What are OA2 tubes and why are there more gear

UHHHH!!!! I had one 0A2-tube break, and both channels continued to work however it did not sound as good as usual.
I wondered why I started to lose my hair!

The cool glow on O** series tubes is from the gas fill - argon, neon, xenon, etc. Not from any radioactive elements. Though some larger (high voltage transmitting type) tubes do give off Xrays in minor amounts.

-Ed

Hm. Well I have 5 of these. I'm selling off much of my collection, anybody interested?

They are RCA and pulled in about 92 from research lab gear being thrown out. Probably very little use. Will test on my TV7 later.

Jim

OA2s work much the same as Zener diodes but have a set of issues that I would think would make the Zener a preferred design means. One of them is that the tube makes noise when it fires (which is continuously) so you have to bypass them and isolate them from the regulator that is using it as a voltage reference.

Zeners make noise too but they are less problematic, plus you can choose zeners to make a variety of voltages. None of these issues present much challenge to a competent designer- consequently their use would be primarily for show (although they are functional) than anything else.

Contrary to reported above, different samples of gas regulator tubes do sound different, so it makes sense to try a variety. Fortunately, you can buy these off the internet at quite low prices since there is relatively low demand. In my experience, using the larger OA3, OB3, OC3 and OD3, different brands all sound different and older versions of the same brand usually sound better. The good news is that when used properly gas tubes have a virtually unlimited lifetime.