VR tubes, minimum current

tomchr · 22nd February 2011, 07:38 AM

Folks,

I'm toying with the idea of using a voltage regulator tube as the reference voltage in a voltage regulator. Specifically, I'm thinking to use a 0A3. I like the looks of it....

The maximum current of the 0A3 is about 30~40 mA if I recall correctly. But is there a minimum current that's needed to ensure stable operation?

~Tom

aardvarkash10 · 22nd February 2011, 07:43 AM

yes, and a minimum voltage difference too for both operating and striking (start-up). On the spec sheet usually.

mastodon · 22nd February 2011, 08:13 AM

Minimum current for regulation is 5mA for the 0A3, as per the Tung Sol datasheet.

DF96 · 22nd February 2011, 11:21 AM

Did you choose the 0A3 for its appearance or performance? Is this art or engineering?

Lingwendil · 22nd February 2011, 04:46 PM

Quote:

Originally Posted by DF96

Did you choose the 0A3 for its appearance or performance? Is this art or engineering?

I personally use them for both, they're a nice big zener that looks great, is more rugged, equivalent noise specs (often better IME )and cost is usually about the same when purchased as surplus.

Back on the OP's question, run 'em at around 10 ~ 15 mA and you're set. For even better performance use a CCS.

bob91343 · 22nd February 2011, 05:29 PM

A zener diode will not do as well; it will have a temperature coefficient that may bother you. VR tubes are very good in this respect.

Wavebourn · 22nd February 2011, 05:34 PM

Temperature effect of Zeners when used to power tube stages, even directly copuplet, does not bother me at all. But tubes look better.

tomchr · 22nd February 2011, 05:46 PM

Quote:

Originally Posted by DF96

Did you choose the 0A3 for its appearance or performance? Is this art or engineering?

Yes!

I love the orange glow. It's purrrdy...

10~15 mA. Oof! I'm coming down from 600+ V. That's a lot of power in the series resistor.

~Tom

Wavebourn · 22nd February 2011, 05:56 PM

5 mA is enough.

zigzagflux · 22nd February 2011, 06:54 PM

Especially if you supply it with an ultra-simple CCS, maybe with the 900V rated IXYS device (no need for cascoding), the high voltage isn't really a problem. Firing is all but guaranteed even with 5 mA when you use a CCS.

22nd February 2011, 07:38 AM	#1
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	VR tubes, minimum current Folks, I'm toying with the idea of using a voltage regulator tube as the reference voltage in a voltage regulator. Specifically, I'm thinking to use a 0A3. I like the looks of it.... The maximum current of the 0A3 is about 30~40 mA if I recall correctly. But is there a minimum current that's needed to ensure stable operation? ~Tom

22nd February 2011, 07:43 AM	#2
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	yes, and a minimum voltage difference too for both operating and striking (start-up). On the spec sheet usually. __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

22nd February 2011, 05:34 PM	#7
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	Temperature effect of Zeners when used to power tube stages, even directly copuplet, does not bother me at all. But tubes look better. __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

22nd February 2011, 05:56 PM	#9
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	5 mA is enough. __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

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22nd February 2011, 08:13 AM	#3
mastodon diyAudio Member Join Date: Jan 2011	Minimum current for regulation is 5mA for the 0A3, as per the Tung Sol datasheet.

22nd February 2011, 11:21 AM	#4
DF96 diyAudio Member Join Date: May 2007	Did you choose the 0A3 for its appearance or performance? Is this art or engineering?

22nd February 2011, 05:29 PM	#6
bob91343 diyAudio Member Join Date: Mar 2010	A zener diode will not do as well; it will have a temperature coefficient that may bother you. VR tubes are very good in this respect.

22nd February 2011, 06:54 PM	#10
zigzagflux diyAudio Member Join Date: Oct 2006	Especially if you supply it with an ultra-simple CCS, maybe with the 900V rated IXYS device (no need for cascoding), the high voltage isn't really a problem. Firing is all but guaranteed even with 5 mA when you use a CCS.

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