Even a 1-watt tube amp (a 12AU7 in a current amplification configuration will put out about this much power) will be too loud for bedroom-level use when it's turned up. Power to apparent volume ratios are on a logarithmic scale -- in order to get half the volume of a 100-watt amp, you need a 10-watt amp.
Now, big tube amps with Class AB push-pull power stages can usually be turned down to very low levels, but when you do that, they become Class A amps, and a lot of players don't like that sound -- it's looser in the low end, and there aren't as many odd-order harmonics, so the amp won't sound as big and punchy as it does when it's turned up. A quieter amp won't anyway -- part of the sound of an amp up loud is actually in your ears.
There are some suggestions to use a solid-state practice amp. That's not a bad idea, as your problem is what those are meant to solve. A solid-state amp will sound pretty much the same no matter where you set the volume knob, but it's going to sound more like your tube amp turned down low, but without the even-order octave harmonics. My suggestion would be to turn down your amp's preamp gain, and turn up the bass, midrange, and treble as you decrease the master volume. It won't sound exactly like it does turned up, but it'll be close enough for practice if you're not too worried about the tone.