PPI ProMOS 425 1/2 ohm stable?

Ryan from Ohio · Post by **Ryan from Ohio** » Sun Jul 27, 2008 10:50 am

That fuse rating must be wrong...

25a X 13.8V = 345 WRMS total... not accounting for efficiency loss (about 55-60% real world.

If the specs are correct:

800 wrms / 13.8= 58 amps... Now account for inefficiency...

58 X 1.4 = 81 Amps. Go with an 80 Amp fuse.

Tim · Post by **Tim** » Sun Jul 27, 2008 4:53 pm

If you are getting a good price go for it. The pro mos was the top of the line in the ppi stable. I didn't get any hands on with the pro mos but I did have a art series A-600 that I ran 4-4ohm 10's off of. I ran it at that load for quite some time and it never gave me any problems. It got warm but where it was located in my wrangler it was kept cool.

It may not be 1 ohm stable but it will be a very solid amp for your application. I agree with ryan, my A-600 had a 40 watt fuse in it, and it blew it a couple times. The 25 amp fuse won't be enough.

Tim

Tim · Post by **Tim** » Sun Jul 27, 2008 4:57 pm

Ryan from Ohio wrote:That fuse rating must be wrong...
25a X 13.8V = 345 WRMS total... not accounting for efficiency loss (about 55-60% real world.
If the specs are correct:
800 wrms / 13.8= 58 amps... Now account for inefficiency...
58 X 1.4 = 81 Amps. Go with an 80 Amp fuse.

Hey ryan, I pretty much got all the math down on your equation but where does the 1.4 come from??

Tim

Bwcad1 · Post by **Bwcad1** » Sun Jul 27, 2008 6:05 pm

for referance class D typical efficency 80% class a 55%

loudwagon15s · Post by **loudwagon15s** » Sun Jul 27, 2008 6:35 pm

Bwcad1 wrote:for referance class D typical efficency 80% class a 55%

wow, i didnt know that there was that big of a difference

Ryan from Ohio · Post by **Ryan from Ohio** » Mon Jul 28, 2008 3:01 am

Ya I calculated it out at 60% efficient.

Its probably anywhere from 60-50%. So I gave it the credit

Tim · Post by **Tim** » Mon Jul 28, 2008 11:14 am

[quote="Ryan from Ohio"]Ya I calculated it out at 60% efficient.
Its probably anywhere from 60-50%. So I gave it the credit ]

I still don't know where the 1.4 came from

Tim

Fishy · Post by **Fishy** » Mon Jul 28, 2008 2:13 pm

I think PPI deliberately shipped their products with "small" fuses to protect their products. My ProMOS 2050 came with a 35 amp fuse(hard to find btw). I had it bridged into a pair of 10w5's for a 2ohm load and a theoretical 400 watt capability. I never had a problem until I let a friend drive my Cherokee. He said he liked the way it sounded until the bass quit(he blew that fuse of course).

Wow. Some people don't know the difference between music and noise. I set my gains accordingly now.

BTW I got the 425 for $325 shipped and have a project in mind where I might just blow that 25 amp fuse.

Fishy · Post by **Fishy** » Mon Jul 28, 2008 2:19 pm

Ryan from Ohio wrote:That fuse rating must be wrong...
25a X 13.8V = 345 WRMS total... not accounting for efficiency loss (about 55-60% real world.
If the specs are correct:
800 wrms / 13.8= 58 amps... Now account for inefficiency...
58 X 1.4 = 81 Amps. Go with an 80 Amp fuse.

Yeah its really wrong. I'm assuming the 425 has a regulated power supply like my 2050 which if I'm not mistaken drops the efficiency down even further.

I'll probably start with 25 amp fuse and gradually work my way up. The only time I really crank things is when I'm trying to impress my friends and lately most of them are impressed with SQ over SPL. We are gettng old I guess.

-Dwight

cargodz · Post by **cargodz** » Mon Jul 28, 2008 4:27 pm

^Funny cause the older I get the more I get into SPL... But I guess you guys haven't reached the hearing loss stage yet

LOL