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Blues distortion? Made by overdriving preamp and power tubes a little, enough to just start compressing the peaks of the waveforms, and not very much high frequency content, by electronically cutting highs or running the signal into a speaker cab that acoustically cuts highs.
Guitar Player magazine ran a construction article on this very topic, modifying a Fender Bassman to be the "Ultimate Blues Machine". The article ran in 1995, authored by John McIntyre.
A recently voiced although intuitively applied idea in distortion is that tube distortion sounds best when each successive distortion stage is overdriven by less than about 12db. This has the effect of
keeping the tubes inside the area where the signal is more compression-distorted than clipped. That is what those resistive divider chains between distortion stages are for inside those distortion preamp schematics. Mesa's distortion preamps are another good example.
Overdriving a tube stage too much gives you harsher clipping, not the singing, sweet distortion we want. To really get sweet, crunchy distortion,
keep each stage that goes into distortion no more than 6-9db into distortion. Marshall/metal/Boogie/etc. distortion? Made by massively overdriving preamp tubes until the original waveform is massively compressed and clipped. Usually followed with a moderate amount of high frequency cut to remove some of the "insect attracting" overtones generated in the clipping process. There is commonly some output tube overdrive in this process, too.
Good distortion at low(er) volumes? overdrive preamp tubes until you get the clipping you want, then feed a limited amount of this to a power amp stage to get the loudness you want. This is how master volume controls work."
- извиняюсь за эту длинную цитату, но тут есть очень здравая мысль, которую я
выделил: покаскадная балансировка в зоне мягкой компрессии для получения именно блюзового звука. Наращивая число каскадов можно растянуть эту, в общем-то, довольно узкую зону. Идея именно в этом. А разноразмерные аттенюаторы призваны избавить эффект от монотонной механистичности обработки. Возможно, их номиналы не вполне оптимальны, но сама по себе идея очень и очень привлекательна.
