DC heater scematic recommendatoins

[Jonas]

Does anyone have a DC heater circuit recommendation?

[glass54]

Hi Jonas,
For clarity and your needs, how many tubes (I'm assuming preamp tubes only) or just first tube on input?
It matters 
Regards,
Mirek

[acheld]

Does anyone have a DC heater circuit recommendation?

Scroll to the bottom section and read . . .  http://www.valvewizard.co.uk/heater.html

[mresistor]

Does anyone have a DC heater circuit recommendation?

Scroll to the bottom section and read . . .  http://www.valvewizard.co.uk/heater.html

The way Merlin shows the filament lead dress is interesting and may be helpful to me in a recent build. Thanks for the link.

[Jonas]

thanks Mirek, and good question.  I have always considered the PI to be part of the power amp so would it be best practice to keep this tube on AC?

Thanks for the link - is it best to keep DC heaters limited to V1 only?  I see the diagram shows only one tube and I'm reading the notes regarding the amount of filtering required and the extra current demands (600mA).

Maybe the better question is when would you want to use DC heaters?

Thanks again!!

[acheld]

Maybe the better question is when would you want to use DC heaters?

Merlin's paragraph says it all for me. 

For whatever reason, heater induced hum has not been an issue in my builds, so I have not resorted to the bother of DC heaters.   

   I have other demons to slay -- namely unwanted high frequency oscillations . . .

[HotBluePlates]

... Maybe the better question is when would you want to use DC heaters? ...

Very high gain preamps, or when you have frequent problems with heater-to-cathode leakage in preamp tubes.

[Jonas]

thanks, I'm not considering a very high gain preamp so I think I will stick with AC heaters.

[glass54]

To add to HBP's advice, It's very useful to have DC heaters for Phono Preamps (RIAA), Mic Preamps and possibly Tube-based test equipment.
I have attached a simple 3 Terminal regulated Heater supply schematic that I have used successfully before.
Regards
Mirek

[acheld]

It's very useful to have DC heaters for Phono Preamps (RIAA), Mic Preamps

Interesting.   I've been looking for a schematic for a Phono preamp with line level out.

HiFi is a different skill set than guitar amps . .  .

[glass54]

Off Topic Acheld but here is a link to a good project and in Polish to extend you  http://skarabo.net/sid-21-prea-riaa.htm
If you want to PM me, for more ideas, you are welcome.
Regards
Mirek

[tubeswell]

I have always considered the PI to be part of the power amp…

Well, in terms of its signal inverting function, it’s necessary for a push-pull ‘power amp’ (if you’re not using an interstage transformer to invert the signal).


But electrically, in most pp amps, it’s a preamp tube (so it’s power supply current demand is relatively small), and it takes its power supply from a separate part of the power supply circuit (compared to the power amp). So if you’re grounding the PI returns with the power amp returns, you ‘could’ be making the amp hummier than it needs to be (or not).