Tube Preamp Schematic of Preamplifier with Direct Heated 112A Triodes
The 112A is one of the quite popular small-signal US prewar direct-heated triodes. With its small internal resistance of 5k you can match with a line-transformer.
Although the Hasimoto A105 is a interstage-transformer it works very good when wired to a 1:0,5 ratio. The parallel 620R-resistor allows a little tweaking of the sound.
Not easy to handle is the sensitiveness against hum and microphony. You need a shielding especially between the rectifier-tube and the triodes.