Alternative filament supply for 01A line stage

[arnoldc]

Hi,

This is my simple 01A line stage. Currently using the solid state power supply as seen in the schematic. The 01A filaments are getting supply from two unregulated 5V DC wall warts which causes hum, quite loud.

Since I like the sound, I'm planning to use the alternative PSU at the bottom of the drawing.

Do you think the filament supply is enough? I've seen some laced with lots of capacitance and common mode chokes.

Is it better to use a voltage regulation or current regulation for a DHT tube?

Thanks again.

 

[Eusebius]

It is definitely better to use current regulation - sounds better. A good design is the RonanReg, but I don't quite know where to find the schematic online. It has two voltage regs and the third and last stage configured as a current reg.

You can get a reasonably good result by using a common mode choke at the end of two voltage regs (better than voltage regs alone), but the current source sounds cleaner. There is no benefit in putting a CMC at the end of a current source, in fact it sounds worse for some reason.

 

[kevinkr]

Hi Arnoldc,
Definitely go with the current regulation, with adequate passive filtration ahead of the current regulator you won't need additional voltage regulation. I use a very similar circuit to what you have drawn in a lot of my dht projects including a line stage and it works well.

 

[arnoldc]

hi Eusebius, so you suggest two stage voltage regulator topped off by a current regulator?

hi kevin, is the one drawn on my schematic sufficient enough?

thanks guys.

here's the prototype by thw way...

An externally hosted image should be here but it was not working when we last tested it.