It’s always interesting to try something new – especially vacuum tube. Sometime you can get something from unknown thing.
I’m quite sure we are familiar with 6SN7 vacuum tube, which is commonly used in pre amplifier and even a lot of amplifiers are using this tube in input/driver section. Not surprisingly to see the price is sky rocketing, especially the red base 5692.
I just realize that I got some old tube which is “compatible” with 6SN7, but with different base. Here we go, the RCA 7N7.
RCA 7N7 is practically an 6SN7 in Loctal socket, instead of common Octal socket used by 6SN7. Loctal socket might not be too familiar for most of us, but it’s widely available. We can search the socket in ebay.com at really affordable price or for premium option, we can always go with Yamamoto Teflon Tube Socket.
Be noted that even this tube has “7” prefix, it actually has 6.3 Volt filament. The same applies to 14N7 which is using 12.6 Volt filament. It’s different with let’s say 7DJ8 which is using 7 Volt filament supply.
There are some other tubes with this kind of “exception”. Another example is 1A6 which is using 2 Volt filament (if I remember correctly, most tubes with 2.0 Volt filament will be using “1” prefix, while “2” prefix will be used by tube with >2 Volt filament, example: 2A3 which is using 2.5 Volt filament supply).
Anyway, it’s up to you to use 7 Volt as sometime higher filament voltage could alter the sound (some people likes it).
This RCA 7N7 is a tube with metal base (which sometime I prefer over plastic base). Sturdier construction I would say.
Below shot was taken with my Nikon D90, Sigma Macro 150 mm F/2.8 lens, and two remote controlled flashes (Nikon SB-800 and SB-900).
The tubes itself has some sort of punch “stock control” card. An interesting way to see how this kind of stuff was taken care at that time (somewhere on 1966).
It would be interesting to see how this tube will compare with most 6SN7 and probably with the famous 5692 red base – if I can get some!