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alexmoose 19th December 2006 09:37 PM

Using Gas Regulators
 
Hi everybody!

I am trying to learn something new about yet another interesting tube technology. I want to learn how to use gas tubes to regulate the B+ on a phono supply.

I would like to ask everybody if they know the basic rules. I know practically nothing about them! I guess the basis questions are

1. how do I set the current on them?

2. what is the largest cap I can put next to them?

3. if I need twice the voltage tolerance, can I just put two in series?

Thanks so much,

Moose

Sherman 19th December 2006 09:55 PM

Alex,

Have you checked these?

http://www.mif.pg.gda.pl/homepages/f...41/g/GL874.pdf

and

http://www.mif.pg.gda.pl/homepages/f.../137/0/0B3.pdf

EZ_Angus 19th December 2006 09:56 PM

Re: Using Gas Regulators
 
2. what is the largest cap I can put next to them?

.05 uf or so I'd say


3. if I need twice the voltage tolerance, can I just put two in series?

yep


EZ

Sheldon 19th December 2006 09:57 PM

Re: Using Gas Regulators
 
Quote:

Originally posted by alexmoose
1. how do I set the current on them?

Two basic methods:

Use a resistor in series prior to the reg. tube to limit the current. Size the resistor so that the voltage at the output of the resistor equals the regulator voltage at the operating current of the system (current draw of the preamp, plus about half the max. continuous current max. for the reg. tube).

Or precede the regulator tube with a current regulator set to deliver the operating current of the system as defined above.

Note that the tubes can tolerate about twice the continuous maximum current for a brief start up period - to allow your preamp tube filaments warm up.

Quote:

Originally posted by alexmoose
2. what is the largest cap I can put next to them?
Generally 0.1uf. Can use a larger cap with series resistance.

Quote:

Originally posted by alexmoose
3. if I need twice the voltage tolerance, can I just put two in series?

Yes, though you are not restricted to two of the same type. You can combine different tubesin series get the voltage you want. Or use more than two also.

Sheldon

SvErD 19th December 2006 10:18 PM

http://www.diyaudio.com/forums/showt...471&highlight=

Tom Bavis 20th December 2006 02:40 AM

Thanks to Bas Hornemann for the scans...

http://www.audiophool.cjb.net/Misc/sylvr1.jpg
http://www.audiophool.cjb.net/Misc/sylvr2.jpg

kevinkr 20th December 2006 02:43 AM

Generally anything much over 0.01uF (10nF) is inviting trouble - I have actually had OA2 and OB2 oscillate with 0.1uF caps across them.

You can combine different types in series from the same general family OA2, OB2, OC2 to get the voltages you need. Note that the OC2 is rather unpredictable voltage wise (68 - 88V IIRC) whereas the OA2 generally regulates around 150V.

I found them unacceptable in a line stage due to excessive noise, and I think you might run into the same problem with your phono stage.

Using them with larger caps and isolating resistors may result in a relaxation oscillator if component values aren't chosen quite carefully.

I'd look for an old ARRL manual from the tube era, ham gear used a plethora of gas regulators and there are some good tips to using them.

Eli Duttman 20th December 2006 04:10 AM

Kevin hit the nail on the head. If a 100 nF. snubber doesn't oscillate you're lucky. OTOH, 47 nF. should not oscillate and do a decent job of quieting things down.

A stack using either VR150/VR105 (Octal) or 0A2/0B2 (7 pin mini) should be near perfect for many phono circuits, including the "Old Warhorse" RCA.

GK 21st December 2006 06:48 AM

You also have to take note of the tubes firing voltage and make sure that the voltage supply for the tubes current limiting resistor exceeds it by as reasonable safety margin.
It varies from tube type to tube type, but the firing voltage can be quite a lot higher than the stabilisation voltage.


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