Using Fuse Size To Determine Amp Wattage

belangers wrote: The manufacture always fuses 20% over the rms rating of an amplifier.

Interesting information. How have you came to this determination? Is there some sort of agreement between EVERY company that manufactures amplifiers? Why 20% and not 21%? If the fuse is not 20% over the rms rating of the amp is there a fine or penalty that holds the manufacturer accountable for their improper sizing?Kevin Pierson

DYohn wrote: belangers wrote: I have more experience in this field than most, and have seen it all. You might want to check the profiles of some of our regular members here before you start making statements like that.  :)  Also, you may have been an installer for a few years, but on this forum you're still a noob.

Dyohn: Just in case... Since 1973, sound system and loudspeaker designer and engineer for several audio and video related companies and manufacturers, including Oberheim, Harbinger, Sony, Ampex, Bag End, Creative Labs, Lucasfilm/THX, Precision Audio, and Tyco. Also worked as a video producer and sound designer for Columbia Pictures, Arista Records, A&M Records, MTV and The California Music Channel. Worked in several capacities for broadcast radio and television stations, and for ten years owned my own video production company. Current owner of Four Winds Audio in San Jose, CA. Education: PhD in Cybernetic Systems from the University of California. Also a BSEE in acoustics and an MA in Broadcast Communications. University Professor in Radio and TV and in Communications at San Jose State University and Santa Clara University in California from 1990-1996.M.E.C.P & First-Class

Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

Noting that the thread title is about determining amp wattage for the fuse size... And that almost all fuses will operate all day at a 110% overload... But that "80% rule" is pretty much right. (I sometimes write 70%, but that's more for general wiring and loads, else just wrong.) I only glance quickly at the previous replies and I suspect some cases of omission, taking too literally, and rewording in retrospect. Fusing is to protect the battery and the vehicle and the downstream wiring (that's included in "the vehicle"). Modern vehicles are set for up to 14.4V. 14.2V is probably the norm. Long gone are the days of 13.8V. I can see the engineering -cum- economic reason for matching distribution sizes, but I also see the engineering -cum- design reason for overrating the distribution - ie, to minimise voltage drops to the load. I prefer the latter. (But I cannot understand how a 3V drop is considered "the max acceptable" the typical things we like to modify.) And not that I understand yet why so many SMPS amps behave like resistive loads. (I haven't yet deciphered my Kicker SMPS configuration, but it uses a typical SMPS chip.) But that's another story. I would probably never use such a primitive system if I were into performance amplification (ie, the SMPS integral to remote amps). This could be an interesting discussion...