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Meine 65' Twin Reverb Reissue Mods

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Nigel:

--- Zitat von: jacob am 17.10.2012 15:22 ---

da hast Du wohl ganz offensichtlich (evtl. in einem US- Amp- Forum?) was verkehrtes gelesen  oder es vielleicht, im Laufe der Zeit, einfach verwechselt  ???


--- Ende Zitat ---

Nene, Info kommt von nem Kollege, der einen Bachelor ??? in Elektrotechnik hat.....halt kein Meister...mmmhh, gibts n Satz heisse Ohren. Ich konsultiere nochmal seine Springer-Bibliothek.

Für alle Quellen bin ich Dankbar! Immer her damit.

Gruß,

Nigel

jacob:
Nachlesen kann man das z.B. hier:

http://www.hameg.com/downloads/fachartikel/HAMEG_Rauschen.pdf

und auch hier:

http://www.elektronikinfo.de/strom/widerstandsrauschen.htm

EDIT:

und natürlich auch hier:

http://aikenamps.com/ResistorNoise.htm

Gruß

Jacob

sjhusting:
Found it. It's about ripple, though.

http://www.ampbooks.com/home/classic-circuits/class-AB-ripple/

jacob:
Super, vielen Dank für Deine Mühe!

Besonders interessant und sehr aufschlussreich bzgl. "Verschlimmbesserung beim Netzteil" finde ich:

"For Project WILDCAT a vacuum-tube voltage regulator with a controllable internal resistance was designed to substantially reduce AC ripple but retain the same power supply sag characteristics, particularly the dynamic nature of the all-important screen supply voltage. "


"The Big Surprise

The Project WILDCAT team summarizes the results this way:

"In spite of the practically identical voltage curves (with the exception of the 100Hz ripple), in terms of sound the amplifier is no longer recognizable. Its tonal characteristics are completely different."

Touch sensitivity - zero. Crisp dynamic overtones - zero. As Schmidt and Westphal put it, the WILDCAT became more like a kitty cat. The new power supply had filtered out more than just noise. It had suppressed the heart and soul of the amplifier!

Since the low-noise power supply had an adjustable source resistance, enabling the amount and rate of sag to be controlled, the team experimented with it a bit. They observed that when sag was eliminated, the amp sounded "limp" and "cheap," like a String 300 transistor amp from an electronics discount store. Nevertheless, even with the proper amount of sag, something was definitely missing from the Bassman's legendary sound.

Conclusions

The WILDCAT team concludes that AC ripple present in the power stage represents much more than just noise. Its modulation of the output appears to have a significant effect on the Bassman's sonic character.

As important as this result is in itself, the team goes on to conclude that if ripple is tonally significant, then a difference in AC line frequency (60Hz in the US and 50Hz in Europe, for example) also has an important impact. Converting between 120 and 230 volts is not difficult. Converting between 50 and 60 Hertz to achieve a particular tone dynamic is a whole different story!"

Gruß

Jacob
 

sjhusting:

--- Zitat von: jacob am 17.10.2012 16:13 ---As important as this result is in itself, the team goes on to conclude that if ripple is tonally significant, then a difference in AC line frequency (60Hz in the US and 50Hz in Europe, for example) also has an important impact. Converting between 120 and 230 volts is not difficult. Converting between 50 and 60 Hertz to achieve a particular tone dynamic is a whole different story!"

--- Ende Zitat ---
Neil Young would agree, which is why he brings his own 60-hz generators to Europe.

s.

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