These preamps use vacuum tubes to process and amplify the microphone’s signal. This generally adds some coloration to the sound of your mic (how much and what kind of coloration depends on the particular preamp). Digital recording aficionados love the sound of tube gear, especially tube preamps.

The advantage of a tube preamp is that it can add a warm sound to your mics. The disadvantage is that you often can’t get rid of this colored sound. Professional recording engineers often have several tube preamps in their studios to give them different coloration options.

The preamps that are included in your mixer are solid-state. If you find that you want the colored sound of a tube preamp, you need to buy an external one.

Tube preamps are great for imparting a subtle low-frequency addition to the sound of the microphone signal. Tube preamps also seem to slightly soften the higher frequencies. If you’re like most people, you’ll like the addition of a tube preamp, especially if you intend to record rock, blues, or acoustic jazz music.

The downside is that all-tube preamps are expensive, with the least expensive costing about $1,000 (the Peavey VMP-2 — no longer made but you can find them used) and most running several thousand dollars (brands like Manley Labs, for instance).