Tube amplifiers sound better as a result of euphonic distortions they enhance the music, along with lots of other reasons. I’ll cover below. These are subtle effects most audible to musicians and extremely dedicated music lovers; casual listeners (those who “listen” with their eyes open while doing something else) usually won’t notice, but sometimes the real difference is so obvious that people’s wives will comment that “wow, that sounds significantly better” whenever people use tubes at home.
Tube amplifiers measure poorly in the lab specifically due to these added distortions, however, these distortions are often a part of what make them sound better. To this day having an all-digital infrastructure from recording studio to SMSL Amplifier for years and decades and decades have used tube pre-preamplifiers in the microphones themselves. Today their outputs are fed to tube preamplifiers prior to being digitised for recording, mixing and distribution. We use tubes since they have the music we create sound better: smoother, warmer and cleaner.
Ditto for guitar amplifiers found in creating music. The ways that tubes distort when pushed to the edge tend to be more musical compared to artificial sounds which come from transistor amplifiers when overdriven. Some transistor guitar amplifiers attempt to mimic tube distortion, but that’s an alternative article.
Needless to say they are all very broad generalizations, and this is simply just as much as a result of circuit designs used with tubes or transistors as the devices themselves, but do you know the distortions and other reasons tube amplifiers sound better?
Tube amplifiers have a lot more distortion than solid-state amplifiers, but a majority of of it is second-order, that is quite musical. That’s why it’s called “harmonic” distortion. Second-harmonic distortion is exactly the same note, an octave above. Ditto for higher-order even harmonics; they are also exactly the same note more octaves above. Even-order harmonic distortion can be so pleasant that in the 1970s the Aphex Aural Exciter was quite popular in recording and broadcast specifically because it was made to produce and add these harmonic distortions! You can still purchase it today.
Not merely is tube amplifier distortion harmonious, it increases as things get louder – just as they actually do in a musical performance. As instruments play louder, or while you hit a percussion instrument or piano key more strongly, they generate more harmonic content. As notes decay, the percentage of harmonic content drops again.
Tube amplifiers mimic this. A good tube amplifier like the Woo Audio WA7 Fireflies increases its distortion directly with output level across 30 years of voltage, or perhaps a million-to-one power range. In contrast, here’s how a typical solid-state amplifier, in this instance a Crown D-75, lowers its distortion with level, and then suddenly clips in great amounts (the nearly vertical line on the right):
Be aware that the Woo graph is with regards to voltage output, as well as the Crown plot is with regards to power. Actually, the Woo plot covers an electrical range of over 6 million to a single, whilst the Crown plot only covers an electric power variety of 50,000 to one. With this particular progressive, “dynamic” distortion, tubes add sharp attacks while retaining long, floating sustains for each musical note.
Just like our ears, musical instruments and almost everything else natural, tube amplifiers have the least distortion at the lowest levels. For this reason a tube amplifier can sound great played softly, while with transistor amplifiers folks are usually being forced to transform it up to have it sound best. Honestly, I don’t bother using my dbx 3BX dynamic expander with a tube power amp, as it adds a lot of dynamic impact.
Mingda Tube Amplifier sound their best at the volumes where you really desire to enjoy them. Just like digital systems, solid state amplifiers measure and sound their worst at low levels, and have their best knhcnt at near to their maximum output levels where no person ever actually plays them. For normal use with normal music at normal levels, most of us enjoy our music at about 1mW ~ 1W long-term RMS, or about .01W ~ 10W peak. For many applications, a 30 WPC amplifier is about right.
What’s sad is that the few consumer magazines that try to publish lab results usually only plot performance down to 100mW, while in fact by far the most relevant power range where we enjoy most amplifiers originates from 1mW to 1W. What will happen below 100mW is really important; that’s right where the majority of our music lives!
Sadly even though you pay $150,000 for a set of overpriced frou-frou solid-state amplifiers, you’ll see its reviewer said many nice reasons for it, but he still said “the better I cranked them, the better they sounded” on page three. So for $150,000 they don’t sound best in the levels I want to enjoy them? Stick to the money; I don’t take ads from manufacturers.
Don’t permit me to stop you if you want Xiangsheng 728A Preamp, but you don’t require it unless you love to crank it, have a big room or inefficient speakers, or enjoy very wide dynamic range classical music at concert-hall volume.