The SFL-1 is indeed tube, but not ALL tube. The signal goes through a Burr Brown analog volume control integrated circuit. It's used only to attenuate, not for gain. But if you're seeking true 'tube' preamps, I'd look elsewhere.
That said, I did own a Line 2 for a few years. It's a good sounding unit. Is a BAT preamp in your price range? That would be my recommendation. All tube, balanced, detail, warmth, low Zout. I also owned one of these; quite an improvement over the Sonic Frontiers.
That said, I did own a Line 2 for a few years. It's a good sounding unit. Is a BAT preamp in your price range? That would be my recommendation. All tube, balanced, detail, warmth, low Zout. I also owned one of these; quite an improvement over the Sonic Frontiers.