Stop agonizing over 10:1 ratios & other misinformation. Try it & you`ll probably be pleasantly surprised.
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The general rule is 10X or greater. That is not misinformation but it is a guideline, not a law. The lower the ratio the more voltage is dropped across the output impedance of the source and the max volume will be reduced. It can also affect the frequency response by rolling off the bass especially if the output is capacitively coupled as most tube preamps are.
You are closer to 100X so that should be fine.