Hi rc,
Yes you're right. Tube mics require a higher voltage than the normal 48 volts to charge the tube. That's why they have an external power supply.
And yes, you will need a mic pre. Occasionally you'll find a tube mic that gives a line level out, almost all are mic level out. Also, once in a while a hot output tube mic, when recording a high level signal can produce a near line level signal. I've had that happen with a few time recording a bass amp with a U47 and amazingly a singer using a Brauner mic. All that to say, if you're recording something that has you pad the mic pre all the way and it still isn't low enough, you can try putting in the line input. Sometimes I'll do that, other times, I prefer what the mic pre does.
That may be more info than you asked for...but I hope it helps.
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DAS
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