Tube microphones are chosen when the particular distortion of tubes is wanted by the recording engineer to get the effect he wants. Tube distortion is sometimes below audibility. Choosing to use tubes at home, in many implementations, is to add some effects to the sound you like, very, very different from the recording engineer's reason to use them.
I don't get it. Everything which brings a "colour" including overload/saturation, or whatever you may call it, is actually changing the input signal, which is the definition of distortion : "falsified reproduction of an audio or video signal caused by change in the wave form of the original signal"
You are basically repeating false narratives attributed to vacuum tubes. Just like any other active device tubes exist in a circuit, not alone, hence one circuit can be made to do something or sound different from another. This is not just the active device, it is how it is used that can cause differences people speak of. For people to fully understand audio electronic IMO they need to understand vacuum tubes. I feel sad for engineers that don't.
Good point, but don't you think the overload characteristics and transient capabilities, not just "effect" can be a factor also? I do not consider a U87 colored.
Circuits that do not have adjustable "bias" are self-biasing.
My comment is not specific to tubes. It is just stating the definition of distortion which is : altering the input signal... So yes, if a tube changes the waveform, this a distortion of the input signal. That is just THE definition. There is no judgement of value here as distortion is not necessarily a bad thing (as in guitar amps)..
That's the difference between music production and music reproduction. In music production, one is attempting to create a pleasing sound and that is often achieved through euphonic distortion, non-linearities, etc.
If that were the case, then you would not hear differences by changing from Mullard to Sylvania to Svetlana tubes of the same type. You can't have it both ways; that you can hear differences between tubes but tube distortion is below the threshold of audibility.
Tubes can't drive speakers at all, which is why you need output transformers on tube amps. It's those output transformers that lead to tube amps having a low damping factor and interacting with reactive loads far more than do good solid state amplifiers.
There are OTL amps. Harold Beveridge actually built a speaker with a dedicated OTL amp.
Tube guitar amps also rely on tube microphonics to create a kind of feedback loop which also helps with "tone".
I am aware of OTL tube amps, but it's like saying that bicycle tires are suitable for cars -- you just need lots of them in parallel. The Atma-Sphere S30 Mark 3.2 OTL tube amp produces 30 watts per channel into 8Ω load and needs five output tubes per channel to do it, drawing 400 watts of power from the AC lines. They are serious about requiring an 8Ω speaker, with their manual warning not to use any speaker that drops below 8Ω at any point (almost all 8Ω speakers dip well below that). From their manual:
Atma-Sphere said:
Still called distortion....
The problem with valve power amps isn't just the valves it is the output transformer. There are probably no transformers which perform well over the entire audible frequency bandwidth since what is required for good performance at low frequencies may compromise the performance at high frequencies and give early roll off. Having written that, even solid state stuff with inter stage transformers can sound "nice" so maybe the distortion/ addition/ removal of some of the signal by a transformer is something people like????
There are no non-inductive output transformers, either, which means that even if the transformer were to have linear frequency response into a purely resistive load, it's not going to be linear into a reactive load like a speaker's crossover.
Many times people use various components as tone controls to offset everything from room acoustics to speaker non-linearities. One thing I noticed early on in the CD era was people complaining that CDs sounded "thin" and lacked "warmth"; on their systems, their LPs sounded better. They had tuned their systems around a turntable that picked up bass microphonically through the air and through the floor. If they had a truly linear frequency response, the turntable would have had a boomy bass due to that bass feedback loop within the listening room.
Very true, and also many popular cartridges had/have a rolled off top octave or more, so speakers to compensate for that sound thin with a flat source.
Henry Kloss, of Advent and KLH fame, remarked that he made a tweeter with much better performance than what his speakers shipped with, but it exacerbated hiss, ticks, and pops to much as to be unlistenable. Interestingly, in the KLH 17 tweeters had a perforated metal grill adhered to them. Removing that yields a much more extended, satisfying HF response (with modern amplification and sources).
