I have attached a schematic for a Fisher preamp. It uses a 12DW7 / 7274 in the final stage. The high mu section is the first triode and the low mu is used as a cathode follower.
As I understand it, the gain is developed in the first triode and the cathode follower is close to, but just under, unity.
If my understanding is correct, then that begs the question, why not just use a 12AX7, since the mu of the second stage is not really coming into play?
I'm sure there is a good reason and I'd like to be let in on it.
Thanks
As I understand it, the gain is developed in the first triode and the cathode follower is close to, but just under, unity.
If my understanding is correct, then that begs the question, why not just use a 12AX7, since the mu of the second stage is not really coming into play?
I'm sure there is a good reason and I'd like to be let in on it.
Thanks
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The 12DW7 is 1/2 'X7 and 1/2 'U7. The 'U7 section makes for a tolerable cathode follower.
If you are willing to work hard at reworking the layout, installing 'X7s and 'U7s may be feasible.
No, a 12DW7 is not that hard to come by. It's the understanding I'm after.
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