Since it's not a production amp, no need to post anything but the initial impressions of my "new" Vacuum Tube (VT) amp against a solid state (SS) amplifier in what I hope is a controlled environment.
The background story is I got a vintage Westinghouse turntable that was pretty much destroyed. I pulled out the tube amp and made all the necessary repairs to make it make sound. Just stuff like cleaning the tubes with water and soldering a bit here and there. There's moisture damage. Every part on the amplifier is almost undoubtedly older than every member on this forum. (Man it feels good to say that! =)
It's competitor is an SS amp. A Mobile Authority M103A amplifier, which attached to a 1 amp power supply makes quite the headphone amp. I should mention I need more repairs to do to the VT amp. There is a LOT of noise. I continue the test regardless, having no means of correcting this yet.
The first test is general SQ. I basically just fire up XMMS (Winamp for you Windows users) and play random songs through each amp. The SS amp performs about how I expected. The extra power makes for an improved bass response, snappier midbass, and everything is a little clearer. It also made everything distinct, in a way. I don't know how to describe it, but *everything* stood out. Almost like every instrument was recorded on it's own and they are just being played one on top of the other. The harsh highs were very harsh. Unbearably harsh at times. It also brought out every flaw in any MP3 encoded at less than 96KBPS. The sounded muddy and distant. Like I was listening to them through a piece of cloth.
The VT amp is a little different. It just sounds.. different. The bass is fuller and lower. Nothing like magic, just there enough to take note of. The midbass stands out a little more. It's very difficult to describe just how it sounds, but it's very pleasant. Everything blends together more like I think music should, which was a big disappointment with the SS amp. The mids are very clear. Unlike the SS, the highs were smoothed out a little, and while the harsh highs were still harsh, they were bearable. Going to the low bitrate MP3s almost was like magic. It brought out everything in them. I can hardly tell they the difference between them and normal 128KBPS mp3s with the VT amp, and not in a bad way.
The second test is for introduced noise. This is important because headphone amps are usually very close to a PC and CRT monitor (Can you say EMI?). The SS amplifier performs right about where I thought it would. It is very susceptable to noise. Just moving it closer to and away from the monitor causes a big loss and gain of distortion.
The VT amp surprised me. Dispite the large amount of noise created by the amp itself, it is basically impervious to the EMI caused by my monitor and PC. The amp is quite literally touching the monitor as I'm typing this, and the THD could care less.
No contest. The SS amp takes home the trophy, pushing roughly 6 times the power of the VT amp.
Vacuum Tube > Solid State. In a great many aspects I just like the sound of the vacuum tube amp better. The only way I can think of describing it, is that the solid state amp is trying too hard.
When I did the SQ test, I kept the SS amp close to the monitor. Enough to keep the noise level about the same as the VT amp. I know someone will want to bring this up and say that having a buzzing problem puts the VT amp at a direct disadvantage (Making the preference a really big deal), but it didn't.
The VT amp was cheaper that the SS amp in my case. Normally VT amps have the worst dollar to watt ratio of any type of amp in existance. I'm sure this would change the review knowing so much money was on the line. Sad but true. The Mobile Authority amp cost me $40, the Westinghouse has $21 in purchase and repairs so far.
If I could have level matched the output between the amps, it would have been a fairer test. I can guarantee you the SS amp was pushing far more power. See it as you want, both amps were overpowering my test headphones by a factor of 10x to 20x. They are, or were, $10 Sony earbuds from Walmart. In the tests the right earbud popped once and now crackles with certain frequencies of midbass. =\