using a lower amperage fuse

My amplifiers manual on page 11 (link: http://www.pioneerelectronics.com/PUSA/Unassigned+Content/GM-D7500M+OWNERS+MANUAL) states that it uses only 18A at continous power. However it comes with a 40A fuse. Is it ok to replace it with a 25A? I've already had one of these amps blow (taking my sub with it), so I returned it to the seller and bought another sub. I'm just waiting to get my replacement amp from the seller. The fuse did not protect my amp, neither the 40A maxi in my power line, or the 40A on the amp blew but my amp still somehow managed to blow. Should I try a 25A?Pioneer DEH200UB

Single Pioneer GM-D7500M

Single Pioneer Premier TS-W1008D4

Do not use a different fuse size from what is specified by the manufacturer.  The fuse is not designed to protect your subs, it is designed to protect the amplifier.  How did you "blow" the previous amp?Support the12volt.com

I know that it doesn't protect the subs. Anyway, I bought the parts in my sig from Sonic Electronix. I had them "professionally" installed at a local car audio shop. They didn't set the gain on the amp properly (Left it at .65V when my HU is 2V), and after a couple of ours of playing music loud, the fuse on the amp blew. Replaced the fuse, and it would only play at very low volume levels (HU would have to be at 11 out of 62 for the amp to be able to play) or it would go into protect mode. I thought my sub had blown, so I hooked up a spare sub I had and amp would also go into protect mode. Put the original sub and a spare Boss amp I have and the sub would also cause the Boss to go into protect. Now, I don't know if it was a bad voice coil on my sub that blew everything or if it was the gain on my amp, but anyway, they both blew. Sonic doesn't warranty blown subs so I just ordered a new one. It came in, and my system for the moment is the Boss amp and the new Pioneer sub. Waiting for the RMA back from Sonic on my amp. By the way, I went back to the audio shop, demanded a refund (and got it) and I will no longer to any more business with them. I know how to install systems, but at that time I was extremely busy with school and work so I didn't really have time, that's why I got them to do it. Other pertinent info: Headunit - Pioneer DEH200UB Amp - Boss D1200M (The blown one was Pioneer GM-D7500M) Sub - Pioneer Premier TS-W1008D4 (Same as the one that blew) Scosche - 6 gauge power and ground (Power- 7ft, Ground- 2ft) Battery - 8 month old Duralast Gold Car - 2003 Chevy Silverado 1500 Single Cab (Stock alternator)Pioneer DEH200UB

Single Pioneer GM-D7500M

Single Pioneer Premier TS-W1008D4

Also, I forgot to mention that my sub is and was wired parallel for 2Ohm load. Now, quick question, why would Pioneer include that info on their amp manual? I'm kind of inclined to still try the smaller fuse, and if it blows them too much, jump to a 30, then if that doesn't work, 35 and so on until I get back to 40 (if I ever do).Pioneer DEH200UB

Single Pioneer GM-D7500M

Single Pioneer Premier TS-W1008D4

Wow, that's all I have to say, wow. I could not freaking understand it until now. Thanks a lot man, no wonder your a Mod here. I hope you don't mind if I ask you a few more questions. So for sure it was the sub that blew first? If the sub blew AND the amp blew, why would they still play at low volumes? Do you think I should have faith on that particular sub and amp again in the future? Could there have been any other factor other than the gain and/or clipping to cause this? What experience or feedback can you give me on Pioneer amps and subs? I'm not after making people look at me, or after the VERY best sound quality, since I cannot afford that right now.Pioneer DEH200UB

Single Pioneer GM-D7500M

Single Pioneer Premier TS-W1008D4

Not wanting to contradict DYohn - and DYohn may know better in this case etc - but usually reducing the fuse size is not a problem. However even if it were only an despite being an 18A load normally, it may have a much larger fuse. Reasons include....: - general rule - Fuses normally loaded at not more than ~70%; hence 18/.7 = 25A fuse; - 18A may be at 13.8V or 14.4V etc; that's 260W if 14.4V which means 21.6A@12V or 26A@10V etc - whatever the lower limit of operation is; - there may be higher inrush/start-up currents; - other allowable peaks may exceed 18A; - etc etc etc.... Then there is "discrimination" or how fast a fuse reacts. A typical fuse might tolerate 100% current for 1 hour, or many minutes etc, or 200% for 5 seconds, and may hence be too slow to protect internal components (especially output semiconductors).    There are slo-blo & fast-blow fuses, and those with special "blow profiles" - though this is more common for circuit breakers. But as to why your equipment blew - I'd say DYohn covered it. My ramble above deals more with protection/fusing in general. DYohn pointed out the specific current draws under different amp configurations.

Using a smaller than rated fuse can only better protect your equipment. 

So what is the proper way of setting amp gains, Im an amatuer installer and wanna make sure I prevent blowing up any equipment??Mastermindz