• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Need Suggestion for Input Stage For Power Follower 99

Any medium mu tube--12AT7, 12AU7, 6SN7, 6DJ8, etc.--will give you a 15V swing with a reasonable (1-2V) input. Hi mu tubes such as the 12AX7 will easily swing even more. If you're wanting Zout 1k or less, you'll need a cathode follower. No big deal there, either. So, if you're wanting a tube front end you could easily use the two halves of, say, a 6DJ8, the first as gain, the second as a follower. 150-200V rail, 10k plate resistor, 200 ohm cathode resistor. This will run out about 25-28 dB gain...more than enough. Burn any surplus gain as feedback, or use a smaller plate resistor to reduce the gain. For a cathode follower, use Rk 10-20k or so, same rail, and you're done.
If you want to go solid state, any of the Zen variants will do just fine.
If you want to get fancy, set the front end up as a differential and use the backside as the feeback input point.