I want to design or find a design for a limiter to put just before my power amplifier, so that the output voltage is kept below some safe maximum value for the speaker I am using. Clipping with diodes is the easiest option, but I'd like something a little smoother, that would, for example, imitate the action of some tube guitar amps in gradually reducing gain at high output levels so that the waveform is rounded off rather than hard-clipped. I'm leaning toward using a Jfet to do this job, in a configuration based on the usual/classic fet limiter or compressor circuit where it forms the bottom half of a voltage divider and shunts away some of the signal when it's turned on. Unlike classic compressor circuits, though, I want a very fast (essentially zero) attack time, and am willing to tolerate quite a bit of distortion when the limiter is limiting -- although none or very little when it is not.
Does anyone know of such a circuit? Does anyone have design ideas or principles you think I should be keeping in mind?
Does anyone know of such a circuit? Does anyone have design ideas or principles you think I should be keeping in mind?
You don't need or want a zero attack for speakers. They take a long time to burn up.
You want a significant frequancy bias for most hi-fi speakers, because the woofer coil is 2 inch and the tweet coil is 3/4".
Protecting woofers against over-excursion is even more complicated.
Alto it limits your choices, IMHO the best plan is to over-provision your drivers so they do not strain at desired output (whatever that is).
In guitar amps, the player WILL distort the amp. For-guitar speakers are designed to take the full square-wave power (a "30W" speaker will eat 50W of heat intermittently all night).
You want a significant frequancy bias for most hi-fi speakers, because the woofer coil is 2 inch and the tweet coil is 3/4".
Protecting woofers against over-excursion is even more complicated.
Alto it limits your choices, IMHO the best plan is to over-provision your drivers so they do not strain at desired output (whatever that is).
In guitar amps, the player WILL distort the amp. For-guitar speakers are designed to take the full square-wave power (a "30W" speaker will eat 50W of heat intermittently all night).