We've talked about the PA-10 before, but only recently have we had a chance to lay our ears on one at Retro Thing labs. It's made by Trends Audio, the same folks who also offer an audiophile version of the famous T-amp amplifier. The PA-10 is the same compact size (about the size of a couple of cassettes stacked up), has the same simple controls & few inputs... but the difference is apparent right away. There's a blue-glowing tube sticking out of the top (and you know how we feel about blue glowing things).
You connect your audio source to one of two inputs on the back (with a small switch to select between the two inputs), and then plug in your headphones to the 1/8” jack on the front. The big friendly volume knob on the front and blue power led completes the ensemble and off you go.
My tests were very straightforward. No oscilloscopes or test signals; just my ears, some favorite music, and a couple very good sets of headphones. I chose to play tunes from a tabletop CD player with an 1/8” headphone jack as well as a good portable CD player. That way I could compare the sound coming right out of the CD player versus what it sound like after going through the PA-10. I also played some MP3's directly from my laptop. Some were seriously compressed, others only mildly so.
After much back and forth, my overall conclusion is a simple one. Music played through the PA-10 sounds much better. In audio gear reviews, people will talk about how true the sound is to what the the artist originally recorded (which is why some audio nuts I know actually dislike adjusting the sound via an equalizer). Whatever the tube might be doing to color the sound, the music had a much improved stereo sound stage, and was far more vivid overall.
Whenever I upgrade audio equipment (especially headphones), I'm looking for a dramatic difference to what I had before. The PA-10 brought a dramatic difference to music I've heard hundreds of times. It was exciting to pull music off of the shelf to hear what it would sound like with the PA-10. I've bought equipment that was much more expensive (and bulky!) than the PA-10 that offered a much less dramatic improvement.
The PA-10 lists for $225, which is pretty approachable for “audiophile” gear. It's also a good way to enter the world of tubes. Swapping around different tubes to get a favorite sound is almost a sport among analog audio fans. It ships with a Chinese 6N11 tube, but you can substitute a Russian 6H23n or American GE 12AU7 for an extra $40.
The simplicity of the PA-10's board layout encourages DIY type hackery, and there are online forums discussing all sorts of ideas for tweaking its performance, which is a big part of the fun. There's also a simple jumper to skip the volume knob if you want the purest performance from this little amp.
One thing that would make me happier would be a phono pre-amp in the unit. I have so many records that I want to digitize to my computer, and it would be a great advantage to have a compact and great sounding pre-amp running the show. A pocket sized tube amp with a great build is a unique product that can make that old music sound a little more lively again.