Tubes Asylum

RE: Mystery 12AU7 = RFT

65.78.8.172

In Reply to: RE: Mystery 12AU7 = RFT posted by Thermionic27609 on June 30, 2009 at 20:33:08

Nice tube. It's the OE tube Conrad-Johnson fit in their PV-12/L/A/AL preamp, a preamp which I happen to own and enjoy. I'm not sure what these codes mean either. I've seen some of the Eastern European sellers making manufacturing date claims for these tubes indigenous to their part of the world, which kinda appears that they seem to have some insight into decoding these codes. Though maybe they're just makin' it up ;)
Early 1950s would be WAY too early for these. I surmise from my own sleuthing and ownership of several varieties of RFT ECC82s that this tube with the single heavy-duty getter support and small halo getter is the final version of this RFT tube. It dates to the 1970s, and could have been produced into the 1980s.
Yeah, RFT ECC82s and ECC83s all have these small, 12AT7-like plates. Some Tungsrams have plates like this, too, but there're enough differences to distinguish all from one another (including the Tungsram "tag"). Identification of whether an RFT is an ECC82 or an ECC83 could be a little more work in the absence of their delicate silkscreened type markings.
So, double, maybe even triple, branding - HP, Amperex, and RFT? Interesting and curious. Maybe these particular tubes were supplied by Richardson to HP as Amperex-branded. I've got some ECC82 10Ms that're RFTs. Gotta be Richardson?
It's very handy to be able to make a positive tube ID, but it can be plenty convoluted, even for folks more familiar with these things. Raytheon-branded Japanese-made tubes that still wear the Raytheon EIA code (which makes sense as Raytheon is the final supplier in the chain?). Amperex Bugle Boy "Made in Holland" silkscreened tubes that have Valvo Philips codes (which has to trump the silkscreening, right?). And on, and on. Fun, right?
I really like all the RFT ECC82s and ECC83s I've used. Both have typically sounded on the "neutral" side of things in most of the systems I've used them in. Clean, clear, extended, and tidy. (did I just write "tidy"? ;) )
- SJ

Edits: 07/03/09 07/04/09

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