The ups and downs of tube vs. SS...

Most audiophiles care about their systems, and tubes provide that "Zen and the Art of Motorcycle Maintenance" ethos that allows interaction and care of a quality product.  In contrast, solid state is something you bought that just sits there.  

I also think the soft clipping of tubes is kinder than the brittleness (ugly harmonics) of solid state when it gets peaks that exceeds its range.

Speaking of hybrids and Vincent, I’ve had my SP-331 stereo amplifier for over three years and couldn’t be happier. I’ve tried more than a handful of different amplifiers borrowed from friends and family, some a lot more expensive, and this amplifier compared well against most of them at least in my system. One obvious exception was when I put in my brother’s Bryston 7B-ST monoblocks and they buried the Vincent. A tad bright for my taste but the overall detail and the added bass was quite impressive.

I am a tube guy for quite while. I'm like to read articles concerning human hearing & perception of sound pressure levels and the effect of different levels of harmonic distortion on human hearing. Any suggestions?

There is precious little about this specific topic- for example GE's study is not online. But you don't need to read anything if you have the right test equipment- a sine/squarewave oscillator (as opposed to a generator), an amplifier of any kind, a speaker and a VU meter.

Set the oscillator to sine and drive the amp through the speaker. Put the VU meter in the circuit and set the level at 0VU. Then cover up the meter, and switch the oscillator to 'square' and set the level so it sounds at the same level as before. Uncover the meter, and you will see how much more sensitive our ears are to the higher ordered harmonics!

The tube amp sound less fatigue than SS and the impulse/dynamic is simply great. The only thing is that in the low end the energy is that strong as a SS.

If you want the bass energy in the tube amp to be right, the bass range of the speaker should be as high or higher than that of the mids and highs. Also, you will want to avoid 4 ohm speakers- with almost any output transformer, there is a loss of low frequency bandwidth driving from the 4 ohm tap as opposed to the 8 ohm tap (plus the amp will be smoother and more detailed driving higher impedances, which is true of **all** amplifiers). Also, keep your speaker cables short (under 7 feet!) and the connections at either end tight.

One obvious exception was when I put in my brother’s Bryston 7B-ST monoblocks and they buried the Vincent. A tad bright for my taste but the overall detail and the added bass was quite impressive.

@kalali Just think if you found it a tad bright now how you would feel after an extended audition? Even that extra detail can start to wear and just not with SS amps. I had a pushpull 45 amp on loan when Deja Vu was recapping my amp and I found it too detailed. All the details were making it hard to focus on the music.

I like tubes as well. Keep in mind however that not all tubes sound good. You can't just buy any tube amp/preamp and expect good sound. Not sure what your interests are but for others a good starting point is a single ended amplifier with appropriate speakers. Beware small tubes and beware tubes that produce lots and lots of power. Don' get more power then you absolutely need. Make those little tubes work a little bit.