Baltimore
Well-known member
Hi everyone, this is my first post on this forum. I've already learned a lot reading the archives, but I still have a lot to learn.
I'm looking to build multiple channels of a simple single tube preamp. I'd post a schematic but I dont have anywhere to host one. It would basically consist of a 1:10 input tranny to the grid of a 12ax7, around 300v B+, 150k grid to ground (as jenses suggests for the jt-115k-e) 220k Rp, around 1k for Rk, 2uf cath bypass cap. This direct couples into a cathode follower with 100k Rk then a cap coupled 2:1 output transformer to drive a 600 ohm load. If my calculations are correct I should net about 50dB of gain, which should be plenty for what I'll be using them for.
My main question is this: where should I put an attenuation control? I'd like it to be adjustable, either switch or pot, but I don't know the best place for it. Any tips? Before the input transformer? between the gain stage and CF, after the CF?
Also, anyone see any drawbacks to this design?
-Kevin
I'm looking to build multiple channels of a simple single tube preamp. I'd post a schematic but I dont have anywhere to host one. It would basically consist of a 1:10 input tranny to the grid of a 12ax7, around 300v B+, 150k grid to ground (as jenses suggests for the jt-115k-e) 220k Rp, around 1k for Rk, 2uf cath bypass cap. This direct couples into a cathode follower with 100k Rk then a cap coupled 2:1 output transformer to drive a 600 ohm load. If my calculations are correct I should net about 50dB of gain, which should be plenty for what I'll be using them for.
My main question is this: where should I put an attenuation control? I'd like it to be adjustable, either switch or pot, but I don't know the best place for it. Any tips? Before the input transformer? between the gain stage and CF, after the CF?
Also, anyone see any drawbacks to this design?
-Kevin