Adding another amp...how to wire?

[jt1989]

I decided to add a mb quart 640w 4 channel amp to my sound system. I currently have a 8g power wire from the battery, fused, and to the amp...I know Ill have to go to a larger power wire if I use a distribution block...planning on 4g to the distribution block, then 8g to each amp...will this be a large enough setup for the power cables? Also, for grounding the amps, can I use a distribution block as well? Same setup without a fuse obviously. I am planning on running the ground cables to the battery as well. Thanks in advance!

 

[haulnazz15]

Re: Adding another amp...how to wire?

The 4ga to block, and 8ga to amps will be fine. I don't know how long of a run it is from the amps to the battery, but I'd run the grounds to the engine block (or other suitable grounding site) instead of the battery. The battery is grounded there anyway.

 

[Silvertip]

Re: Adding another amp...how to wire?

The engine is NOT the central ground point on a boat. The NEGATIVE terminal of the battery IS the ultimate ground.

 

[H20Rat]

Re: Adding another amp...how to wire?

Wire gauge is useless without the distance also. 8 gauge might be fine, but if the total run (positive and ground added together) is something like 50 feet, even 4 gauge is too small.

 

[H20Rat]

Re: Adding another amp...how to wire?

The engine is NOT the central ground point on a boat. The NEGATIVE terminal of the battery IS the ultimate ground.

Depends... Is the engine running or turned off? With the engine running, the alternator (and therefore engine block, more or less) is the ultimate ground. The amp's power is coming from the alternator, not the battery. The battery is a mere load in the grand scheme of things. If you are drawing enough power to drop the voltage down to where the battery is no longer charging and is providing power, it means you need to upgrade alternators.

Key off, obviously its the battery.

I've designed some LARGE boat systems, the last one topped out over 4000 watts of power. (20+ speakers total) I generally will ground to the battery, because I'm going for the worst case scenario. If I knew the person was going to use the system almost exclusively with the engine running, and I was going for the absolute loudest system, I'd go to a ground bolted right to the alternator mount.

 

[jt1989]

Re: Adding another amp...how to wire?

If I ran the positive and negative to the battery the total run would be about 30ft. 15ft posivitve 15ft negative...should I upgrade to larger wire with this distance? I really want to ground to the battery to keep the bilge around the engine as wire free as possible

 

[mark1905]

Re: Adding another amp...how to wire?

Don't combine the two run lengths together to get total length.. look at each section. You have a 15ft run length.

If you're only pushing 4 ohms per channel on the MB Quart amp, then 8AWG per 15ft section is fine. If you're wanting to put two amps in the same area, then run 4AWG up to a distribution block and split it into two 8AWG cables. You'll be ok. You should always use the same gauge wires for both positive and negative electrical connections. So, repeat this for both the positive and ground cables. Two distribution blocks. Should you decide to add speakers and push the amps to 2 ohms per channel, you'll need to step up to 4AWG cable per amp.

Whenever you can, ground directly to the battery. All you're doing by grounding to the engine is adding resistance by making the power travel through the block and back up the ground cable to the battery. The shortest, most direct, cleanest route is always the best one.

It's all really very simple stuff..


PS.. Good choice on the MB Quart amps..! Best bang for your buck in a marine amplifier.. period..

 

[bruceb58]

Re: Adding another amp...how to wire?

Don't combine the two run lengths together to get total length.. look at each section. You have a 15ft run length.

To get the total voltage drop he needs to calculate using the total length. What if he had a postive lead of 1 foot and a negative lead of 29 feet? That would be the same voltage drop as 15' and 15'.

 

[mark1905]

Re: Adding another amp...how to wire?

To get the total voltage drop he needs to calculate using the total length. What if he had a postive lead of 1 foot and a negative lead of 29 feet? That would be the same voltage drop as 15' and 15'.

Touche.

Since we're installing on a boat, both wires are going to be the same length. A 15' run length of both wires with the power that the NAU460 draws requires an 8AWG wire @ 4ohms.

 

[Richline]

Re: Adding another amp...how to wire?

Added new head and 2 amps, sounds great until I turn on the ignition. How do I fix

 

[bruceb58]

Re: Adding another amp...how to wire?

Added new head and 2 amps, sounds great until I turn on the ignition. How do I fix

Should start your own thread instead of adding to this one. Will get way more responses.