What are OA2 tubes and why are there more gear


using them?

I have a First Sound Presence Deluxe preamplifier which I bought used. This preamp as well as the JOULE ELECTRA use the OA2 tubes. What sort of tubes are these? When where they made and why are they not more prevalent in other preamp except in a handful of them such as the JOULE and the LAMMs, as well as the First Sound gear? What particular sound do these produce that make them appealing or unappealing for designers to incorporate them in their designs? Is there a designation that is different than the 0A2 that I am not aware off?
bemopti123

Showing 1 response by atmasphere

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.