Any Folks Here Good With Tube Regulators? 0D3 Content

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

schmidlin

Well-known member
Joined
Jul 7, 2008
Messages
165
Location
Ohio
So I'm designing this power supply for a tube amp and have a dedicated PT to supply the power tube screens and the preamp tubes.  Adding it up I should get ~110 ma at full tilt and about half that at idle.

Using 2 0D3s in series and starting with 380vdc, looking to get 300vdc regulated.

The question comes with the dropping resistor.  By my calcs, ~700 ohms is needed to pull all 110ma down to 300vdc.  Do I want to pull all of it here or should I lighten up the resistance *lean* on the regulator a bit?  Hard to find good examples of this on the web: bit of a lost art.

Thanks in advance. 
 
Hi,

The OD3 needs ignition voltage, check de data sheet. Here you can find more info: http://www.dhtrob.com/projecten/voeding_vr_tubes_1.shtml, only problem, it is in dutch, but maybe with online translation you get there, any questions/translations I will try to answer.

Data sheet link; http://www.r-type.org/pdfs/gl874.pdf

So it nees 185 minimal for 150V, so for two you need 370V.
Be aware only like 40mA max.

DJN
 
Thanks, I just realized about the current limit, looks like the screens are going unregulated.

Also found a page that says to use the tube's rating (40ma) to calculate the resistor value, and the rounded up.  Hmm...but isn't that current for the excess voltage the tube is grounding through it?  Why would current passing by it be relevant?

I found this for reference, look in the lower left:
http://www.bonavolta.ch/hobby/en/audio/6550_1.htm
 
The current SWING is relevant.

Gas tube current shall be within 5mA and 40mA at all times.

> ~110 ma at full tilt and about half that at idle.

Then the tube must absorb that 55mA swing. At full power you pick the resistor for 110mA load and 5mA tube, 115mA. Your raw supply is unregulated (or else why you regulating?), so that "115mA" is at low line voltage, better assume 20% high or 138mA after midnight. Now at idle your load is 55mA, the other 93mA flows in the gas tube.

Which may explode at over 2X rated current.

And as DJN says, you need to check your starting voltage. If the gas tube doesn't start, your poor screen and preamp get unregulated voltage.

What you usually end up with, for ROBUST regulation, is a raw supply nearly twice the voltage of your desired voltage, and current somewhat less than the 40mA max of the gas tube.

BTW: IMHO there is very very rarely a good excuse to regulate audio stage B+.
 
PRR, fantastic as usual!

Never heard "swing" in any of the manuals I never read.  I am learning the limitations of this configuration: many. 

Your explanation makes sense since the example I gave on the 2nd post uses over 2 times the final regulated voltage as starting B+. 

Don't recall using IMHO in any post here, but I like the 0D3's for their nifty light show.  Cool.

Thanks again!
 

Latest posts

Back
Top