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OLDER DECWARE GEAR SUPPORT >> TORII MK III >> OA3 replacement?
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Message started by Hipfan on 09/04/12 at 01:45:43

Title: OA3 replacement?
Post by Hipfan on 09/04/12 at 01:45:43

I was losing power in my left channel and noticed that the left channel OA3 regulator tube was flickering, so I shut the amp down. Upon re-power up, it seems OK. Not sure if it is bad or not. If so, what is a recommended replacement? The stock tube in the Sylvania OA3.

Title: Re: OA3 replacement?
Post by Lon on 09/04/12 at 04:12:24

I've had good luck with RCA OA3, so I would recommend trying one of those.

Title: Re: OA3 replacement?
Post by will on 09/04/12 at 04:43:47

I have tried a number of OA3s and like them all for different sound, some brighter and more open, some warmer, some punchier, some more or less balanced, but my fav now is a short straight sided bottle labeled Ameperex. The 50s RCA ST coke bottle shape that came with my amp is a least favorite for me, but a perfectly good sounding tube.

Tubeworld usually has a good selection if you can't find what you want on Ebay or wherever. Some OB3s are really good too, especially Raytheon or Tungsol.

Have you checked the tube pin connections... cleaned the pins and slid the tube in and out of the socket a bit with deoxit on the pins?

Title: Re: OA3 replacement?
Post by Hipfan on 03/11/13 at 22:28:30

Regarding the Sylvania OA3. I noticed there are a few variations of these tubes. I've seen the coke bottle type in 3 different sizes and also a non-bottle tubular version. Do these all sound the similar?

Title: Re: OA3 replacement?
Post by will on 03/12/13 at 01:58:37

I am not sure. The only Sylvania OA3 I have is early 80s, ST (coke bottle) shape and they have a really good, complete sound that is quite open and transparent. The 50s STs I have are warmish. Also the OB3 ST and OC3Ws I have from the fifties are warmish...the Raytheon/Tungsols are nice tubes and warm, and the Sylvania OB3 ST I have are a little less warm, but still on the warm side.

A Russian tall/straight bottle I have is very open....tending to hard/edgy unless balanced with pretty warm tubes. I have some sylvania short straight OC3s (70s) that are quite open and sound good. Some Raytheon, RCA and Amperex, short/straight, all warmish and probably earlier vintage.

So go figure! I wonder if the early stuff is more warm and the later...more open...no solid information here though.