Συγνώμη, έπρεπε να είμαι πιο συγκεκριμένος... Συμπληρώνω: για να προστατέψει τους πυκνωτές του power supply στην εκκίνηση του ενισχυτή (power on).
"If you're wondering why all those old amps use a standby switch, its because Fender was designing complicated amps on the cheap. In the bigger versions of the Bassman, money was saved by using power supply caps that were rated only for the working voltage, not the peak voltage which occurred before the valves start drawing current. As everyone knows, Marshall simply copied the Bassman without a second thought, complete with standby switch, so now we have the two biggest names in the industry using standby switches, and the rest is history. The other big players, Vox and
Gibson, never used standby switches since they didn't need them. Only very recently have they started adding them, purely because too many guitarists want their amp to look just like a Fender/Marshall, even though nowadays no designer (who values his reputation) uses underrated capacitors." Mr Blencowe
"Most standby switches simply turn the HT on and off, allowing the amp to be muted while the valves are still idling hot. When the standby is switched to "on" all the power supply capacitor will instantly draw inrush current;- this 'hard switch on' and inevitably shortens the working life of the rectifier and capacitors." Mr Blencowe, again...
"In a properly designed amp, a standby switch is nothing more than an expensive, oversized mute switch." and again Mr Blencowe
Συγνώμη για τα αγγλικά αλλά προτιμώ "να κάνω quote" απευθείας...