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Tube warmth and distortion and it's pros

Discussion in 'Sound Science' started by silverears, Apr 13, 2014.
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  1. SilverEars
    I hear a lot about tube providing warmth.  Does tube typically provide stronger low end?  This is what I read, that SS amps are thin sounding.  
    Also, the tube distortion is 2nd harmonics? Or 3rd.  How do these harmonics affect how we perceive the sound?   Some say it's desired.  What does that do to the signal and in the result the sound?
    What are the benefits to tube amps?
  2. ieee754
    I'd rather ask, what tubes do that cannot be done with transparent SS amp and DSP effects (like EQing bass and introducing distortions).
  3. bigshot
    If you are going to ask what tubes can do that solid state can't, the answer is "nothing". Bob Carver conclusively proved that.

    Generally, tube amps sound "warmer" than solid state not because they have better bass, but because the high end is rolled off. Higher frequencies are more difficult for tubes to reproduce than lower ones. Not all tube amps roll of the high end... better tube amps can have a pretty balanced response... but that is a fair overall generalization you can make.

    The best tube amps perform almost as well as solid state and sound just as good. Personally, I would rather just adjust my response using an equalizer and not have the bother of tubes to deal with. I just want a neutral amp. I can add the spice with EQ at the last step.

    As for distortion... no thank you.
  4. rhythm is life
    The main benefit to a tube amp is distortion. If someone is looking for a non-flat frequency response, it can be achieved for much less money through an equalizer. 
    There are people out there that prefer a distorted sound to a clean sound. This is common among bassheads and modern hip-hop fans (maybe not on Head-Fi, but among the general Beats-loving public). Take 2 headphones with the same low-end response, but headphone A has 10% THD below 100Hz and headphone B has 1% below 100. Headphone A's bass will sound louder because the distortion is essentially adding noise to the bass. A lot of recently produced hip-hop beats actually have a lot of harmonic distortion, presumably to create the impression of bass when played back on systems that have a weak/rolled-off bass response. I might not be able to hear a 50Hz fundamental note in my stock car stereo, but the 100Hz first harmonic will come through loud and clear!
  5. bigshot
    It's ironic that tube amps are popular among audiophiles listening to classical and jazz, and the typical hip hop fan generally buys cheap solid state!
  6. 00940
    Tubes have no problems reproducing high frequencies, where do you get that idea ? 20khz is a walk in the park for any commonly used tube. High-end roll-off exists in very bad designs (driving the input capacitance from high impedance sources) or in designs using bad transformers.
    It's worth looking at the frequency response of the little starving student hybrid, in which an input tube stage is used to color the sound: http://www.pmillett.com/starving.htm (scroll to the bottom). This is a quite tubey/warm amp.... and it's maybe 0.1db, 0.2db down at 20k (and it might be a common measurement artefact).
    Warmth in tube amps is more directly related to the fact that a lot of topologies used in hifi are of the single ended/no feedback variety, generating highish content of second distortion, as exemplified in the same link (second graph from the end).
  7. bigshot
    The type of rolloff I've seen described as "warm and analogue sounding" operates well under 10kHz and it was in power amps for speakers. Maybe it's deliberate, but I can't imagine why anyone would want that. But I can't figure out why anyone would want to add distortion, no matter how euphonic it is, to their music.

    Above 14kHz nothing really matters, because there isn't anything of any value up there in recorded music.
  8. 00940
    Then no tube amp, even very badly designed, will ever give you this kind of frequency rolloff. Really, you should forget the frequency response explanation for tube sound.
    And to answer your question about euphonic distortion... well the answer lies in the definition of euphonic [​IMG]
  9. elmoe
    Oh, and in on yet another sound science tube thread.
  10. 00940
    No tubes don't typically provide stronger low end. Quite the contrary. They generally need either  a capacitor or a transformer at the output and are often a few db down at the very low end.
    Distortion spectrum is a matter of the topology used in the amplifier. For some reasons, the single-ended topology is most common in hifi products, especially headphones related. This topology gives a dominant H2. But you also encounter amps using push-pull, where H3 dominates, giving a perceived more dynamic sound. As most tube amps don't use feedback or very little (not enough open loop gain in most simple topologies), distortion is mostly made of the first harmonics, which the brain doesn't object to too strongly.
    The benefits to tube amps... depends. No, really, it depends a lot on the topology/tubes used and what you're after. One can easily taylor the sound. Main reason we still have tube amps is that we can. Since they're naturally quite linear, it's also easier to get decent sound from tubes with simple topologies. Transistors and jfet require more thinking.
  11. bigshot
    I guess if all you listen to is music with electronic/amplified instruments, a baseline in accuracy isn't important. But I listen to classical and acoustic jazz. There are some Frank Sinatra remasters where I'm sure they used a harmonizer to beef up the plucked acoustic bass and extend the response down an octave lower. It's certainly euphonic. It sound nice and full like a brand new digital recording. But it doesn't sound anything like a real plucked acoustic bass. It makes me want to chuck the CDs like a frisbee across the room.

