with all respect, 1N4007s should not be allowed within a Light Year of any HIFI PSU. They are very noisy. The drop in replacement UF4007 generates much less switching noise and is easily snubbed into near silence.

 

[petertub]

Peter, with all respect, 1N4007s should not be allowed within a Light Year of any HIFI PSU. They are very noisy. The drop in replacement UF4007 generates much less switching noise and is easily snubbed into near silence.

I know. But this was a test ps , an experimental work.

But yes, no problem with uf4007 it's a matter of supply

 

[Nikon1975]

I plan to have the diode option, but one of the goal to have the psu is to test the system to find the exact value of the ac I need for the final design, taking into consideration the loss in the rectifier.

Thanks,

Davide

 

[kodabmx]

That's what the datasheet is for 🙂

 

[Eli Duttman]

I plan to have the diode option, but one of the goal to have the psu is to test the system to find the exact value of the ac I need for the final design, taking into consideration the loss in the rectifier.

Thanks,

Davide

Run the 5AR4/GZ34 with a dedicated 5 VAC energizing its heater. The GE datasheet indicates +/- 10% as being acceptable. FWIW, I prefer +5%/-10% as a longevity measure.