I scored a Little-Bear single tube pre-amp on eBay for a little less than 20 bucks shipped ($1.79 bid + $16.95 shipping).
After 2 weeks of waiting, it arrived from China today, some assembly required. No soldering, though: the only tool I needed was a screwdriver.
By the time I finally got a chance to play with it, my daughter had gone to bed. So my impressions tonight might not be the same as when I get to play with it at louder volumes. Be that as it may, after letting the tube warm up for about an hour, I plugged my phone into it, then ran its output to the aux in on the front of my receiver. I then cued up the same song on my phone and on my receiver's uPnP client player. I flipped back and forth a few times, trying to get an idea of what I was hearing.
Firstly, after very un-carefully and un-scientifically matching volumes of both sources by ear, I can safely say that this little gadget has no gain. Indeed, with the volume knob turned up full, there's still about a 10dB loss it seems.
But in the midrange, vocals move forward. There's an emphasis applied to vocals, baritone through soprano. Also, throughout the entire range there sounded like some phase variation that was pleasing for the most part. It had an unfortunate effect on sibilance, making S's harsh and unpleasant. (In retrospect, that might have had more to do with my phone's volume being too high than with any tube effect. I'll have to experiment a little more later.) Harshness aside, the EQ didn't sound wrong.
After listening through this tube pre-amp then going back to pure digital, the digital source sounded more accurate, more mechanical, more formulaic, less artistic and a little too perfect. The tube had a sort of live performance quality, a little imperfection that gave the sound character. It's not an audiophile device by any means, but for less than 20 bucks, it's a fun toy.