    I don't object to musicians using tube amps on their equipment and adding distortion creatively here and there. But I don't want distortion applied like wallpaper across every recording I listen to. I suppose if my 5:1 system had a DSP that precisely recreated the sound of a good tube amp, I might use it as a novelty for some 60s electric country music, or perhaps 50s rock n roll. But I would never want that on classical music. Swapping between tube and solid state amps on my speaker system depending on what music I was listening to, just isn't practical.

    Tubes have a purpose. I'm not saying they are evil. But my whole goal in my system is to create realistic sound... sound that is present and balanced and clean. I want to hear exactly what the engineers who mixed the music heard. Ideally, what the instruments themselves sounded like in real life. That goal and euphonic distortion don't go together well. I want to remove as much of the sound of my system as I can and leave just the music. Solid state amps do that... a wire with gain.

    And solid state doesn't require any thinking at all... I go to Amazon and buy any midrange amp. They should all be pretty much transparent. Solid state amps that AREN'T flat and clean are the exception, not the rule.
  12. 00940
    It's been quite a while I resigned myself to the fact that most recordings do not actually carry what the instruments sounded like in real life. Especially for classical music as many of the best performances are quite old and recordings techniques weren't what they can be today. For me, I've found that a light hint of euphony (not something gross like an octave worth of bass) can sometimes trick me into accepting that what I hear is, in the overall, a bit more life-like.

    I was speaking from the designer's point of view.
    PS: there might be a way tube amps influence frequency response I forgot and that is output impedance. A lot of OTL tube amps have highish (in between 20 and 150r to shoot from the hip) output impedance and it might interfere with the headphones curves.
  13. bigshot

    I'd be happy to recommend over 8,000 CDs of classical music from the past fifty years that I've checked on a clean, flat solid state system! They all are extremely well recorded and they all sound completely realistic. Do you even listen to classical music, bluegrass or acoustic jazz? All three of these genres are fortunate to benefit from fantastic recording quality and natural sound. Pop vocals. 50s/60s big band, easy listening... there are lots of genres with a wealth of recordings that benefit from accurate playback.

    As for designing amps, I don't want to do that myself. I'm not in this hobby for equipment fetish. I love music. I just want to go out and buy equipment off the shelf that presents my music accurately. I also don't need a headphone amp. My headphones don't benefit from amping, and when I listen to cans, I don't want a bunch of boxes strung together with wires. I just want to plug into my computer or receiver and listen. Besides, most of my serious listening is done with speakers.
  14. 00940
    Yes I do listen to classical music. Mostly baroque vocal music to be accurate. Not a big fan of jazz.
    Thing is... I'm mostly buying based on my tastes wrt who is singing/playing.
    And my most used system is a clean, modern DAC, a solid state amp (Gilmore dynalo) and hd650. I'm not exactly chasing gross euphony.
  15. elmoe
    I listen to a lot of jazz, and a great GREAT deal of recordings are terrible, especially those from the 20s up to the 1950s (and there are quite a lot of them). Try finding a fantastic recording of Art Tatum to name one, or old Louis Armstrong recordings playing blues trumpet (30s-40s recordings). Sure I could listen to newer recordings of modern artists (and I do, or even late Armstrong recordings that are fantastic), but I'm interested in the music first, the recording's quality comes as a far second, and there are a great many recordings of music I enjoy listening to that just don't have the quality I would wish for - and never will. For those, the euphonics of tube amplification work wonders that no amount of careful EQing I've tried has ever come close to (and it wasn't for lack of spending hours EQing things). I like a lot of solo piano and jazz trio works from before the 50s (I have hundreds of recordings from the 20s-50s period) and I can count on one hand the number of those that actually sound good.
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