Solid state amp vs tube amps

One of the major factors on whether a tube amplifier sounds different than solid state is how well the respective amplifiers can generate increased current into low impedance loads. If the amps are connected to speakers that have low sensitivity and a demanding impedance curve the two types of amps will likely sound quite different.

First example is driving speakers like Wilsons or Thiels that can dip to around 2 ohms over part of their frequency response. These speakers were designed and voiced to be powered by beefy amps that can double their power with each halving of the impedance. My Krell KSA 300s puts out 300 watts into 8 ohms and 2400 watts into 2 ohms. It is driving Thiel CS6 speakers that dip to around 2 ohms in the mid bass with a demanding phase angle. A typical tube amp will simply not be able to drive these speakers so that they have a flat frequency response. In the frequencies where the impedance drops to a low level, the amp cannot provide the current to drive the speakers.

Second example is driving speakers from a company like DeVore that are designed to have a flat impedance curve and higher sensitivity. There are also many horn speakers that have this characteristic. For these kinds of speakers a high quality tube amp and solid state amp will sound much more similar.

My point is that besides the pleasant sound that some people ascribe to tubes, there can be a large frequency response difference between amplifiers depending on what type of speakers you are driving. You will never see a pair of big Wilson speakers driven by an SET amp at an audio show. They are driven by monster amps typically from D'Agostino. They were designed and voiced using these amps and they were willing to accept the high current requirements to achieve the sound they want. One can argue that tubes have more "bloom" or whatever, but there can be large, measureable, frequency response differences depending on what amp you use to power speakers with a demanding impedance curve.

@marquis4099 Yes, you will notice a difference, but it may not be as great as you think, and ‘better’ will be a judgement you’ll have to make. 
 

My experience: bought the best solid state and tube gear I could afford, some of it, just barely, assembled two systems in the same room, and after two weeks of listening I still couldn’t tell you which I prefer. They sound almost identical, the difference coming down mostly to the speakers and their placement in the room. I did notice, though, that when I swapped in the latest component —a top-of-the-line tubed preamp— that the mids and highs were super smooth compared to the entry level solid state gear it replaced.
 

Many say that it is relatively easy to build good-sounding tube gear because most (but not all) of the magic is in the tube; it is very difficult to build solid state gear to the same sound quality without going to expensive parts and meticulous construction. Others say that all tube gear produces distortion and that they are not worth the bother or additional expense of periodic (or emergency) replacement. You’ll just have to make up your own mind.

If you’re trying to decide which way to go, I wouldn’t go with tubes unless you’re comfortable opening up the case once in a while, making adjustments, and replacing tubes, either because you need to, or you just want to see how other tubes will make your system sound. 

No one has mentioned the output impedance of tubed amps vs. that of SS amps. The higher impedance typically found in tube amps makes them more load dependent, and can introduce audible variations in system response based on the speaker’s reactance. In my opinion this phenomenon accounts for much of the mystique around system synergy. It is said the McIntosh MC275 has an unusually low output impedance and therefore sounds more “solid state” than other tube amps. 

Interesting nobody brought up noise.  Solid state amps on average are quieter.  You have to spend a lot of $ to get tube amp with a signal-to-noise ratio over 100db (particularly all-tube integrateds).  So for those whose aural priorities start with noise, they usually prefer SS.  Me? I’m a tube guy.

@marquis4099 

In the last fifty years or so, I have had Tube class A, SS class A, SS class A/B, and several Hybrid amps and preamps.  The preamps were all Class A’s and the Amps were all Class A/B.

Right now I have a Hegel H390, that’s a SS class A/B integrated amp. (The first integrated amp I’ve had in 35-40 years) and a PS Audio, BHK Signature preamp with PS Audio BHK 300 mono blocks. Both are hybrid. I have started tube rolling yet, but will probably do so.

 Hegel is somewhat on the warm side and sounds really good with all kinds of music. It’s dead quiet. The highs are crisp without being sharp, the mids are very good, but I find tube amps excel with voices and the like much better and the Hegel has plenty of clean low end punch.

I’ve only had the PS Audio gear a couple of months. The Amps were bought used and came with 7308 input tubes. In my experience, 7308’s are really great sounding tubes, but are definitely brighter sounding than 6922’s or 6dj8’s. I’m going to replace the 7308’s with some 6922’s and see if the sound is more to my liking.  So like the Hegel, this setup has a great bottom end a very good mid range and I’m going to tube roll until I het the sound I want. The input section on the preamp can use 12au7’s or the 6dj8 line of tubes, so there’s the place I will probably start with seeing as I have many 6dj8’s and 6922’s to choose from here.

One more thing, the Hegel is stable down to at least 2 ohms and probably lower. 

All the best.