Wiring an amp

[02ranger]

I just recently acquired a 1976 20' IMP runabout with a slightly modified 350 and the boat is in VERY good shape. All it needs is a kickin system before I can take it to the beach. The wiring for the head unit is already there and I am very familiar with wiring amps and systems in cars, but my main question is: where is the best place to ground the amp in a boat? I would like to mount the amp up under the front dash passenger side so it won't get wet. Normally I don't like to make the ground wires for the amp any longer than 18", but there's not much to ground it to up front. Also, would a capacitor be a good idea? I have a 1 farad cap laying around I could use. I'm going to be using a RF 200watt 4ch, bridged down to 2ch to push 2 JL audio subs. Any help would be great!

[Essex502]

Originally posted by 02ranger
I just recently acquired a 1976 20' IMP runabout with a slightly modified 350 and the boat is in VERY good shape. All it needs is a kickin system before I can take it to the beach. The wiring for the head unit is already there and I am very familiar with wiring amps and systems in cars, but my main question is: where is the best place to ground the amp in a boat? I would like to mount the amp up under the front dash passenger side so it won't get wet. Normally I don't like to make the ground wires for the amp any longer than 18", but there's not much to ground it to up front. Also, would a capacitor be a good idea? I have a 1 farad cap laying around I could use. I'm going to be using a RF 200watt 4ch, bridged down to 2ch to push 2 JL audio subs. Any help would be great!
I have to admit my lack of serious knowledge on killer audio but here's an interesting post on another board about using capacitors:
Truth about Caps and Dogs (http://p205.ezboard.com/fcaraudioknowledgefrm7.showMessage?topicID=33.topi c)
I don't have a clue whether the author is right or wrong but it seems to apply to your question.

[Dr. Eagle]

I have always taked it to the negative battery terminal. I guess you could go to the engine block.

[Havasu Hangin']

Originally posted by 02ranger
where is the best place to ground the amp in a boat?
Since a boat is fiberglass, there is no such thing as a good ground. You need to run it back to the batteries (with the same gauge as the power cable).
Which gauge wire will depend on the length and current draw needs.
Originally posted by 02ranger
Also, would a capacitor be a good idea?
No.

[Scream]

The use of a Cap inline with the hot will only act as a filter for the 60 hz whine you can get from alternator noise. We've used them alot in rf transmitters, but never 1 farrod, usually 200 M uF

[Dr. Eagle]

Originally posted by Scream
The use of a Cap inline with the hot will only act as a filter for the 60 hz whine you can get from alternator noise. We've used them alot in rf transmitters, but never 1 farrod, usually 200 M uF
I have used them as an A/C filter too, not to "stabilize" voltage... although I know some do use them for that.
I usually do install a Ground Bus bar in the rear of the boat and I have used both the engine block and the battery to ground the bar. Then I make sure all of my accessories ground to the same place (busbar) so as not to create any ground loops.
This is (naturally) one of the outstanding projects I haven't done on my Ultra yet. Along with the amps and subs.

[Infomaniac]

WOW nothing like an opportunity to show my ignorance.
The expert that I consulted with when designing Mrs. Infomaniac's boat system said the function of a cap was to discharge during a very big bass note. (I already had the components) There might not be enough energy "volume" so to speak in the wiring ahead of the cap to support the big bass event to it's maximum potential.
Sounded reasonable to me as there were 4 720W amps drawing from the same power source.
Old school 2 years ago technology I guess.

[Havasu Hangin']

Originally posted by Infomaniac
WOW nothing like an opportunity to show my ignorance.
The expert that I consulted with when designing Mrs. Infomaniac's boat system said the function of a cap was to discharge during a very big bass note. (I already had the components) There might not be enough energy "volume" so to speak in the wiring ahead of the cap to support the big bass event to it's maximum potential.
Sounded reasonable to me as there were 4 720W amps drawing from the same power source.
Old school 2 years ago technology I guess.
The key to remember that a cap must be recharged. Therefore, any positive benefits of having a storage source "closer to the amp" in negated.
Add to that the fact has a ESR value (which will draw current)...and a cap becomes an expensive terminal block.
Richard Clark did a cap test awhile back which showed no value in the system...I'll see if I can dig it up.

[Infomaniac]

I thought the cap might recharge once the bass note that needed the boost was gone.
Don't they discharge and charge instantly? I can see a system drawing maximum potential from the wiring all of the time would not give the cap enough time to recharge.
Not argueing just discussion.
If the objective of the cap was to make up for insufficient source power, I can understand it does not work.
What if the system has enough but just needs a quick boost occationally? Just that extra bit for an instant. That is why I put them in.
I ran welding cable from the battery to the power/ground blocks. From there 4 amps. One for each speaker. For the 2 sub amps, each a 1 farad cap. Same engineer as the beer can grill.
They are handy to be able to look under and see what the battery voltage is. :D :D
Should have this thread in the stereo forum.

[riverbound]

We always run the same power and ground to wherever the amps are form the batteries (the positive side usually goes to the perko) There are no good grounding points in a boat. So the best you will find is at the batteries.
A cap in a car does help with keeping the voltage constant, because you have so many different devices pulling from the electrical system when it is running. But in a boat the motor usually is not running when the system is being played therefor the only thing drawing from the electrcal system is the stereo. Caps are a waste of money in a boat. Spend the money you would have spent on a cap on more batteries.

[Infomaniac]

My discussion is not to get folks to buy caps. Just trying to justify mine. :D :D
02Ranger already has one lying around. Does it hurt to install it?

[ROZ]

Originally posted by Havasu Hangin'
Richard Clark did a cap test awhile back which showed no value in the system...I'll see if I can dig it up.
Wierd... Richard Clark is listed as one of the few who helped develop serveral items in the Monster cable lineup. Their caps being one of them... How ironic... :D

[Havasu Hangin']

Originally posted by ROZ
Wierd... Richard Clark is listed as one of the few who helped develop serveral items in the Monster cable lineup. Their caps being one of them... How ironic... :D
Isn't he one of the first one to use them in competition in the early 80's? Now he admits they have no value in car audio.
How ironic.
Caps are one of those "the competition guys are using them...so it must work"...circumstances. These days, it seems the only guys saying how great they are...are the guys selling them.
How ironic.

[Cheap Thrills]

Originally posted by Infomaniac
My discussion is not to get folks to buy caps. Just trying to justify mine. :D :D
02Ranger already has one lying around. Does it hurt to install it?
It wouldnt hurt at all IMO . I wonder how many component level tecs are answering these electronics threads ? .
by component level I dont mean part swappers .
look inside any amp. made and the first part of the power circuit consist of caps. one reason they are there is to take the ripple off the current . regulation , and to supply the amp with a "reserve " ammount of current for inst. peak loads .
heres another way to look at it also . a cap is just a dry battery in a few words .
now if your battery is healthy and the power cable you run is heavy enough to carry the load (current) that the amplifier demands , what more capasitance could you need other than your 700cca marine battery ? .
It's all preference .
C.T. :wink: