Originally Posted by gibosi
I have seen Mitcham E188CC (VR1-R0A1, but with dimpled getters, these are 1970, rather than 1960), and RTC printed on the tube. I wonder if there are Blackburn E188CC?
Hmm, yeah most Mullard-made E188CC and E88CC variations I see seem to be from later times; for example I keep on bumping into RTC branded E188CC but made by Mullard veeeery late in the tube era - actually like 20 years after lol - with late 70s or 80s codes.
But no, I don't believe I've seen Blackburn-made Mullards for those types.
Quick piece of tube trivia on the earliest, almost prototype-like, Philips Holland E88CC. What I just bought is a 7L3 pinched waist tube, made in Heerlen Holland, which is the last batch to actually have that feature. That batch lasted from sometime early-mid 1957 to late mid-late 1958 - which is a long time compared to other batches.
7L2 and 7L3 tubes were made with silver-plated inner wires, which is one of the reason they're supposed to sound so good; most were made in the Heerlen factory, but some 7L2 may have also been made the Eindhoven factory - yeah, that factory that's always in the Philips code lists but never on a tube.
But even before those batches, you could find - virtually extinct now - 7L0 and 7L1 batches made in the Eindhoven plant, and made with gold-plated inner wires, which is supposed to be a part of what makes them so good. People seem to say that both the earlier Eindhoven gold-grid revisions and the later Heerlen silver-grid revisions are top tier; some say that the 7L0 and 7L1 are more desirable, but the few people that actually found, bought and tested both seem to say that they're just different. So the pinched waist "trait" seems more important than the grid material used. Not that this matters since all those tubes are rare and cost a leg.
Much credit is also given to the 7L4 and 7L5 non-pinched waist D-getter E88CC made in Heerlen, but people say these tubes don't quite have the "magic" - hey, I didn't write this you know, people all over the web do lol - the pinched waist versions do.
As far as US-made Amperex pinched waist 6922 go - they're even rarer... - it seems the batches available start a bit later in time and would mostly be 7L4 from '59, maybe earlier. Again, it's hard to even find information on these...
E188CC are a different story. The D-getter, Heerlen-made, ones from the VR0, VR1, and part of the VR2 batches from years late 1959 to mid 1960 are clearly more desirable than anything that came after. Why? How? Not many people seem to actually be able to say, but that's the consensus anyways.
US-made Amperex 7308 tubes follow the same logic: the earliest 1960 D-getter VR0 batch is supposed to be a whole notch above anything that came afterwards and have a "magic" to it - whatever that means. It's ultra rare anyways, but good to know.
Apparently - and I say this both from my experience with the US 6922 and from extensive googling - anything Amperex made in the US beyond 1962, while excellent, just isn't as musical as what came before in the US or in the same time frame in Holland. The difference I heard between a '62 and a '64 US-made 6922 was so striking it kind of convinced me (don't know if gibosi has such a strong feeling about this?).
So, for US Amperex, if you're going to fork the major cash to get something good, either aim for the earliest 7308 in 1960, or the 6922 no later than 1962. Most people on ebay don't seem to have picked up on that huge difference between early and late 60s US 6922 tubes, so whether you buy a 1961/62 O-getter 6922 or a 1966 one, you'll essentially see the same prices. So go for the earlier ones!
Holland production follows the same pattern, but the cut-off in sound quality is more between D-getter tubes until 1960 and later halo-getter tubes. The early tubes are much better, and sadly people know about it, so prices are indecent... But again, if you're going to fork the cash, the earlier the better.
Sorry I'm ranting again, but I figure someone is bound to find something useful in there. At least it save the hours scouting random opinions in pagan languages on google lol...