ampllifier design

I likewise have good associations with the 6CG7, it's the long-tailed-pair phase-inverter tube in my Marantz model 2s . . . it's used effectively for this role in the 5 & 8 as well, and as a cathode-follower in the 9.

But if you're using EL84s as outputs, then the 6CG7 is kinda overkill as a driver tube, and you might have a problem making it work at its best as a long-tailed-pair from the lower B+ plate supply (Marantz had a higher B+ available because he was using EL34s as outputs). And for an input tube, the 12AX7 is a better choice because of the higher mu.

I personally don't feel that different tubes themselves have any "sound" at all - it's the circuits that they're used in that have certain "sounds" . . . and it's just that some tubes are traditional choices for certain circuits, and thus we have these associations. I also think our associations of NOS tubes as "sounding better" is because their manufacturing tolerances were much, much more consistent, so it was/is possible to make more precise engineering decisions about critical circuit parameters. Added to this is the fact that most of our tube data is NOS as well.

Interesting post, Atmasphere.

It might have been yet more interesting had you noted that you yourself used the 6DJ8 and 6CG7 in earlier versions of the MA-1, and then explained how you later came to the realization that these tubes did not provide the best performance.

Hi Jimjoyce25- bingo! We got great linearity out of them, but they would often ring like a bell. Handpicking them got the microphonics down, but never to the point that you can get with a 12A* series tube or 6SN7. I'd always been a fan of the 6CG7, but when I realized that it and the 12AU7 were evolved from the 6SN7 geometry, I decided to try the 6SN7. There was no looking back at that point.