Well-kept secret?

[maxhifi]

I think the 6V6 made the 6F6 obsolete in most applications by the late 30s.

[David Roper]

Originally Posted by maxhifi

I think the 6V6 made the 6F6 obsolete in most applications by the late 30s.

Maybe, but it seems odd that the 6F6 was entirely superseded while the 6K6 continued to thrive. 6K6 is nothing but a derated 6F6 yet the RCA 630 uses what--five of them (and no 6V6s)?

[maxhifi]

Originally Posted by David Roper

Maybe, but it seems odd that the 6F6 was entirely superseded while the 6K6 continued to thrive. 6K6 is nothing but a derated 6F6 yet the RCA 630 uses what--five of them (and no 6V6s)?

Hmm you raise an interesting point. I was just thinking how sharply the transition was made in radios.. after the 6L6 and 6V6 came out in 1937, the 6V6 very quickly became the go-to medium sized power tube. I can't think of any post-war radios with a 6F6 output stage either, although someone could probably prove me wrong. It would be the exception though, and I also don't know of any hi-fi amps with 6F6 output stages, so the 6V6 must have had some clear advantages.

As for the 630 using a quantity of 6K6's, well, it's anyone's guess. I am sure some very strong opinions existed within RCA at the time, and chances are most of them are lost to time. It's fair to say though that not long after the 630, specialized TV types took over future designs, rather than general purpose radio tubes used in the early sets.

The 6K6 did not endure the same way the 6V6 has - the 6V6 survived in TVs well into the 60s as the 6AQ5, and even lives on today. I was in a guitar store a couple months ago and saw a brand new Made in China Fender Champ with a 6V6 and a 12AX7 in it, for less than $200. That's some amazing longevity, I wonder if someone will still be making 2N3055's in 2043!

[Chad Hauris]

I think the Hallicrafters S-40A communications receiver still used a 6F6 output and 80 rectifier up through the late 40's/early 50's...some of the later models may have replaced the 80 with a 5Y3 but I think they all used the 6F6.