Originally Posted by atbglenn
Even when these RCA's were new, they didn't sound harsh or muddy. Are yours the same as these? Note the shield between the plates. I hear some don't have them. I'm not sure that makes a difference though.
Back to the RCA 6DE7 discussion...
I got another set of RCA's. I bought them off eBay as "NOS". When I got them... well, it was like a box of chocolates as Forrest Gump's mother would say. They are the tubes that are shown in the picture two posts above this one.
The boxes are like new, and are date stamped 09/60. The tubes sound great in my amp, and I was pretty happy until I did a closer inspection. One of the tubes has the RCA logo and has the two plates with the shield. The other tube has no brand logo (completely rubbed off) and has the cross-style second plate with several perforations and no shield.
The tube with no brand logo is stamped 6DE7, but it does not say "U.S.A." above it like the RCA does and the size of the "6DE7" is slighter larger than the same printing on the RCA. The tube with no logo does not have the black box at the top of one of the plates like the RCA does, instead it is finished with a smaller thin black square like my Sylvania.
I suspect, given the condition of the boxes vs. the tubes, that this was a tube pull. Someone probably pulled all of the tubes out of a unit, threw away the shorted one, and put the remaining old working tubes back in the new boxes. Tube pulling was a fairly common practice for TV's, as the service call was more than the full set of tubes and people were happy to pay for a new set of tubes to avoid having to call the serviceman back in a month. If one tube went, the rest were bound to go soon - at least that was the logic at the time. Many servicemen held on to these old working tubes to be used in an emergency to keep a customer going if they were out of stock on that particular new tube.
Anyway, if my theory is correct, these recycled 6DE7 tubes ended up in my hands. That being the case, they would be used but also probably older than 1960.
Is it possible that the tube without the shield is RCA also? Did they make both styles? This goes back to atbglenn's point that I quoted above. The construction looks like my Sylvania tubes, but maybe they are some other brand or RCA's made for someone else.
RCA or not, should I be happy to pair these tubes together if they sound good together? I don't see how it could harm the amp, and the sound is the ultimate grade card.
I don't plan to return them because the seller and I reached an agreement over them not being "NOS", whereby I would keep the tubes and receive a refund of the auction price less shipping. I am happy to pay this small amount for spare tubes and new boxes, but I am considering whether to use them.
Thanks for any help that the other 6DE7 users could give me in clarifying the questions above, particularly whether this tube might be RCA and should I have concern about using them together.