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Patrick Turner Patrick Turner is offline
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Default What is this matched quad of new RCA 6L6GC tubes worth?

On Saturday, 1 September 2012 14:02:50 UTC+10, JimK wrote:
On Friday, August 31, 2012 9:23:50 AM UTC-6, JimK wrote: I want to sell these to help finance buying a new amp. Looking on Ebay I see they are not the holy grail RCA which are the black plates. Mine have gray plates, the flashing on top not on the side, RCA is on the glass, not the base, and 6L6GC is on the glass but not in the stop sign like the black plates. They are really new, given to me by an engineer in the research lab I worked in in 1990. The boxes (red and white, not red/white/black like black plates) are new, and the pins are obviously new. So I'm disappointed these are not the holy grail tube and wonder what they are worth? Are they close to as good as the black plates? If they won't bring much maybe I should keep them for my McIntosh and Fenders if they are better than new tubes? Thanks for your advice. These are new. I can include a link to a youtube video of them being tested. Would that help? But I don't know how to do that, ebay prevents links. Thanks.


The trouble with buying NOS tubes is that a buyer faces the prospect of having one or more of them failing from bias failure prematurely after using them in an amp. So that leaves a buyer without any matching spares. I service tube amps and I've witnessed the troubles ppl have with NOS tubes which ppl claim are new, but in fact they may have been made in 1960, so they ARE now 52 years old! If this quad of tubes is so good, why sell them? why not use them? And the claim you make about selling to help pay for a new or another amp is BS because tubes are not the major cost of a decent new amp. If ppl want a quad of NOS, they always should buy 6, to allow for duds.

I've seen blokes buy NOS 6SH7 and 6SN7 and 6SL7 which are in the packaging specified by the military and they were made in 1941. The last batch of about 25of these tubes someone here found on E-bay yeilded about 6 good ones. They were all 71 years old. But old blokes don't like to face the facts about old things, or that they themselves have aged, and that they have become a parody of what they might have been once. I found that most of these NOS 1941 tubes were noisy, hummy, microphonic, or gassy or had all problems possible.

Another customer gave me a suitcase full of tubes previously owned by a relative who was a radio serviceman. This was to help finance the restoration of an old floor stander radio he had. I find 121 tubes in the suitcase. Many are from 1930s, and a few suited the 1935 radio the guy wanted fixed. Most boxes looked new, but tubes inside were mostly old pulls, emission was not as good as existing tubes in the radio. It took me a day or two to go through and list all and find space to store the ones that looked OK, but all in all the gain of a suitcase fulla tubes was quite negative; accepting such a gift was in fact a cost, and I could not discount the cost of restoring the old radio which needed complete rewiring and re-design which could not have been achieved using more old type tubes. And in future years, there sure won't be any more around because blokes who do have a good stock of old tubes to riffle through to find good one will all die and relatives chuck out his stocks as rubbish. It seems only real old guys have stocks of real old tubes. Better for me to rewire an old radio for an EL34 or 6L6 (still being made) in triode mode than try find a replacement 6F6 which won't sound as well.

But I don't think NOS power tubes are always better than those made by the Russians just because the yanks are too lazy to get on with it. And I hear no reason for ppl to pay hugely for nostalgia. The input and driver tubes are just as important as the output tubes when it comes to sound. I have also seen and heard an ST70 which had 4 different brands of EL34 in it. Sounded fine after I re-wired it. Not only that, most OLD USA made amps sound better when they are rebuilt with parts the bean counters would not allow into the amps; its not the tubes alone that set the sound quality, its the way the amp is designed.

I have pair of RCA amps on my bench awaiting the Big Singing Lesson. They are nice looking monoblock amps. They look like classic amps, each with 3 identical cases for potted mains tranny, choke and OPT inside, and looking like what would now used for an AB 100W amp. They are only 30W though. One has old and probably stuffed KT66 and other has old 6L6 and the ancient owner bought one in 1960s for mono sound, them a second one later when he went to stereo. Probably tubes are original, and why they were parked remains unknown, could be fused OPTs from failing OP tubes. But the guy changed to SS some 30+ years ago. They are very dirty inside and out, covered in dust and neglect after being parked for so long. If iron is OK, what will make them sing is replacement of all the tubes, and rewiring internally with all metal film R and polyprop C and my own circuit using 6CG7 instead of the pair of EF86, which BTW is very like Dynaco. Probably Dynaco copied the RCA circuit, but I don't like it. There is better to be had.

Patrick Turner.